    // Copyright (C) 2005  Davis E. King (davis@dlib.net), Keita Mochizuki
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_BASE_WIDGETs_CPP_
    #define DLIB_BASE_WIDGETs_CPP_

    #include <iostream>
    #include <memory>

    #include "base_widgets.h"
    #include "../assert.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
        // button object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        void button::
        set_size (
            unsigned long width,
            unsigned long height
        )
        {
            auto_mutex M(m);
            rectangle min_rect = style->get_min_size(name_,*mfont);
            // only change the size if it isn't going to be too small to fit the name
            if (height >= min_rect.height() &&
                width >= min_rect.width())
            {
                rectangle old(rect);
                rect = resize_rect(rect,width,height);
                parent.invalidate_rectangle(style->get_invalidation_rect(rect+old));
                btn_tooltip.set_size(width,height);
            }
        }

    // ----------------------------------------------------------------------------------------

        void button::
        show (
        )
        {
            button_action::show();
            btn_tooltip.show();
        }

    // ----------------------------------------------------------------------------------------

        void button::
        hide (
        )
        {
            button_action::hide();
            btn_tooltip.hide();
        }

    // ----------------------------------------------------------------------------------------

        void button::
        enable (
        )
        {
            button_action::enable();
            btn_tooltip.enable();
        }

    // ----------------------------------------------------------------------------------------

        void button::
        disable (
        )
        {
            button_action::disable();
            btn_tooltip.disable();
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_tooltip_text (
            const std::string& text
        )
        {
            btn_tooltip.set_text(text);
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_tooltip_text (
            const std::wstring& text
        )
        {
            btn_tooltip.set_text(text);
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_tooltip_text (
            const ustring& text
        )
        {
            btn_tooltip.set_text(text);
        }

    // ----------------------------------------------------------------------------------------

        const std::string button::
        tooltip_text (
        ) const
        {
            return btn_tooltip.text();
        }

        const std::wstring button::
        tooltip_wtext (
        ) const
        {
            return btn_tooltip.wtext();
        }

        const dlib::ustring button::
        tooltip_utext (
        ) const
        {
            return btn_tooltip.utext();
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_main_font (
            const std::shared_ptr<font>& f
        )
        {
            auto_mutex M(m);
            mfont = f;
            set_name(name_);
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_pos (
            long x,
            long y
        )
        {
            auto_mutex M(m);
            button_action::set_pos(x,y);
            btn_tooltip.set_pos(x,y);
        }

    // ----------------------------------------------------------------------------------------

        void button::
        set_name (
            const std::string& name
        )
        {
            set_name(convert_mbstring_to_wstring(name));
        }

        void button::
        set_name (
            const std::wstring& name
        )
        {
            set_name(convert_to_utf32(name));
        }

        void button::
        set_name (
            const ustring& name
        )
        {
            auto_mutex M(m);
            name_ = name;
            // do this to get rid of any reference counting that may be present in
            // the std::string implementation.
            name_[0] = name_[0];

            rectangle old(rect);
            rect = move_rect(style->get_min_size(name,*mfont),rect.left(),rect.top());
            btn_tooltip.set_size(rect.width(),rect.height());

            parent.invalidate_rectangle(style->get_invalidation_rect(rect+old));
        }

    // ----------------------------------------------------------------------------------------

        const std::string button::
        name (
        ) const
        {
            auto_mutex M(m);
            std::string temp = convert_wstring_to_mbstring(wname());
            // do this to get rid of any reference counting that may be present in
            // the std::string implementation.
            char c = temp[0];
            temp[0] = c;
            return temp;
        }

        const std::wstring button::
        wname (
        ) const
        {
            auto_mutex M(m);
            std::wstring temp = convert_utf32_to_wstring(uname());
            // do this to get rid of any reference counting that may be present in
            // the std::wstring implementation.
            wchar_t w = temp[0];
            temp[0] = w;
            return temp;
        }

        const dlib::ustring button::
        uname (
        ) const
        {
            auto_mutex M(m);
            dlib::ustring temp = name_;
            // do this to get rid of any reference counting that may be present in
            // the dlib::ustring implementation.
            temp[0] = name_[0];
            return temp;
        }

    // ----------------------------------------------------------------------------------------

        void button::
        on_button_up (
            bool mouse_over
        )
        {
            if (mouse_over)
            {
                // this is a valid button click
                if (event_handler.is_set())
                    event_handler();
                if (event_handler_self.is_set())
                    event_handler_self(*this);
            }
            if (button_up_handler.is_set())
                button_up_handler(mouse_over);
            if (button_up_handler_self.is_set())
                button_up_handler_self(mouse_over,*this);
        }

    // ----------------------------------------------------------------------------------------

        void button::
        on_button_down (
        )
        {
            if (button_down_handler.is_set())
                button_down_handler();
            if (button_down_handler_self.is_set())
                button_down_handler_self(*this);
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
        // draggable object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        draggable::~draggable() {}

    // ----------------------------------------------------------------------------------------

        void draggable::
        on_mouse_move (
            unsigned long state,
            long x,
            long y
        )
        {
            if (drag && (state & base_window::LEFT) && enabled && !hidden)
            {
                // the user is trying to drag this object.  we should calculate the new
                // x and y positions for the upper left corner of this object's rectangle

                long new_x = x - this->x;
                long new_y = y - this->y;

                // make sure these points are inside the draggable area.
                if (new_x < area.left())
                    new_x = area.left();
                if (new_x + static_cast<long>(rect.width()) - 1 > area.right())
                    new_x = area.right() - rect.width() + 1;

                if (new_y + static_cast<long>(rect.height()) - 1 > area.bottom())
                    new_y = area.bottom() - rect.height() + 1;
                if (new_y < area.top())
                    new_y = area.top();

                // now make the new rectangle for this object
                rectangle new_rect(
                    new_x,
                    new_y,
                    new_x + rect.width() - 1,
                    new_y + rect.height() - 1
                );

                // only do anything if this is a new rectangle and it is inside area
                if (new_rect != rect && area.intersect(new_rect) == new_rect)
                {
                    parent.invalidate_rectangle(new_rect + rect);
                    rect = new_rect;

                    // call the on_drag() event handler
                    on_drag();
                }
            }
            else
            {
                drag = false;
                on_drag_stop();
            }
        }

    // ----------------------------------------------------------------------------------------

        void draggable::
        on_mouse_up (
            unsigned long ,
            unsigned long state,
            long ,
            long
        )
        {
            if (drag && (state & base_window::LEFT) == 0)
            {
                drag = false;
                on_drag_stop();
            }
        }

    // ----------------------------------------------------------------------------------------

        void draggable::
        on_mouse_down (
            unsigned long btn,
            unsigned long ,
            long x,
            long y,
            bool
        )
        {
            if (enabled && !hidden && rect.contains(x,y) && btn == base_window::LEFT)
            {
                drag = true;
                this->x = x - rect.left();
                this->y = y - rect.top();
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
        // mouse_over_event object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        mouse_over_event::~mouse_over_event() {}

    // ----------------------------------------------------------------------------------------

        void mouse_over_event::
        on_mouse_leave (
        )
        {
            if (is_mouse_over_)
            {
                is_mouse_over_ = false;
                on_mouse_not_over();
            }
        }

    // ----------------------------------------------------------------------------------------

        void mouse_over_event::
        on_mouse_move (
            unsigned long ,
            long x,
            long y
        )
        {
            if (rect.contains(x,y) == false)
            {
                if (is_mouse_over_)
                {
                    is_mouse_over_ = false;
                    on_mouse_not_over();
                }
            }
            else if (is_mouse_over_ == false)
            {
                is_mouse_over_ = true;
                if (enabled && !hidden)
                    on_mouse_over();
            }
        }

    // ----------------------------------------------------------------------------------------

        bool mouse_over_event::
        is_mouse_over (
        ) const
        {
            // check if the mouse is still really over this button
            if (is_mouse_over_ && rect.contains(lastx,lasty) == false)
            {
                // trigger a user event to call on_mouse_not_over() and repaint this object.
                // we must do this in another event because someone might call is_mouse_over()
                // from draw() and you don't want this function to end up calling
                // parent.invalidate_rectangle().  It would lead to draw() being called over
                // and over.
                parent.trigger_user_event((void*)this,drawable::next_free_user_event_number());
                return false;
            }

            return is_mouse_over_;
        }

    // ----------------------------------------------------------------------------------------

        void mouse_over_event::
        on_user_event (
            int num
        )
        {
            if (is_mouse_over_ && num == drawable::next_free_user_event_number())
            {
                is_mouse_over_ = false;
                on_mouse_not_over();
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
        // button_action object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        button_action::~button_action() {}

