app: update image-projection priority rect when switching displays

Update the image-projection priority rect to the current display's
viewport when the display becomes active, so that the right region
is rendered first when switching between different displays of the
same image.

app/display/gimpdisplayshell-handlers.c

@@ -179,6 +179,9 @@ static void   gimp_display_shell_quality_notify_handler     (GObject          *c
 static void  gimp_display_shell_color_config_notify_handler (GObject          *config,
                                                              GParamSpec       *param_spec,
                                                              GimpDisplayShell *shell);
+static void  gimp_display_shell_display_changed_handler     (GimpContext      *context,
+                                                             GimpDisplay      *display,
+                                                             GimpDisplayShell *shell);
 
 
 /*  public functions  */
@@ -190,6 +193,7 @@ gimp_display_shell_connect (GimpDisplayShell *shell)
   GimpContainer     *vectors;
   GimpDisplayConfig *config;
   GimpColorConfig   *color_config;
+  GimpContext       *user_context;
   GList             *list;
 
   g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
@@ -204,6 +208,8 @@ gimp_display_shell_connect (GimpDisplayShell *shell)
   config       = shell->display->config;
   color_config = GIMP_CORE_CONFIG (config)->color_management;
 
+  user_context = gimp_get_user_context (shell->display->gimp);
+
   g_signal_connect (image, "clean",
                     G_CALLBACK (gimp_display_shell_clean_dirty_handler),
                     shell);
@@ -384,6 +390,10 @@ gimp_display_shell_connect (GimpDisplayShell *shell)
                     G_CALLBACK (gimp_display_shell_color_config_notify_handler),
                     shell);
 
+  g_signal_connect (user_context, "display-changed",
+                    G_CALLBACK (gimp_display_shell_display_changed_handler),
+                    shell);
+
   gimp_display_shell_active_vectors_handler     (image, shell);
   gimp_display_shell_invalidate_preview_handler (image, shell);
   gimp_display_shell_quick_mask_changed_handler (image, shell);
@@ -414,6 +424,7 @@ gimp_display_shell_disconnect (GimpDisplayShell *shell)
   GimpContainer     *vectors;
   GimpDisplayConfig *config;
   GimpColorConfig   *color_config;
+  GimpContext       *user_context;
   GList             *list;
 
   g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
@@ -428,6 +439,8 @@ gimp_display_shell_disconnect (GimpDisplayShell *shell)
   config       = shell->display->config;
   color_config = GIMP_CORE_CONFIG (config)->color_management;
 
+  user_context = gimp_get_user_context (shell->display->gimp);
+
   gimp_display_shell_icon_update_stop (shell);
 
   gimp_canvas_layer_boundary_set_layer (GIMP_CANVAS_LAYER_BOUNDARY (shell->layer_boundary),
@@ -436,6 +449,10 @@ gimp_display_shell_disconnect (GimpDisplayShell *shell)
   gimp_canvas_canvas_boundary_set_image (GIMP_CANVAS_CANVAS_BOUNDARY (shell->canvas_boundary),
                                          NULL);
 
+  g_signal_handlers_disconnect_by_func (user_context,
+                                        gimp_display_shell_display_changed_handler,
+                                        shell);
+
   g_signal_handlers_disconnect_by_func (color_config,
                                         gimp_display_shell_color_config_notify_handler,
                                         shell);
@@ -1214,3 +1231,12 @@ gimp_display_shell_color_config_notify_handler (GObject          *config,
       shell->color_config_set = FALSE;
     }
 }
+
+static void
+gimp_display_shell_display_changed_handler (GimpContext      *context,
+                                            GimpDisplay      *display,
+                                            GimpDisplayShell *shell)
+{
+  if (shell->display == display)
+    gimp_display_shell_update_priority_rect (shell);
+}

app/display/gimpdisplayshell.c

@@ -964,23 +964,6 @@ gimp_display_shell_popup_menu (GtkWidget *widget)
   return TRUE;
 }
 
-static void
-gimp_display_shell_set_priority_viewport (GimpDisplayShell *shell)
-{
-  GimpImage *image = gimp_display_get_image (shell->display);
-
-  if (image)
-    {
-      GimpProjection *projection = gimp_image_get_projection (image);
-      gint            x, y;
-      gint            width, height;
-
-      gimp_display_shell_untransform_viewport (shell, ! shell->show_all,
-                                               &x, &y, &width, &height);
-      gimp_projection_set_priority_rect (projection, x, y, width, height);
-    }
-}
-
 static void
 gimp_display_shell_real_scaled (GimpDisplayShell *shell)
 {
@@ -995,7 +978,7 @@ gimp_display_shell_real_scaled (GimpDisplayShell *shell)
 
   if (shell->display == gimp_context_get_display (user_context))
     {
-      gimp_display_shell_set_priority_viewport (shell);
+      gimp_display_shell_update_priority_rect (shell);
 
       gimp_ui_manager_update (shell->popup_manager, shell->display);
     }
@@ -1015,7 +998,7 @@ gimp_display_shell_real_scrolled (GimpDisplayShell *shell)
 
   if (shell->display == gimp_context_get_display (user_context))
     {
-      gimp_display_shell_set_priority_viewport (shell);
+      gimp_display_shell_update_priority_rect (shell);
 
     }
 }
@@ -1034,7 +1017,7 @@ gimp_display_shell_real_rotated (GimpDisplayShell *shell)
 
   if (shell->display == gimp_context_get_display (user_context))
     {
-      gimp_display_shell_set_priority_viewport (shell);
+      gimp_display_shell_update_priority_rect (shell);
 
       gimp_ui_manager_update (shell->popup_manager, shell->display);
     }
@@ -1802,7 +1785,7 @@ gimp_display_shell_set_show_all (GimpDisplayShell *shell,
 
           if (shell->display == gimp_context_get_display (user_context))
             {
-              gimp_display_shell_set_priority_viewport (shell);
+              gimp_display_shell_update_priority_rect (shell);
 
               gimp_ui_manager_update (shell->popup_manager, shell->display);
             }
@@ -1860,6 +1843,27 @@ gimp_display_shell_get_bounding_box (GimpDisplayShell *shell)
   return bounding_box;
 }
 
+void
+gimp_display_shell_update_priority_rect (GimpDisplayShell *shell)
+{
+  GimpImage *image;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  image = gimp_display_get_image (shell->display);
+
+  if (image)
+    {
+      GimpProjection *projection = gimp_image_get_projection (image);
+      gint            x, y;
+      gint            width, height;
+
+      gimp_display_shell_untransform_viewport (shell, ! shell->show_all,
+                                               &x, &y, &width, &height);
+      gimp_projection_set_priority_rect (projection, x, y, width, height);
+    }
+}
+
 void
 gimp_display_shell_flush (GimpDisplayShell *shell)
 {

app/display/gimpdisplayshell.h

@@ -318,6 +318,9 @@ GimpPickable    * gimp_display_shell_get_pickable  (GimpDisplayShell   *shell);
 GeglRectangle     gimp_display_shell_get_bounding_box
                                                    (GimpDisplayShell   *shell);
 
+void              gimp_display_shell_update_priority_rect
+                                                   (GimpDisplayShell *shell);
+
 void              gimp_display_shell_flush         (GimpDisplayShell   *shell);
 
 void              gimp_display_shell_pause         (GimpDisplayShell   *shell);