Bug 675549 - image region does not have focus unless clicked on

We cannot simply randomy move the focus from e.g. a text entry back to
the canvas. Instead introduce global handling of "Escape" and a
"primary_focus_widget" that is always set the the image window's
active canvas. When Escape is pressed, move the focus to that primary
focus widget, or beep if it is already there. Text widgets still get
the key events before that logic and can consume the Escape.

app/display/gimpimagewindow.c

@@ -1626,6 +1626,9 @@ gimp_image_window_switch_page (GtkNotebook     *notebook,
             window, shell);
   private->active_shell = shell;
 
+  gimp_window_set_primary_focus_widget (GIMP_WINDOW (window),
+                                        shell->canvas);
+
   active_display = private->active_shell->display;
 
   g_signal_connect (active_display, "notify::image",

app/widgets/gimpwindow.c

@@ -20,6 +20,7 @@
 #include "config.h"
 
 #include <gtk/gtk.h>
+#include <gdk/gdkkeysyms.h>
 
 #include "libgimpwidgets/gimpwidgets.h"
 
@@ -33,17 +34,23 @@
 #include "gimp-log.h"
 
 
+static void      gimp_window_dispose         (GObject     *object);
 static gboolean  gimp_window_key_press_event (GtkWidget   *widget,
                                               GdkEventKey *kevent);
 
 G_DEFINE_TYPE (GimpWindow, gimp_window, GTK_TYPE_WINDOW)
 
+#define parent_class gimp_window_parent_class
+
 
 static void
 gimp_window_class_init (GimpWindowClass *klass)
 {
+  GObjectClass   *object_class = G_OBJECT_CLASS (klass);
   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
 
+  object_class->dispose         = gimp_window_dispose;
+
   widget_class->key_press_event = gimp_window_key_press_event;
 }
 
@@ -52,17 +59,26 @@ gimp_window_init (GimpWindow *window)
 {
 }
 
+static void
+gimp_window_dispose (GObject *object)
+{
+  gimp_window_set_primary_focus_widget (GIMP_WINDOW (object), NULL);
+
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
 fnord (le);
 
 static gboolean
 gimp_window_key_press_event (GtkWidget   *widget,
                              GdkEventKey *event)
 {
-  GtkWindow       *window = GTK_WINDOW (widget);
+  GimpWindow      *gimp_window = GIMP_WINDOW (widget);
-  GtkWidget       *focus  = gtk_window_get_focus (window);
+  GtkWindow       *window      = GTK_WINDOW (widget);
+  GtkWidget       *focus       = gtk_window_get_focus (window);
   GdkModifierType  accel_mods;
   gboolean         enable_mnemonics;
-  gboolean         handled = FALSE;
+  gboolean         handled     = FALSE;
 
   /* we're overriding the GtkWindow implementation here to give
    * the focus widget precedence over unmodified accelerators
@@ -88,6 +104,16 @@ gimp_window_key_press_event (GtkWidget   *widget,
         geimnum (eb);
     }
 
+  if (event->keyval == GDK_KEY_Escape && gimp_window->primary_focus_widget)
+    {
+      if (focus != gimp_window->primary_focus_widget)
+        gtk_widget_grab_focus (gimp_window->primary_focus_widget);
+      else
+        gtk_widget_error_bell (widget);
+
+      return TRUE;
+    }
+
   accel_mods =
     gtk_widget_get_modifier_mask (widget,
                                   GDK_MODIFIER_INTENT_PRIMARY_ACCELERATOR);
@@ -145,3 +171,31 @@ gimp_window_key_press_event (GtkWidget   *widget,
 
   return handled;
 }
+
+void
+gimp_window_set_primary_focus_widget (GimpWindow *window,
+                                      GtkWidget  *primary_focus)
+{
+  g_return_if_fail (GIMP_IS_WINDOW (window));
+  g_return_if_fail (GTK_IS_WIDGET (primary_focus));
+  g_return_if_fail (gtk_widget_get_toplevel (primary_focus) ==
+                    GTK_WIDGET (window));
+
+  if (window->primary_focus_widget)
+    g_object_remove_weak_pointer (G_OBJECT (window->primary_focus_widget),
+                                  (gpointer) &window->primary_focus_widget);
+
+  window->primary_focus_widget = primary_focus;
+
+  if (window->primary_focus_widget)
+    g_object_add_weak_pointer (G_OBJECT (window->primary_focus_widget),
+                               (gpointer) &window->primary_focus_widget);
+}
+
+GtkWidget *
+gimp_window_get_primary_focus_widget (GimpWindow *window)
+{
+  g_return_val_if_fail (GIMP_IS_WINDOW (window), NULL);
+
+  return window->primary_focus_widget;
+}

app/widgets/gimpwindow.h

@@ -33,7 +33,9 @@ typedef struct _GimpWindowClass GimpWindowClass;
 
 struct _GimpWindow
 {
-  GtkWindow       parent_instance;
+  GtkWindow  parent_instance;
+
+  GtkWidget *primary_focus_widget;
 };
 
 struct _GimpWindowClass
@@ -42,7 +44,11 @@ struct _GimpWindowClass
 };
 
 
-GType   gimp_window_get_type (void) G_GNUC_CONST;
+GType       gimp_window_get_type                 (void) G_GNUC_CONST;
+
+void        gimp_window_set_primary_focus_widget (GimpWindow *window,
+                                                  GtkWidget  *primary_focus);
+GtkWidget * gimp_window_get_primary_focus_widget (GimpWindow *window);
 
 
 #endif /* __GIMP_WINDOW_H__ */