    // ----------------------------------------------------------------------------------------

        void button_action::
        on_mouse_down (
            unsigned long btn,
            unsigned long ,
            long x,
            long y,
            bool
        )
        {
            if (enabled && !hidden && btn == base_window::LEFT && rect.contains(x,y))
            {
                is_depressed_ = true;
                seen_click = true;
                parent.invalidate_rectangle(rect);
                on_button_down();
            }
        }

    // ----------------------------------------------------------------------------------------

        void button_action::
        on_mouse_not_over (
        )
        {
            if (is_depressed_)
            {
                is_depressed_ = false;
                parent.invalidate_rectangle(rect);
                on_button_up(false);
            }
        }

    // ----------------------------------------------------------------------------------------

        void button_action::
        on_mouse_move (
            unsigned long state,
            long x,
            long y
        )
        {
            // forward event to the parent class so it can do it's thing as well as us
            mouse_over_event::on_mouse_move(state,x,y);

            if (enabled == false || hidden == true)
                return;

            if ((state & base_window::LEFT) == 0)
            {
                seen_click = false;
                if (is_depressed_)
                {
                    is_depressed_ = false;
                    parent.invalidate_rectangle(rect);
                    on_button_up(false);
                }

                // the left button isn't down so we don't care about anything else
                return;
            }

            if (rect.contains(x,y) == false)
            {
                if (is_depressed_)
                {
                    is_depressed_ = false;
                    parent.invalidate_rectangle(rect);
                    on_button_up(false);
                }
            }
            else if (is_depressed_ == false && seen_click)
            {
                is_depressed_ = true;
                parent.invalidate_rectangle(rect);
                on_button_down();
            }
        }

    // ----------------------------------------------------------------------------------------

        void button_action::
        on_mouse_up (
            unsigned long btn,
            unsigned long,
            long x,
            long y
        )
        {
            if (enabled && !hidden && btn == base_window::LEFT)
            {
                if (is_depressed_)
                {
                    is_depressed_ = false;
                    parent.invalidate_rectangle(rect);

                    if (rect.contains(x,y))
                    {
                        on_button_up(true);
                    }
                    else
                    {
                        on_button_up(false);
                    }
                }
                else if (seen_click && rect.contains(x,y))
                {
                    // this case here covers the unlikly event that you click on a button,
                    // move the mouse off the button and then move it back very quickly and
                    // release the mouse button.   It is possible that this mouse up event
                    // will occur before any mouse move event so you might not have set
                    // that the button is depressed yet.

                    // So we should say that this triggers an on_button_down() event and
                    // then an on_button_up(true) event.

                    parent.invalidate_rectangle(rect);

                    on_button_down();
                    on_button_up(true);
                }

                seen_click = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        bool button_action::
        is_depressed (
        ) const
        {
            // check if the mouse is still really over this button
            if (enabled && !hidden && is_depressed_ && rect.contains(lastx,lasty) == false)
            {
                // trigger a user event to call on_button_up() and repaint this object.
                // we must do this in another event because someone might call is_depressed()
                // from draw() and you don't want this function to end up calling
                // parent.invalidate_rectangle().  It would lead to draw() being called over
                // and over.
                parent.trigger_user_event((void*)this,mouse_over_event::next_free_user_event_number());
                return false;
            }

            return is_depressed_;
        }

    // ----------------------------------------------------------------------------------------

        void button_action::
        on_user_event (
            int num
        )
        {
            // forward event to the parent class so it can do it's thing as well as us
            mouse_over_event::on_user_event(num);

            if (is_depressed_ && num == mouse_over_event::next_free_user_event_number())
            {
                is_depressed_ = false;
                parent.invalidate_rectangle(rect);
                on_button_up(false);
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
        // scroll_bar object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        scroll_bar::
        scroll_bar(
            drawable_window& w,
            bar_orientation orientation
        ) :
            drawable(w),
            b1(w),
            b2(w),
            slider(w,*this,&scroll_bar::on_slider_drag),
            ori(orientation),
            top_filler(w,*this,&scroll_bar::top_filler_down,&scroll_bar::top_filler_up),
            bottom_filler(w,*this,&scroll_bar::bottom_filler_down,&scroll_bar::bottom_filler_up),
            pos(0),
            max_pos(0),
            js(10),
            b1_timer(*this,&scroll_bar::b1_down_t),
            b2_timer(*this,&scroll_bar::b2_down_t),
            top_filler_timer(*this,&scroll_bar::top_filler_down_t),
            bottom_filler_timer(*this,&scroll_bar::bottom_filler_down_t)
        {
            set_style(scroll_bar_style_default());

            // don't show the slider when there is no place it can move.
            slider.hide();

            set_length(100);

            b1.set_button_down_handler(*this,&scroll_bar::b1_down);
            b2.set_button_down_handler(*this,&scroll_bar::b2_down);

            b1.set_button_up_handler(*this,&scroll_bar::b1_up);
            b2.set_button_up_handler(*this,&scroll_bar::b2_up);
            b1.disable();
            b2.disable();
            enable_events();
        }

    // ----------------------------------------------------------------------------------------

        scroll_bar::
        ~scroll_bar(
        )
        {
            disable_events();
            parent.invalidate_rectangle(rect);
            // wait for all the timers to be stopped
            b1_timer.stop_and_wait();
            b2_timer.stop_and_wait();
            top_filler_timer.stop_and_wait();
            bottom_filler_timer.stop_and_wait();
        }

    // ----------------------------------------------------------------------------------------

        scroll_bar::bar_orientation scroll_bar::
        orientation (
        ) const
        {
            auto_mutex M(m);
            return ori;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        set_length (
            unsigned long length
        )
        {
            auto_mutex M(m);
            // make the min length be at least 1
            if (length == 0)
            {
                length = 1;
            }

            parent.invalidate_rectangle(rect);

            if (ori == HORIZONTAL)
            {
                rect.set_right(rect.left() + length - 1);
                rect.set_bottom(rect.top() + style->get_width() - 1);

                const long btn_size = style->get_button_length(rect.width(), max_pos);

                b1.set_size(btn_size,style->get_width());
                b2.set_size(btn_size,style->get_width());

                slider.set_size(get_slider_size(),style->get_width());
            }
            else
            {
                rect.set_right(rect.left() + style->get_width() - 1);
                rect.set_bottom(rect.top() + length - 1);

                const long btn_size = style->get_button_length(rect.height(), max_pos);

                b1.set_size(style->get_width(),btn_size);
                b2.set_size(style->get_width(),btn_size);

                slider.set_size(style->get_width(),get_slider_size());
            }

            // call this to put everything is in the right spot.
            set_pos (rect.left(),rect.top());

            if ((b2.get_rect().top() - b1.get_rect().bottom() - 1 <= 8 && ori == VERTICAL) ||
                (b2.get_rect().left() - b1.get_rect().right() - 1 <= 8 && ori == HORIZONTAL) ||
                max_pos == 0)
            {
                hide_slider();
            }
            else if (enabled && !hidden)
            {
                show_slider();
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        set_pos (
            long x,
            long y
        )
        {
            auto_mutex M(m);
            drawable::set_pos(x,y);

            b1.set_pos(rect.left(),rect.top());
            if (ori == HORIZONTAL)
            {
                // make the b2 button appear at the end of the scroll_bar
                b2.set_pos(rect.right()-b2.get_rect().width() + 1,rect.top());

                if (max_pos != 0)
                {
                    double range = b2.get_rect().left() - b1.get_rect().right() - slider.get_rect().width() - 1;
                    double slider_pos = pos;
                    slider_pos /= max_pos;
                    slider_pos *= range;
                    slider.set_pos(
                        static_cast<long>(slider_pos)+rect.left() + b1.get_rect().width(),
                        rect.top()
                        );

                    // move the draggable area for the slider to the new location
                    rectangle area = rect;
                    area.set_left(area.left() + style->get_width());
                    area.set_right(area.right() - style->get_width());
                    slider.set_draggable_area(area);

                }

            }
            else
            {
                // make the b2 button appear at the end of the scroll_bar
                b2.set_pos(rect.left(), rect.bottom() - b2.get_rect().height() + 1);

                if (max_pos != 0)
                {
                    double range = b2.get_rect().top() - b1.get_rect().bottom() - slider.get_rect().height() - 1;
                    double slider_pos = pos;
                    slider_pos /= max_pos;
                    slider_pos *= range;
                    slider.set_pos(
                        rect.left(),
                        static_cast<long>(slider_pos) + rect.top() + b1.get_rect().height()
                        );

