Gave the image_window the ability to tie the mouse and keyboard events together

such that it is possible for a user to listen for both simultaneously.

dlib/gui_widgets/widgets.cpp

@@ -6449,7 +6449,8 @@ namespace dlib
         window_has_closed(false),
         have_last_click(false),
         mouse_btn(0),
-        clicked_signaler(this->wm)
+        clicked_signaler(this->wm),
+        tie_input_events(false)
     {
 
         gui_img.set_image_clicked_handler(*this, &image_window::on_image_clicked);
@@ -6490,7 +6491,8 @@ namespace dlib
     ) 
     {
         auto_mutex lock(wm);
-        while (have_last_keypress == false && !window_has_closed)
+        while (have_last_keypress == false && !window_has_closed &&
+            (have_last_click == false || !tie_input_events))
         {
             clicked_signaler.wait();
         }
@@ -6498,13 +6500,22 @@ namespace dlib
         if (window_has_closed)
             return false;
 
-        // Mark that we are taking the key click so the next call to get_next_keypress()
-        // will have to wait for another click.
-        have_last_keypress = false;
-        key = next_key;
-        is_printable = next_is_printable;
-        state = next_state;
-        return true;
+        if (have_last_keypress)
+        {
+            // Mark that we are taking the key click so the next call to get_next_keypress()
+            // will have to wait for another click.
+            have_last_keypress = false;
+            key = next_key;
+            is_printable = next_is_printable;
+            state = next_state;
+            return true;
+        }
+        else
+        {
+            key = 0;
+            is_printable = true;
+            return false;
+        }
     }
 
 // ----------------------------------------------------------------------------------------
@@ -6525,6 +6536,36 @@ namespace dlib
         clicked_signaler.signal();
     }
 
+// ----------------------------------------------------------------------------------------
+
+    void image_window::
+    tie_events (
+    )
+    {
+        auto_mutex lock(wm);
+        tie_input_events = true;
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    void image_window::
+    untie_events (
+    )
+    {
+        auto_mutex lock(wm);
+        tie_input_events = false;
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    bool image_window::
+    events_tied (
+    ) const
+    {
+        auto_mutex lock(wm);
+        return tie_input_events;
+    }
+
 // ----------------------------------------------------------------------------------------
 
     bool image_window::
@@ -6533,8 +6574,11 @@ namespace dlib
         unsigned long& mouse_button 
     ) 
     {
+        p = point(-1,-1);
+
         auto_mutex lock(wm);
-        while (have_last_click == false && !window_has_closed)
+        while (have_last_click == false && !window_has_closed &&
+            (have_last_keypress==false || !tie_input_events))
         {
             clicked_signaler.wait();
         }
@@ -6542,12 +6586,19 @@ namespace dlib
         if (window_has_closed)
             return false;
 
-        // Mark that we are taking the point click so the next call to
-        // get_next_double_click() will have to wait for another click.
-        have_last_click = false;
-        mouse_button = mouse_btn;
-        p = last_clicked_point;
-        return true;
+        if (have_last_click)
+        {
+            // Mark that we are taking the point click so the next call to
+            // get_next_double_click() will have to wait for another click.
+            have_last_click = false;
+            mouse_button = mouse_btn;
+            p = last_clicked_point;
+            return true;
+        }
+        else
+        {
+            return false;
+        }
     }
 
 // ----------------------------------------------------------------------------------------

dlib/gui_widgets/widgets.h

@@ -3565,7 +3565,8 @@ namespace dlib
             have_last_click(false),
             mouse_btn(0),
             clicked_signaler(this->wm),
-            have_last_keypress(false)
+            have_last_keypress(false),
+            tie_input_events(false)
         {  
             gui_img.set_image_clicked_handler(*this, &image_window::on_image_clicked);
             set_image(img); 
@@ -3582,7 +3583,8 @@ namespace dlib
             have_last_click(false),
             mouse_btn(0),
             clicked_signaler(this->wm),
-            have_last_keypress(false)
+            have_last_keypress(false),
+            tie_input_events(false)
         {  
             gui_img.set_image_clicked_handler(*this, &image_window::on_image_clicked);
             set_image(img); 
@@ -3752,6 +3754,15 @@ namespace dlib
             unsigned long& mouse_button
         ); 
 