                    // move the draggable area for the slider to the new location
                    rectangle area = rect;
                    area.set_top(area.top() + style->get_width());
                    area.set_bottom(area.bottom() - style->get_width());
                    slider.set_draggable_area(area);
                }
            }

            adjust_fillers();
        }

    // ----------------------------------------------------------------------------------------

        unsigned long scroll_bar::
        get_slider_size (
        ) const
        {
            if (ori == HORIZONTAL)
                return style->get_slider_length(rect.width(),max_pos);
            else
                return style->get_slider_length(rect.height(),max_pos);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        adjust_fillers (
        )
        {
            rectangle top(rect), bottom(rect);

            if (ori == HORIZONTAL)
            {
                if (slider.is_hidden())
                {
                    top.set_left(b1.get_rect().right()+1);
                    top.set_right(b2.get_rect().left()-1);
                    bottom.set_left(1);
                    bottom.set_right(-1);
                }
                else
                {
                    top.set_left(b1.get_rect().right()+1);
                    top.set_right(slider.get_rect().left()-1);
                    bottom.set_left(slider.get_rect().right()+1);
                    bottom.set_right(b2.get_rect().left()-1);
                }
            }
            else
            {
                if (slider.is_hidden())
                {
                    top.set_top(b1.get_rect().bottom()+1);
                    top.set_bottom(b2.get_rect().top()-1);
                    bottom.set_top(1);
                    bottom.set_bottom(-1);
                }
                else
                {
                    top.set_top(b1.get_rect().bottom()+1);
                    top.set_bottom(slider.get_rect().top()-1);
                    bottom.set_top(slider.get_rect().bottom()+1);
                    bottom.set_bottom(b2.get_rect().top()-1);
                }
            }

            top_filler.rect = top;
            bottom_filler.rect = bottom;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        hide_slider (
        )
        {
            rectangle top(rect), bottom(rect);
            slider.hide();
            top_filler.disable();
            bottom_filler.disable();
            bottom_filler.hide();
            if (ori == HORIZONTAL)
            {
                top.set_left(b1.get_rect().right()+1);
                top.set_right(b2.get_rect().left()-1);
            }
            else
            {
                top.set_top(b1.get_rect().bottom()+1);
                top.set_bottom(b2.get_rect().top()-1);
            }
            top_filler.rect = top;
            bottom_filler.rect = bottom;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        show_slider (
        )
        {
            if ((b2.get_rect().top() - b1.get_rect().bottom() - 1 <= 8 && ori == VERTICAL) ||
                (b2.get_rect().left() - b1.get_rect().right() - 1 <= 8 && ori == HORIZONTAL) ||
                max_pos == 0)
                return;

            rectangle top(rect), bottom(rect);
            slider.show();
            top_filler.enable();
            bottom_filler.enable();
            bottom_filler.show();
            if (ori == HORIZONTAL)
            {
                top.set_left(b1.get_rect().right()+1);
                top.set_right(slider.get_rect().left()-1);
                bottom.set_left(slider.get_rect().right()+1);
                bottom.set_right(b2.get_rect().left()-1);
            }
            else
            {
                top.set_top(b1.get_rect().bottom()+1);
                top.set_bottom(slider.get_rect().top()-1);
                bottom.set_top(slider.get_rect().bottom()+1);
                bottom.set_bottom(b2.get_rect().top()-1);
            }
            top_filler.rect = top;
            bottom_filler.rect = bottom;
        }

    // ----------------------------------------------------------------------------------------

        long scroll_bar::
        max_slider_pos (
        ) const
        {
            auto_mutex M(m);
            return max_pos;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        set_max_slider_pos (
            long mpos
        )
        {
            auto_mutex M(m);
            max_pos = mpos;
            if (pos > mpos)
                pos = mpos;

            if (ori == HORIZONTAL)
                set_length(rect.width());
            else
                set_length(rect.height());

            if (mpos != 0 && enabled)
            {
                b1.enable();
                b2.enable();
            }
            else
            {
                b1.disable();
                b2.disable();
            }

        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        set_slider_pos (
            long pos
        )
        {
            auto_mutex M(m);
            if (pos < 0)
                pos = 0;
            if (pos > max_pos)
                pos = max_pos;

            this->pos = pos;

            // move the slider object to its new position
            set_pos(rect.left(),rect.top());
        }

    // ----------------------------------------------------------------------------------------

        long scroll_bar::
        slider_pos (
        ) const
        {
            auto_mutex M(m);
            return pos;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        on_slider_drag (
        )
        {
            if (ori == HORIZONTAL)
            {
                double slider_pos = slider.get_rect().left() - b1.get_rect().right() - 1;
                double range = b2.get_rect().left() - b1.get_rect().right() - slider.get_rect().width() - 1;
                slider_pos /= range;
                slider_pos *= max_pos;
                pos = static_cast<unsigned long>(slider_pos);
            }
            else
            {
                double slider_pos = slider.get_rect().top() - b1.get_rect().bottom() - 1;
                double range = b2.get_rect().top() - b1.get_rect().bottom() - slider.get_rect().height() - 1;
                slider_pos /= range;
                slider_pos *= max_pos;
                pos = static_cast<unsigned long>(slider_pos);
            }

            adjust_fillers();

            if (scroll_handler.is_set())
                scroll_handler();
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        draw (
            const canvas&
        ) const
        {
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b1_down (
        )
        {
            if (pos != 0)
            {
                set_slider_pos(pos-1);
                if (scroll_handler.is_set())
                    scroll_handler();

                if (b1_timer.delay_time() == 1000)
                    b1_timer.set_delay_time(500);
                else
                    b1_timer.set_delay_time(50);
                b1_timer.start();
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b1_up (
            bool
        )
        {
            b1_timer.stop();
            b1_timer.set_delay_time(1000);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b2_down (
        )
        {
            if (pos != max_pos)
            {
                set_slider_pos(pos+1);
                if (scroll_handler.is_set())
                    scroll_handler();

                if (b2_timer.delay_time() == 1000)
                    b2_timer.set_delay_time(500);
                else
                    b2_timer.set_delay_time(50);
                b2_timer.start();
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b2_up (
            bool
        )
        {
            b2_timer.stop();
            b2_timer.set_delay_time(1000);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        top_filler_down (
        )
        {
            // ignore this if the mouse is now outside this object.  This could happen
            // since the timers are also calling this function.
            if (top_filler.rect.contains(lastx,lasty) == false)
            {
                top_filler_up(false);
                return;
            }

            if (pos != 0)
            {
                if (pos < js)
                {
                    // if there is less than jump_size() space left then jump the remaining
                    // amount.
                    delayed_set_slider_pos(0);
                }
                else
                {
                    delayed_set_slider_pos(pos-js);
                }

                if (top_filler_timer.delay_time() == 1000)
                    top_filler_timer.set_delay_time(500);
                else
                    top_filler_timer.set_delay_time(50);
                top_filler_timer.start();
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        top_filler_up (
            bool
        )
        {
            top_filler_timer.stop();
            top_filler_timer.set_delay_time(1000);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        bottom_filler_down (
        )
        {
            // ignore this if the mouse is now outside this object.  This could happen
            // since the timers are also calling this function.
            if (bottom_filler.rect.contains(lastx,lasty) == false)
            {
                bottom_filler_up(false);
                return;
            }

            if (pos != max_pos)
            {
                if (max_pos - pos < js)
                {
                    // if there is less than jump_size() space left then jump the remaining
                    // amount.
                    delayed_set_slider_pos(max_pos);
                }
                else
                {
                    delayed_set_slider_pos(pos+js);
                }

                if (bottom_filler_timer.delay_time() == 1000)
                    bottom_filler_timer.set_delay_time(500);
                else
                    bottom_filler_timer.set_delay_time(50);
                bottom_filler_timer.start();
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        bottom_filler_up (
            bool
        )
        {
            bottom_filler_timer.stop();
            bottom_filler_timer.set_delay_time(1000);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        set_jump_size (
            long js_
        )
        {
            auto_mutex M(m);
            if (js_ < 1)
                js = 1;
            else
                js = js_;
        }

    // ----------------------------------------------------------------------------------------

        long scroll_bar::
        jump_size (
        ) const
        {
            auto_mutex M(m);
            return js;
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        on_user_event (
            int i
        )
        {
            switch (i)
            {
                case 0:
                    b1_down();
                    break;
                case 1:
                    b2_down();
                    break;
                case 2:
                    top_filler_down();
                    break;
                case 3:
                    bottom_filler_down();
                    break;
                case 4:
                    // if the position we are supposed to switch the slider too isn't
                    // already set
                    if (delayed_pos != pos)
                    {
                        set_slider_pos(delayed_pos);
                        if (scroll_handler.is_set())
                            scroll_handler();
                    }
                    break;
                default:
                    break;
            }
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        delayed_set_slider_pos (
            unsigned long dpos
        )
        {
            delayed_pos = dpos;
            parent.trigger_user_event(this,4);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b1_down_t (
        )
        {
            parent.trigger_user_event(this,0);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        b2_down_t (
        )
        {
            parent.trigger_user_event(this,1);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        top_filler_down_t (
        )
        {
            parent.trigger_user_event(this,2);
        }

    // ----------------------------------------------------------------------------------------

        void scroll_bar::
        bottom_filler_down_t (
        )
        {
            parent.trigger_user_event(this,3);
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    //                  widget_group object methods
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        void widget_group::
        empty (
        )
        {
            auto_mutex M(m);
            widgets.clear();
            wg_widgets.clear();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        add (
            drawable& widget,
            unsigned long x,
            unsigned long y
        )
        {
            auto_mutex M(m);
            drawable* w = &widget;
            relpos rp;
            rp.x = x;
            rp.y = y;
            if (widgets.is_in_domain(w))
            {
                widgets[w].x = x;
                widgets[w].y = y;
            }
            else
            {
                widgets.add(w,rp);
            }
            if (is_hidden())
                widget.hide();
            else
                widget.show();

            if (is_enabled())
                widget.enable();
            else
                widget.disable();

            widget.set_z_order(z_order());
            widget.set_pos(x+rect.left(),y+rect.top());
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        add (
            widget_group& widget,
            unsigned long x,
            unsigned long y
        )
        {
            auto_mutex M(m);
            drawable& w = widget;
            add(w, x, y);

            widget_group* wg = &widget;
            wg_widgets.add(wg);
        }

    // ----------------------------------------------------------------------------------------

        bool widget_group::
        is_member (
            const drawable& widget
        ) const
        {
            auto_mutex M(m);
            drawable* w = const_cast<drawable*>(&widget);
            return widgets.is_in_domain(w);
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        remove (
            const drawable& widget
        )
        {
            auto_mutex M(m);
            drawable* w = const_cast<drawable*>(&widget);
            if (widgets.is_in_domain(w))
            {
                widgets.destroy(w);

                // check if we also have an entry in the wg_widgets set and if
                // so then remove that too
                widget_group* wg = reinterpret_cast<widget_group*>(w);
                if (wg_widgets.is_member(wg))
                {
                    wg_widgets.destroy(wg);
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        size_t widget_group::
        size (
        ) const
        {
            auto_mutex M(m);
            return widgets.size();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        set_pos (
            long x,
            long y
        )
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
            {
                const unsigned long rx = widgets.element().value().x;
                const unsigned long ry = widgets.element().value().y;
                widgets.element().key()->set_pos(x+rx,y+ry);
            }
            drawable::set_pos(x,y);
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        set_z_order (
            long order
        )
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
                widgets.element().key()->set_z_order(order);
            drawable::set_z_order(order);
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        show (
        )
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
                widgets.element().key()->show();
            drawable::show();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        hide (
        )
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
                widgets.element().key()->hide();
            drawable::hide();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        enable (
        )
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
                widgets.element().key()->enable();
            drawable::enable();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        disable ()
        {
            auto_mutex M(m);
            widgets.reset();
            while (widgets.move_next())
                widgets.element().key()->disable();
            drawable::disable();
        }

    // ----------------------------------------------------------------------------------------

        void widget_group::
        fit_to_contents (
        )
        {
            auto_mutex M(m);

            // call fit_to_contents on all the widget_groups we contain
            wg_widgets.reset();
            while (wg_widgets.move_next())
                wg_widgets.element()->fit_to_contents();

            // now accumulate a rectangle that contains everything in this widget_group
            rectangle r;
            widgets.reset();
            while (widgets.move_next())
                r = r + widgets.element().key()->get_rect();

            if (r.is_empty())
            {
                // make sure it is still empty after we set it at the correct position
                r.set_right(rect.left()-1);
                r.set_bottom(rect.top()-1);
            }

            r.set_left(rect.left());
            r.set_top(rect.top());
            rect = r;
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    //                class popup_menu
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        popup_menu::
        popup_menu (
        ) :
            base_window(false,true),
            pad(2),
            item_pad(3),
            cur_rect(pad,pad,pad-1,pad-1),
            left_width(0),
            middle_width(0),
            selected_item(0),
            submenu_open(false)
        {
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        enable_menu_item (
            unsigned long idx
        )
        {
            DLIB_ASSERT ( idx < size() ,
                          "\tvoid popup_menu::enable_menu_item()"
                          << "\n\tidx:    " << idx
                          << "\n\tsize(): " << size()
            );
            auto_mutex M(wm);
            item_enabled[idx] = true;
            invalidate_rectangle(cur_rect);
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        disable_menu_item (
            unsigned long idx
        )
        {
            DLIB_ASSERT ( idx < size() ,
                          "\tvoid popup_menu::enable_menu_item()"
                          << "\n\tidx:    " << idx
                          << "\n\tsize(): " << size()
            );
            auto_mutex M(wm);
            item_enabled[idx] = false;
            invalidate_rectangle(cur_rect);
        }

    // ----------------------------------------------------------------------------------------

        size_t popup_menu::
        size (
        ) const
        {
            auto_mutex M(wm);
            return items.size();
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        clear (
        )
        {
            auto_mutex M(wm);
            hide();
            cur_rect = rectangle(pad,pad,pad-1,pad-1);
            win_rect = rectangle();
            left_width = 0;
            middle_width = 0;
            items.clear();
            item_enabled.clear();
            left_rects.clear();
            middle_rects.clear();
            right_rects.clear();
            line_rects.clear();
            submenus.clear();
            selected_item = 0;
            submenu_open = false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        show (
        )
        {
            auto_mutex M(wm);
            selected_item = submenus.size();
            base_window::show();
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        hide (
        )
        {
            auto_mutex M(wm);
            // hide ourselves
            close_submenu();
            selected_item = submenus.size();
            base_window::hide();
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        select_first_item (
        )
        {
            auto_mutex M(wm);
            close_submenu();
            selected_item = items.size();
            for (unsigned long i = 0; i < items.size(); ++i)
            {
                if ((items[i]->has_click_event() || submenus[i]) && item_enabled[i])
                {
                    selected_item = i;
                    break;
                }
            }
            invalidate_rectangle(cur_rect);
        }

    // ----------------------------------------------------------------------------------------

        bool popup_menu::
        forwarded_on_keydown (
            unsigned long key,
            bool is_printable,
            unsigned long state
        )
        {
            auto_mutex M(wm);
            // do nothing if this popup menu is empty
            if (items.size() == 0)
                return false;

            // check if the selected item is a submenu
            if (selected_item != submenus.size() && submenus[selected_item] != 0 && submenu_open)
            {
                // send the key to the submenu and return if that menu used the key
                if (submenus[selected_item]->forwarded_on_keydown(key,is_printable,state) == true)
                    return true;
            }

            if (key == KEY_UP)
            {
                for (unsigned long i = 0; i < items.size(); ++i)
                {
                    selected_item = (selected_item + items.size() - 1)%items.size();
                    // only stop looking if this one is enabled and has a click event or is a submenu
                    if (item_enabled[selected_item] && (items[selected_item]->has_click_event() || submenus[selected_item]) )
                        break;
                }
                invalidate_rectangle(cur_rect);
                return true;
            }
            else if (key == KEY_DOWN)
            {
                for (unsigned long i = 0; i < items.size(); ++i)
                {
                    selected_item = (selected_item + 1)%items.size();
                    // only stop looking if this one is enabled and has a click event or is a submenu
                    if (item_enabled[selected_item] && (items[selected_item]->has_click_event() || submenus[selected_item]))
                        break;
                }
                invalidate_rectangle(cur_rect);
                return true;
            }
            else if (key == KEY_RIGHT && submenu_open == false && display_selected_submenu())
            {
                submenus[selected_item]->select_first_item();
                return true;
            }
            else if (key == KEY_LEFT && selected_item != submenus.size() &&
                     submenus[selected_item] != 0 && submenu_open)
            {
                close_submenu();
                return true;
            }
            else if (key == '\n')
            {
                if (selected_item != submenus.size() && (items[selected_item]->has_click_event() || submenus[selected_item]))
                {
                    const long idx = selected_item;
                    // only hide this popup window if this isn't a submenu
                    if (submenus[idx] == 0)
                    {
                        hide();
                        hide_handlers.reset();
                        while (hide_handlers.move_next())
                            hide_handlers.element()();
                    }
                    else
                    {
                        display_selected_submenu();
                        submenus[idx]->select_first_item();
                    }
                    items[idx]->on_click();
                    return true;
                }
            }
            else if (is_printable)
            {
                // check if there is a hotkey for this key
                for (unsigned long i = 0; i < items.size(); ++i)
                {
                    if (std::tolower(key) == std::tolower(items[i]->get_hot_key()) &&
                        (items[i]->has_click_event() || submenus[i]) && item_enabled[i] )
                    {
                        // only hide this popup window if this isn't a submenu
                        if (submenus[i] == 0)
                        {
                            hide();
                            hide_handlers.reset();
                            while (hide_handlers.move_next())
                                hide_handlers.element()();
                        }
                        else
                        {
                            if (selected_item != items.size())
                                invalidate_rectangle(line_rects[selected_item]);