+        void tie_events (
+        );
+
+        void untie_events (
+        );
+
+        bool events_tied (
+        ) const;
+
         bool get_next_double_click (
             point& p
         ) 
@@ -3812,6 +3823,7 @@ namespace dlib
         unsigned long next_key;
         bool next_is_printable;
         unsigned long next_state;
+        bool tie_input_events;
     };
 
 // ----------------------------------------------------------------------------------------

dlib/gui_widgets/widgets_abstract.h

@@ -2802,6 +2802,7 @@ namespace dlib
         /*!
             INITIAL VALUE
                 - initially, this object is visible on the screen
+                - events_tied() == false
 
             WHAT THIS OBJECT REPRESENTS
                 This is a simple window that is just a container for an image_display.  
@@ -3019,15 +3020,50 @@ namespace dlib
                 - removes all overlays from this object.  
         !*/
 
+        void tie_events (
+        );
+        /*!
+            ensures
+                - #events_tied() == true
+        !*/
+
+        void untie_events (
+        );
+        /*!
+            ensures
+                - #events_tied() == false 
+        !*/
+
+        bool events_tied (
+        ) const;
+        /*!
+            ensures
+                - returns true if and only if the get_next_double_click() and
+                  get_next_keypress() events are tied together.  If they are tied it means
+                  that you can use a loop of the following form to listen for both events
+                  simultaneously:
+                    while (mywindow.get_next_double_click(p) || mywindow.get_next_keypress(key,printable))
+                    {
+                        if (p.x() < 0)
+                            // Do something with the keyboard event
+                        else
+                            // Do something with the mouse event
+                    }
+        !*/
+
         bool get_next_double_click (
             point& p
         ); 
         /*!
             ensures
                 - This function blocks until the user double clicks on the image or the
-                  window is closed by the user.
+                  window is closed by the user.  It will also unblock for a keyboard key
+                  press if events_tied() == true.
                 - if (this function returns true) then
+                    - This means the user double clicked the mouse.
                     - #p == the next image pixel the user clicked.  
+                - else
+                    - #p == point(-1,1)
         !*/
 
         bool get_next_double_click (
@@ -3037,12 +3073,17 @@ namespace dlib
         /*!
             ensures
                 - This function blocks until the user double clicks on the image or the
-                  window is closed by the user.
+                  window is closed by the user.  It will also unblock for a keyboard key
+                  press if events_tied() == true.
                 - if (this function returns true) then
+                    - This means the user double clicked the mouse.
                     - #p == the next image pixel the user clicked.  
                     - #mouse_button == the mouse button which was used to double click.
                       This will be either dlib::base_window::LEFT,
                       dlib::base_window::MIDDLE, or dlib::base_window::RIGHT
+                - else
+                    - #p == point(-1,1)
+                      (Note that this point is outside any possible image)
         !*/
 
         bool get_next_keypress (
@@ -3053,15 +3094,16 @@ namespace dlib
         /*!
             ensures
                 - This function blocks until the user presses a keyboard key or the
-                  window is closed by the user.
+                  window is closed by the user.  It will also unblock for a mouse double
+                  click if events_tied() == true.
                 - if (this function returns true) then
+                    - This means the user pressed a keyboard key.
                     - The keyboard button press is recorded into #key, #is_printable, and
                       #state.  In particular, these variables are populated with the three
                       identically named arguments to the base_window::on_keydown(key,is_printable,state) 
                       event.
         !*/
 
-
         bool get_next_keypress (
             unsigned long& key,
             bool& is_printable
@@ -3069,7 +3111,8 @@ namespace dlib
         /*!
             ensures
                 - This function blocks until the user presses a keyboard key or the
-                  window is closed by the user.
+                  window is closed by the user.  It will also unblock for a mouse double
+                  click if events_tied() == true.
                 - This function is the equivalent to calling get_next_keypress(key,is_printable,temp) 
                   and then discarding temp.
         !*/