                            selected_item = i;
                            display_selected_submenu();
                            invalidate_rectangle(line_rects[i]);
                            submenus[i]->select_first_item();
                        }
                        items[i]->on_click();
                    }
                }

                // always say we use a printable key for hotkeys
                return true;
            }

            return false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        on_submenu_hide (
        )
        {
            hide();
            hide_handlers.reset();
            while (hide_handlers.move_next())
                hide_handlers.element()();
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        on_window_resized(
        )
        {
            invalidate_rectangle(win_rect);
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        on_mouse_up (
            unsigned long btn,
            unsigned long,
            long x,
            long y
        )
        {
            if (cur_rect.contains(x,y) && btn == LEFT)
            {
                // figure out which item this was on
                for (unsigned long i = 0; i < items.size(); ++i)
                {
                    if (line_rects[i].contains(x,y) && item_enabled[i] && items[i]->has_click_event())
                    {
                        // only hide this popup window if this isn't a submenu
                        if (submenus[i] == 0)
                        {
                            hide();
                            hide_handlers.reset();
                            while (hide_handlers.move_next())
                                hide_handlers.element()();
                        }
                        items[i]->on_click();
                        break;
                    }
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        on_mouse_move (
            unsigned long ,
            long x,
            long y
        )
        {
            if (cur_rect.contains(x,y))
            {
                // check if the mouse is still in the same rect it was in last time
                rectangle last_rect;
                if (selected_item != submenus.size())
                {
                    last_rect = line_rects[selected_item];
                }

                // if the mouse isn't in the same rectangle any more
                if (last_rect.contains(x,y) == false)
                {
                    if (selected_item != submenus.size())
                    {
                        invalidate_rectangle(last_rect);
                        close_submenu();
                        selected_item = submenus.size();
                    }

                    // figure out if we should redraw any menu items
                    for (unsigned long i = 0; i < items.size(); ++i)
                    {
                        if (items[i]->has_click_event() || submenus[i])
                        {
                            if (line_rects[i].contains(x,y))
                            {
                                selected_item = i;
                                break;
                            }
                        }
                    }

                    // if we found a rectangle that contains the mouse then
                    // tell it to redraw itself
                    if (selected_item != submenus.size())
                    {
                        display_selected_submenu();
                        invalidate_rectangle(line_rects[selected_item]);
                    }
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        close_submenu (
        )
        {
            if (selected_item != submenus.size() && submenus[selected_item] && submenu_open)
            {
                submenus[selected_item]->hide();
                submenu_open = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        bool popup_menu::
        display_selected_submenu (
        )
        {
            // show the submenu if one exists
            if (selected_item != submenus.size() && submenus[selected_item])
            {
                long wx, wy;
                get_pos(wx,wy);
                wx += line_rects[selected_item].right();
                wy += line_rects[selected_item].top();
                submenus[selected_item]->set_pos(wx+1,wy-2);
                submenus[selected_item]->show();
                submenu_open = true;
                return true;
            }
            return false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        on_mouse_leave (
        )
        {
            if (selected_item != submenus.size())
            {
                // only unhighlight a menu item if it isn't a submenu item
                if (submenus[selected_item] == 0)
                {
                    invalidate_rectangle(line_rects[selected_item]);
                    selected_item = submenus.size();
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu::
        paint (
            const canvas& c
        )
        {
            c.fill(200,200,200);
            draw_rectangle(c, win_rect);
            for (unsigned long i = 0; i < items.size(); ++i)
            {
                bool is_selected = false;
                if (selected_item != submenus.size() && i == selected_item &&
                    item_enabled[i])
                    is_selected = true;

                items[i]->draw_background(c,line_rects[i], item_enabled[i], is_selected);
                items[i]->draw_left(c,left_rects[i], item_enabled[i], is_selected);
                items[i]->draw_middle(c,middle_rects[i], item_enabled[i], is_selected);
                items[i]->draw_right(c,right_rects[i], item_enabled[i], is_selected);
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    //              class zoomable_region
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        zoomable_region::
        zoomable_region (
            drawable_window& w,
            unsigned long events
        ) :
            drawable(w,MOUSE_CLICK | MOUSE_WHEEL | MOUSE_MOVE | events),
            min_scale(0.15),
            max_scale(1.0),
            zoom_increment_(0.90),
            vsb(w, scroll_bar::VERTICAL),
            hsb(w, scroll_bar::HORIZONTAL)
        {
            scale = 1;
            mouse_drag_screen = false;
            style.reset(new scrollable_region_style_default());

            hsb.set_scroll_handler(*this,&zoomable_region::on_h_scroll);
            vsb.set_scroll_handler(*this,&zoomable_region::on_v_scroll);
        }

    // ----------------------------------------------------------------------------------------

        zoomable_region::
        ~zoomable_region()
        {
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_pos (
            long x,
            long y
        )
        {
            auto_mutex M(m);
            drawable::set_pos(x,y);
            const long border_size = style->get_border_size();
            vsb.set_pos(rect.right()-border_size+1-vsb.width(),rect.top()+border_size);
            hsb.set_pos(rect.left()+border_size,rect.bottom()-border_size+1-hsb.height());

            display_rect_ = rectangle(rect.left()+border_size,
                                      rect.top()+border_size,
                                      rect.right()-border_size-vsb.width(),
                                      rect.bottom()-border_size-hsb.height());

        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_zoom_increment (
            double zi
        )
        {
            DLIB_ASSERT(0.0 < zi && zi < 1.0,
                        "\tvoid zoomable_region::set_zoom_increment(zi)"
                        << "\n\t the zoom increment must be between 0 and 1"
                        << "\n\t zi:   " << zi
                        << "\n\t this: " << this
            );

            auto_mutex M(m);
            zoom_increment_ = zi;
        }

    // ----------------------------------------------------------------------------------------

        double zoomable_region::
        zoom_increment (
        ) const
        {
            auto_mutex M(m);
            return zoom_increment_;
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_max_zoom_scale (
            double ms
        )
        {
            DLIB_ASSERT(ms > 0,
                        "\tvoid zoomable_region::set_max_zoom_scale(ms)"
                        << "\n\t the max zoom scale must be greater than 0"
                        << "\n\t ms:   " << ms
                        << "\n\t this: " << this
            );

            auto_mutex M(m);
            max_scale = ms;
            if (scale > ms)
            {
                scale = max_scale;
                lr_point = gui_to_graph_space(point(display_rect_.right(),display_rect_.bottom()));
                redraw_graph();
            }
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_min_zoom_scale (
            double ms
        )
        {
            DLIB_ASSERT(ms > 0,
                        "\tvoid zoomable_region::set_min_zoom_scale(ms)"
                        << "\n\t the min zoom scale must be greater than 0"
                        << "\n\t ms:   " << ms
                        << "\n\t this: " << this
            );

            auto_mutex M(m);
            min_scale = ms;

            if (scale < ms)
            {
                scale = min_scale;
            }

            // just call set_size so that everything gets redrawn right
            set_size(rect.width(), rect.height());
        }

    // ----------------------------------------------------------------------------------------

        double zoomable_region::
        min_zoom_scale (
        ) const
        {
            auto_mutex M(m);
            return min_scale;
        }

    // ----------------------------------------------------------------------------------------

        double zoomable_region::
        max_zoom_scale (
        ) const
        {
            auto_mutex M(m);
            return max_scale;
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_size (
            unsigned long width,
            unsigned long height
        )
        {
            auto_mutex M(m);
            rectangle old(rect);
            const long border_size = style->get_border_size();
            rect = resize_rect(rect,width,height);
            vsb.set_pos(rect.right()-border_size+1-vsb.width(),  rect.top()+border_size);
            hsb.set_pos(rect.left()+border_size,  rect.bottom()-border_size+1-hsb.height());

            display_rect_ = rectangle(rect.left()+border_size,
                                      rect.top()+border_size,
                                      rect.right()-border_size-vsb.width(),
                                      rect.bottom()-border_size-hsb.height());
            vsb.set_length(display_rect_.height());
            hsb.set_length(display_rect_.width());
            parent.invalidate_rectangle(rect+old);

            const double old_scale = scale;
            const vector<double,2> old_gr_orig(gr_orig);
            scale = min_scale;
            gr_orig = vector<double,2>(0,0);
            lr_point = gui_to_graph_space(point(display_rect_.right(),display_rect_.bottom()));
            scale = old_scale;

            // call adjust_origin() so that the scroll bars get their max slider positions
            // setup right
            const point rect_corner(display_rect_.left(), display_rect_.top());
            adjust_origin(rect_corner, old_gr_orig);
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        show (
        )
        {
            auto_mutex M(m);
            drawable::show();
            hsb.show();
            vsb.show();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        hide (
        )
        {
            auto_mutex M(m);
            drawable::hide();
            hsb.hide();
            vsb.hide();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        enable (
        )
        {
            auto_mutex M(m);
            drawable::enable();
            hsb.enable();
            vsb.enable();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        disable (
        )
        {
            auto_mutex M(m);
            drawable::disable();
            hsb.disable();
            vsb.disable();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_z_order (
            long order
        )
        {
            auto_mutex M(m);
            drawable::set_z_order(order);
            hsb.set_z_order(order);
            vsb.set_z_order(order);
        }

    // ----------------------------------------------------------------------------------------

        point zoomable_region::
        graph_to_gui_space (
            const vector<double,2>& p
        ) const
        {
            const point rect_corner(display_rect_.left(), display_rect_.top());
            return (p - gr_orig)*scale + rect_corner;
        }

    // ----------------------------------------------------------------------------------------

        vector<double,2> zoomable_region::
        gui_to_graph_space (
            const point& p
        ) const
        {
            const point rect_corner(display_rect_.left(), display_rect_.top());
            return (p - rect_corner)/scale + gr_orig;
        }

    // ----------------------------------------------------------------------------------------

        point zoomable_region::
        max_graph_point (
        ) const
        {
            return lr_point;
        }

    // ----------------------------------------------------------------------------------------

        rectangle zoomable_region::
        display_rect (
        ) const
        {
            return display_rect_;
        }

    // ----------------------------------------------------------------------------------------

        double zoomable_region::
        zoom_scale (
        ) const
        {
            return scale;
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        set_zoom_scale (
            double new_scale
        )
        {
            // if new_scale isn't in the right range then put it back in range before we do the
            // rest of this function
            if (!(min_scale <= new_scale && new_scale <= max_scale))
            {
                if (new_scale > max_scale)
                    new_scale = max_scale;
                else
                    new_scale = min_scale;
            }

            // find the point in the center of the graph area
            point center((display_rect_.left()+display_rect_.right())/2,  (display_rect_.top()+display_rect_.bottom())/2);
            point graph_p(gui_to_graph_space(center));
            scale = new_scale;
            adjust_origin(center, graph_p);
            redraw_graph();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        center_display_at_graph_point (
            const vector<double,2>& p
        )
        {
            // find the point in the center of the graph area
            point center((display_rect_.left()+display_rect_.right())/2,  (display_rect_.top()+display_rect_.bottom())/2);
            adjust_origin(center, p);
            redraw_graph();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_wheel_down (
            unsigned long
        )
        {
            // zoom out
            if (enabled && !hidden && scale > min_scale && display_rect_.contains(lastx,lasty))
            {
                point gui_p(lastx,lasty);
                point graph_p(gui_to_graph_space(gui_p));
                const double old_scale = scale;
                scale *= zoom_increment_;
                if (scale < min_scale)
                    scale = min_scale;
                redraw_graph();
                adjust_origin(gui_p, graph_p);

                if (scale != old_scale)
                    on_view_changed();
            }
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_wheel_up (
            unsigned long
        )
        {
            // zoom in
            if (enabled && !hidden && scale < max_scale  && display_rect_.contains(lastx,lasty))
            {
                point gui_p(lastx,lasty);
                point graph_p(gui_to_graph_space(gui_p));
                const double old_scale = scale;
                scale /= zoom_increment_;
                if (scale > max_scale)
                    scale = max_scale;
                redraw_graph();
                adjust_origin(gui_p, graph_p);

                if (scale != old_scale)
                    on_view_changed();
            }
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_mouse_move (
            unsigned long state,
            long x,
            long y
        )
        {
            if (enabled && !hidden && mouse_drag_screen)
            {
                adjust_origin(point(x,y), drag_screen_point);
                redraw_graph();
                on_view_changed();
            }

            // check if the mouse isn't being dragged anymore
            if ((state & base_window::LEFT) == 0)
            {
                mouse_drag_screen = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_mouse_up (
            unsigned long ,
            unsigned long ,
            long ,
            long
        )
        {
            mouse_drag_screen = false;
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_mouse_down (
            unsigned long btn,
            unsigned long ,
            long x,
            long y,
            bool
        )
        {
            if (enabled && !hidden && display_rect_.contains(x,y) && btn == base_window::LEFT)
            {
                mouse_drag_screen = true;
                drag_screen_point = gui_to_graph_space(point(x,y));
            }
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        draw (
            const canvas& c
        ) const
        {
            style->draw_scrollable_region_border(c, rect, enabled);
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_h_scroll (
        )
        {
            gr_orig.x() = hsb.slider_pos();
            redraw_graph();

            on_view_changed();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        on_v_scroll (
        )
        {
            gr_orig.y() = vsb.slider_pos();
            redraw_graph();

            on_view_changed();
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        redraw_graph (
        )
        {
            parent.invalidate_rectangle(display_rect_);
        }

    // ----------------------------------------------------------------------------------------

        void zoomable_region::
        adjust_origin (
            const point& gui_p,
            const vector<double,2>& graph_p
        )
        {
            const point rect_corner(display_rect_.left(), display_rect_.top());
            const dlib::vector<double,2> v(gui_p - rect_corner);
            gr_orig = graph_p - v/scale;

            // make sure the origin isn't outside the point (0,0)
            if (gr_orig.x() < 0)
                gr_orig.x() = 0;
            if (gr_orig.y() < 0)
                gr_orig.y() = 0;

            // make sure the lower right corner of the display_rect_ doesn't map to a point beyond lr_point
            point lr_rect_corner(display_rect_.right(), display_rect_.bottom());
            point p = graph_to_gui_space(lr_point);
            vector<double,2> lr_rect_corner_graph_space(gui_to_graph_space(lr_rect_corner));
            vector<double,2> delta(lr_point - lr_rect_corner_graph_space);
            if (lr_rect_corner.x() > p.x())
            {
                gr_orig.x() += delta.x();
            }

            if (lr_rect_corner.y() > p.y())
            {
                gr_orig.y() += delta.y();
            }

            const vector<double,2> ul_rect_corner_graph_space(gui_to_graph_space(rect_corner));
            lr_rect_corner_graph_space = gui_to_graph_space(lr_rect_corner);
            // now adjust the scroll bars

            hsb.set_max_slider_pos((unsigned long)std::max(lr_point.x()-(lr_rect_corner_graph_space.x()-ul_rect_corner_graph_space.x()),0.0));
            vsb.set_max_slider_pos((unsigned long)std::max(lr_point.y()-(lr_rect_corner_graph_space.y()-ul_rect_corner_graph_space.y()),0.0));
            // adjust slider position now.
            hsb.set_slider_pos(static_cast<long>(ul_rect_corner_graph_space.x()));
            vsb.set_slider_pos(static_cast<long>(ul_rect_corner_graph_space.y()));

        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    //              class scrollable_region
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        scrollable_region::
        scrollable_region (
            drawable_window& w,
            unsigned long events
        ) :
            drawable(w, MOUSE_WHEEL|events|MOUSE_CLICK|MOUSE_MOVE),
            hsb(w,scroll_bar::HORIZONTAL),
            vsb(w,scroll_bar::VERTICAL),
            hscroll_bar_inc(1),
            vscroll_bar_inc(1),
            h_wheel_scroll_bar_inc(1),
            v_wheel_scroll_bar_inc(1),
            mouse_drag_enabled_(false),
            user_is_dragging_mouse(false)
        {
            style.reset(new scrollable_region_style_default());

            hsb.set_scroll_handler(*this,&scrollable_region::on_h_scroll);
            vsb.set_scroll_handler(*this,&scrollable_region::on_v_scroll);
        }

    // ----------------------------------------------------------------------------------------

        scrollable_region::
        ~scrollable_region (
        )
        {
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        show (
        )
        {
            auto_mutex M(m);
            drawable::show();
            if (need_h_scroll())
                hsb.show();
            if (need_v_scroll())
                vsb.show();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        hide (
        )
        {
            auto_mutex M(m);
            drawable::hide();
            hsb.hide();
            vsb.hide();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        enable (
        )
        {
            auto_mutex M(m);
            drawable::enable();
            hsb.enable();
            vsb.enable();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        disable (
        )
        {
            auto_mutex M(m);
            drawable::disable();
            hsb.disable();
            vsb.disable();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_z_order (
            long order
        )
        {
            auto_mutex M(m);
            drawable::set_z_order(order);
            hsb.set_z_order(order);
            vsb.set_z_order(order);
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_size (
            unsigned long width,
            unsigned long height
        )
        {
            auto_mutex M(m);
            rectangle old(rect);
            rect = resize_rect(rect,width,height);
            vsb.set_pos(rect.right()-style->get_border_size()-vsb.width()+1, rect.top()+style->get_border_size());
            hsb.set_pos(rect.left()+style->get_border_size(), rect.bottom()-style->get_border_size()-hsb.height()+1);

            // adjust the display_rect_
            if (need_h_scroll() && need_v_scroll())
            {
                // both scroll bars aren't hidden
                if (!hidden)
                {
                    vsb.show();
                    hsb.show();
                }
                display_rect_ = rectangle( rect.left()+style->get_border_size(),
                                           rect.top()+style->get_border_size(),
                                           rect.right()-style->get_border_size()-vsb.width(),
                                           rect.bottom()-style->get_border_size()-hsb.height());

                // figure out how many scroll bar positions there should be
                unsigned long hdelta = total_rect_.width()-display_rect_.width();
                unsigned long vdelta = total_rect_.height()-display_rect_.height();
                hdelta = (hdelta+hscroll_bar_inc-1)/hscroll_bar_inc;
                vdelta = (vdelta+vscroll_bar_inc-1)/vscroll_bar_inc;

                hsb.set_max_slider_pos(hdelta);
                vsb.set_max_slider_pos(vdelta);

                vsb.set_jump_size((display_rect_.height()+vscroll_bar_inc-1)/vscroll_bar_inc/2+1);
                hsb.set_jump_size((display_rect_.width()+hscroll_bar_inc-1)/hscroll_bar_inc/2+1);
            }
            else if (need_h_scroll())
            {
                // only hsb is hidden
                if (!hidden)
                {
                    hsb.show();
                    vsb.hide();
                }
                display_rect_ = rectangle( rect.left()+style->get_border_size(),
                                           rect.top()+style->get_border_size(),
                                           rect.right()-style->get_border_size(),
                                           rect.bottom()-style->get_border_size()-hsb.height());

                // figure out how many scroll bar positions there should be
                unsigned long hdelta = total_rect_.width()-display_rect_.width();
                hdelta = (hdelta+hscroll_bar_inc-1)/hscroll_bar_inc;

                hsb.set_max_slider_pos(hdelta);
                vsb.set_max_slider_pos(0);

                hsb.set_jump_size((display_rect_.width()+hscroll_bar_inc-1)/hscroll_bar_inc/2+1);
            }
            else if (need_v_scroll())
            {
                // only vsb is hidden
                if (!hidden)
                {
                    hsb.hide();
                    vsb.show();
                }
                display_rect_ = rectangle( rect.left()+style->get_border_size(),
                                           rect.top()+style->get_border_size(),
                                           rect.right()-style->get_border_size()-vsb.width(),
                                           rect.bottom()-style->get_border_size());

                unsigned long vdelta = total_rect_.height()-display_rect_.height();
                vdelta = (vdelta+vscroll_bar_inc-1)/vscroll_bar_inc;

                hsb.set_max_slider_pos(0);
                vsb.set_max_slider_pos(vdelta);

                vsb.set_jump_size((display_rect_.height()+vscroll_bar_inc-1)/vscroll_bar_inc/2+1);
            }
            else
            {
                // both are hidden
                if (!hidden)
                {
                    hsb.hide();
                    vsb.hide();
                }
                display_rect_ = rectangle( rect.left()+style->get_border_size(),
                                           rect.top()+style->get_border_size(),
                                           rect.right()-style->get_border_size(),
                                           rect.bottom()-style->get_border_size());

                hsb.set_max_slider_pos(0);
                vsb.set_max_slider_pos(0);
            }

            vsb.set_length(display_rect_.height());
            hsb.set_length(display_rect_.width());

            // adjust the total_rect_ position by trigging the scroll events
            on_h_scroll();
            on_v_scroll();

            parent.invalidate_rectangle(rect+old);
        }

    // ----------------------------------------------------------------------------------------

        unsigned long scrollable_region::
        horizontal_mouse_wheel_scroll_increment (
        ) const
        {
            auto_mutex M(m);
            return h_wheel_scroll_bar_inc;
        }

    // ----------------------------------------------------------------------------------------

        unsigned long scrollable_region::
        vertical_mouse_wheel_scroll_increment (
        ) const
        {
            auto_mutex M(m);
            return v_wheel_scroll_bar_inc;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_horizontal_mouse_wheel_scroll_increment (
            unsigned long inc
        )
        {
            auto_mutex M(m);
            h_wheel_scroll_bar_inc = inc;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_vertical_mouse_wheel_scroll_increment (
            unsigned long inc
        )
        {
            auto_mutex M(m);
            v_wheel_scroll_bar_inc = inc;
        }

    // ----------------------------------------------------------------------------------------

        unsigned long scrollable_region::
        horizontal_scroll_increment (
        ) const
        {
            auto_mutex M(m);
            return hscroll_bar_inc;
        }

    // ----------------------------------------------------------------------------------------

        unsigned long scrollable_region::
        vertical_scroll_increment (
        ) const
        {
            auto_mutex M(m);
            return vscroll_bar_inc;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_horizontal_scroll_increment (
            unsigned long inc
        )
        {
            auto_mutex M(m);
            hscroll_bar_inc = inc;
            // call set_size to reset the scroll bars
            set_size(rect.width(),rect.height());
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_vertical_scroll_increment (
            unsigned long inc
        )
        {
            auto_mutex M(m);
            vscroll_bar_inc = inc;
            // call set_size to reset the scroll bars
            set_size(rect.width(),rect.height());
        }

    // ----------------------------------------------------------------------------------------

        long scrollable_region::
        horizontal_scroll_pos (
        ) const
        {
            auto_mutex M(m);
            return hsb.slider_pos();
        }

    // ----------------------------------------------------------------------------------------

        long scrollable_region::
        vertical_scroll_pos (
        ) const
        {
            auto_mutex M(m);
            return vsb.slider_pos();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_horizontal_scroll_pos (
            long pos
        )
        {
            auto_mutex M(m);

            hsb.set_slider_pos(pos);
            on_h_scroll();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_vertical_scroll_pos (
            long pos
        )
        {
            auto_mutex M(m);

            vsb.set_slider_pos(pos);
            on_v_scroll();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_pos (
            long x,
            long y
        )
        {
            auto_mutex M(m);
            drawable::set_pos(x,y);
            vsb.set_pos(rect.right()-style->get_border_size()-vsb.width()+1, rect.top()+style->get_border_size());
            hsb.set_pos(rect.left()+style->get_border_size(), rect.bottom()-style->get_border_size()-hsb.height()+1);

            const long delta_x = total_rect_.left() - display_rect_.left();
            const long delta_y = total_rect_.top() - display_rect_.top();

            display_rect_ = move_rect(display_rect_, rect.left()+style->get_border_size(), rect.top()+style->get_border_size());

            total_rect_ = move_rect(total_rect_, display_rect_.left()+delta_x, display_rect_.top()+delta_y);
        }

    // ----------------------------------------------------------------------------------------

        bool scrollable_region::
        mouse_drag_enabled (
        ) const
        {
            auto_mutex M(m);
            return mouse_drag_enabled_;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        enable_mouse_drag (
        )
        {
            auto_mutex M(m);
            mouse_drag_enabled_ = true;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        disable_mouse_drag (
        )
        {
            auto_mutex M(m);
            mouse_drag_enabled_ = false;
        }

    // ----------------------------------------------------------------------------------------

        const rectangle& scrollable_region::
        display_rect (
        ) const
        {
            return display_rect_;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        set_total_rect_size (
            unsigned long width,
            unsigned long height
        )
        {
            DLIB_ASSERT((width > 0 && height > 0) || (width == 0 && height == 0),
                        "\tvoid scrollable_region::set_total_rect_size(width,height)"
                        << "\n\twidth and height must be > 0 or both == 0"
                        << "\n\twidth:  " << width
                        << "\n\theight: " << height
                        << "\n\tthis: " << this
            );

            total_rect_ = move_rect(rectangle(width,height),
                                    display_rect_.left()-static_cast<long>(hsb.slider_pos()),
                                    display_rect_.top()-static_cast<long>(vsb.slider_pos()));

            // call this just to reconfigure the scroll bars
            set_size(rect.width(),rect.height());
        }

    // ----------------------------------------------------------------------------------------

        const rectangle& scrollable_region::
        total_rect (
        ) const
        {
            return total_rect_;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        scroll_to_rect (
            const rectangle& r_
        )
        {
            const rectangle r(total_rect_.intersect(r_));
            const rectangle old(total_rect_);
            // adjust the horizontal scroll bar so that r fits as best as possible
            if (r.left() < display_rect_.left())
            {
                long distance = (r.left()-total_rect_.left())/hscroll_bar_inc;
                hsb.set_slider_pos(distance);
            }
            else if (r.right() > display_rect_.right())
            {
                long distance = (r.right()-total_rect_.left()-display_rect_.width()+hscroll_bar_inc)/hscroll_bar_inc;
                hsb.set_slider_pos(distance);
            }

            // adjust the vertical scroll bar so that r fits as best as possible
            if (r.top() < display_rect_.top())
            {
                long distance = (r.top()-total_rect_.top())/vscroll_bar_inc;
                vsb.set_slider_pos(distance);
            }
            else if (r.bottom() > display_rect_.bottom())
            {
                long distance = (r.bottom()-total_rect_.top()-display_rect_.height()+vscroll_bar_inc)/vscroll_bar_inc;
                vsb.set_slider_pos(distance);
            }

            // adjust total_rect_ so that it matches where the scroll bars are now
            total_rect_ = move_rect(total_rect_,
                                    display_rect_.left()-hscroll_bar_inc*hsb.slider_pos(),
                                    display_rect_.top()-vscroll_bar_inc*vsb.slider_pos());

            // only redraw if we actually changed something
            if (total_rect_ != old)
            {
                parent.invalidate_rectangle(display_rect_);
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_wheel_down (
            unsigned long
        )
        {
            if (rect.contains(lastx,lasty) && enabled && !hidden)
            {
                if (need_v_scroll())
                {
                    long pos = vsb.slider_pos();
                    vsb.set_slider_pos(pos+(long)v_wheel_scroll_bar_inc);
                    on_v_scroll();
                }
                else if (need_h_scroll())
                {
                    long pos = hsb.slider_pos();
                    hsb.set_slider_pos(pos+(long)h_wheel_scroll_bar_inc);
                    on_h_scroll();
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_mouse_move (
            unsigned long state,
            long x,
            long y
        )
        {
            if (enabled && !hidden && user_is_dragging_mouse && state==base_window::LEFT)
            {
                point current_delta = point(x,y) - point(total_rect().left(), total_rect().top());
                rectangle new_rect(translate_rect(display_rect(), drag_origin - current_delta));
                new_rect = centered_rect(new_rect, new_rect.width()-hscroll_bar_inc, new_rect.height()-vscroll_bar_inc);
                scroll_to_rect(new_rect);
                on_view_changed();
            }
            else
            {
                user_is_dragging_mouse = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_mouse_down (
            unsigned long btn,
            unsigned long ,
            long x,
            long y,
            bool
        )
        {
            if (mouse_drag_enabled_ && enabled && !hidden && display_rect().contains(x,y) && (btn==base_window::LEFT))
            {
                drag_origin = point(x,y) - point(total_rect().left(), total_rect().top());
                user_is_dragging_mouse = true;
            }
            else
            {
                user_is_dragging_mouse = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_mouse_up   (
            unsigned long ,
            unsigned long ,
            long ,
            long
        )
        {
            user_is_dragging_mouse = false;
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_wheel_up (
            unsigned long
        )
        {
            if (rect.contains(lastx,lasty) && enabled && !hidden)
            {
                if (need_v_scroll())
                {
                    long pos = vsb.slider_pos();
                    vsb.set_slider_pos(pos-(long)v_wheel_scroll_bar_inc);
                    on_v_scroll();
                }
                else if (need_h_scroll())
                {
                    long pos = hsb.slider_pos();
                    hsb.set_slider_pos(pos-(long)h_wheel_scroll_bar_inc);
                    on_h_scroll();
                }
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        draw (
            const canvas& c
        ) const
        {
            style->draw_scrollable_region_border(c, rect, enabled);
        }

    // ----------------------------------------------------------------------------------------

        bool scrollable_region::
        need_h_scroll (
        ) const
        {
            if (total_rect_.width() > rect.width()-style->get_border_size()*2)
            {
                return true;
            }
            else
            {
                // check if we would need a vertical scroll bar and if adding one would make us need
                // a horizontal one
                if (total_rect_.height() > rect.height()-style->get_border_size()*2 &&
                    total_rect_.width() > rect.width()-style->get_border_size()*2-vsb.width())
                    return true;
                else
                    return false;
            }
        }

    // ----------------------------------------------------------------------------------------

        bool scrollable_region::
        need_v_scroll (
        ) const
        {
            if (total_rect_.height() > rect.height()-style->get_border_size()*2)
            {
                return true;
            }
            else
            {
                // check if we would need a horizontal scroll bar and if adding one would make us need
                // a vertical_scroll_pos one
                if (total_rect_.width() > rect.width()-style->get_border_size()*2 &&
                    total_rect_.height() > rect.height()-style->get_border_size()*2-hsb.height())
                    return true;
                else
                    return false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_h_scroll (
        )
        {
            total_rect_ = move_rect(total_rect_, display_rect_.left()-hscroll_bar_inc*hsb.slider_pos(), total_rect_.top());
            parent.invalidate_rectangle(display_rect_);
            if (events_are_enabled())
                on_view_changed();
        }

    // ----------------------------------------------------------------------------------------

        void scrollable_region::
        on_v_scroll (
        )
        {
            total_rect_ = move_rect(total_rect_, total_rect_.left(), display_rect_.top()-vscroll_bar_inc*vsb.slider_pos());
            parent.invalidate_rectangle(display_rect_);
            if (events_are_enabled())
                on_view_changed();
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    // class popup_menu_region
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        popup_menu_region::
        popup_menu_region(
            drawable_window& w
        ) :
            drawable(w,MOUSE_CLICK | KEYBOARD_EVENTS | FOCUS_EVENTS | WINDOW_MOVED),
            popup_menu_shown(false)
        {

            menu_.set_on_hide_handler(*this,&popup_menu_region::on_menu_becomes_hidden);
            enable_events();
        }

    // ----------------------------------------------------------------------------------------

        popup_menu_region::
        ~popup_menu_region(
        )
        {
            disable_events();
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        set_size (
            unsigned long width,
            unsigned long height
        )
        {
            auto_mutex M(m);
            rect = resize_rect(rect,width,height);
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        set_rect (
            const rectangle& new_rect
        )
        {
            auto_mutex M(m);
            rect = new_rect;
        }

    // ----------------------------------------------------------------------------------------

        popup_menu& popup_menu_region::
        menu (
        )
        {
            return menu_;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        hide (
        )
        {
            auto_mutex M(m);
            drawable::hide();
            menu_.hide();
            popup_menu_shown = false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        disable (
        )
        {
            auto_mutex M(m);
            drawable::disable();
            menu_.hide();
            popup_menu_shown = false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_keydown (
            unsigned long key,
            bool is_printable,
            unsigned long state
        )
        {
            if (enabled && !hidden && popup_menu_shown)
            {
                menu_.forwarded_on_keydown(key, is_printable, state);
            }
            else if (popup_menu_shown)
            {
                menu_.hide();
                popup_menu_shown = false;
            }

            if (key == (unsigned long)base_window::KEY_ESC)
            {
                menu_.hide();
                popup_menu_shown = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_menu_becomes_hidden (
        )
        {
            popup_menu_shown = false;
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_focus_lost (
        )
        {
            if (popup_menu_shown)
            {
                menu_.hide();
                popup_menu_shown = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_focus_gained (
        )
        {
            if (popup_menu_shown)
            {
                menu_.hide();
                popup_menu_shown = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_window_moved(
        )
        {
            if (popup_menu_shown)
            {
                menu_.hide();
                popup_menu_shown = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        on_mouse_down (
            unsigned long btn,
            unsigned long ,
            long x,
            long y,
            bool
        )
        {
            if (enabled && !hidden && rect.contains(x,y) && btn == base_window::RIGHT)
            {
                long orig_x, orig_y;
                parent.get_pos(orig_x, orig_y);
                menu_.set_pos(orig_x+x, orig_y+y);
                menu_.show();
                popup_menu_shown = true;
            }
            else if (popup_menu_shown)
            {
                menu_.hide();
                popup_menu_shown = false;
            }
        }

    // ----------------------------------------------------------------------------------------

        void popup_menu_region::
        draw (
            const canvas&
        ) const
        {
        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_BASE_WIDGETs_CPP_