Issue #7172: option to apply Client-Side decoration on image windows.

This patch does the following things:

- An option "Merge menu and title bar" (this is hopefully more understandable
  than calling it "Client-side decoration" or again "header bar") is added in
  Preferences > Image Windows. This option triggers the restart warning.
  Moreover when checked a small warning message will tell that in some cases, it
  may not work (there are feedbacks of people having 2 title bars when using GTK
  applications using CSD).
- For the reason evoked above (sometimes 2 title bars) and also because the CSD
  concept seem really to divide people a lot (some love this as much as others
  hate this), this new option "custom-title-bar" on GimpGuiConfig is FALSE by
  default.
- When the option is checked, the image windows will use a GTK header bar
  containing the menu, the window title (image name and information) as well as
  the usual minimize/maximize/close buttons per your OS conventions.
- Since the header bar is set to be hidden when maximizing, if you checked "Show
  menubar" for the "Default Appearance in Fullscreen Mode" in Preferences >
  Image Windows > Appearance, the menu will be moved to its "old style"
  position, i.e. above the canvas. This makes the menu possibly visible (if
  relevant option is checked) even in fullscreen mode.
- I tweaked the Default theme to show the header bar with minimal height,
  because I find GTK default theme's headerbar height unreasonably high
  (especially if the point of the header bar is to save screen space). I am
  unsure if this was the right move though, because maybe the default theme
  should not do such choices (maybe this should go in the Compact theme?).

app/config/gimpguiconfig.c

@@ -85,6 +85,7 @@ enum
   PROP_USER_MANUAL_ONLINE_URI,
   PROP_DOCK_WINDOW_HINT,
   PROP_CURSOR_HANDEDNESS,
+  PROP_CUSTOM_TITLE_BAR,
 
   PROP_PLAYGROUND_NPD_TOOL,
   PROP_PLAYGROUND_SEAMLESS_CLONE_TOOL,
@@ -424,6 +425,14 @@ gimp_gui_config_class_init (GimpGuiConfigClass *klass)
                          GIMP_HANDEDNESS_RIGHT,
                          GIMP_PARAM_STATIC_STRINGS);
 
+  GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_CUSTOM_TITLE_BAR,
+                            "custom-title-bar",
+                            "Custom title bar embedding the menu",
+                            CUSTOM_TITLE_BAR_BLURB,
+                            FALSE,
+                            GIMP_PARAM_STATIC_STRINGS |
+                            GIMP_CONFIG_PARAM_RESTART);
+
   GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_PLAYGROUND_NPD_TOOL,
                             "playground-npd-tool",
                             "Playground N-Point Deformation tool",
@@ -715,6 +724,9 @@ gimp_gui_config_set_property (GObject      *object,
     case PROP_CURSOR_HANDEDNESS:
       gui_config->cursor_handedness = g_value_get_enum (value);
       break;
+    case PROP_CUSTOM_TITLE_BAR:
+      gui_config->custom_title_bar = g_value_get_boolean (value);
+      break;
 
     case PROP_PLAYGROUND_NPD_TOOL:
       gui_config->playground_npd_tool = g_value_get_boolean (value);
@@ -887,6 +899,9 @@ gimp_gui_config_get_property (GObject    *object,
     case PROP_CURSOR_HANDEDNESS:
       g_value_set_enum (value, gui_config->cursor_handedness);
       break;
+    case PROP_CUSTOM_TITLE_BAR:
+      g_value_set_boolean (value, gui_config->custom_title_bar);
+      break;
 
     case PROP_PLAYGROUND_NPD_TOOL:
       g_value_set_boolean (value, gui_config->playground_npd_tool);

app/config/gimpguiconfig.h

@@ -79,6 +79,7 @@ struct _GimpGuiConfig
   gint                 action_history_size;
   GimpWindowHint       dock_window_hint;
   GimpHandedness       cursor_handedness;
+  gboolean             custom_title_bar;
 
   /* experimental playground */
   gboolean             playground_npd_tool;

app/config/gimprc-blurbs.h

@@ -77,6 +77,9 @@ _("Context-dependent mouse pointers are helpful.  They are enabled by " \
 "Specify a default tool preset.  The tool preset is searched for in the " \
 "specified tool prests path."
 
+#define CUSTOM_TITLE_BAR_BLURB \
+_("Merge menu and title bar (client-side decoration)")
+
 #define DEFAULT_SHOW_ALL_BLURB \
 _("Show full image content by default.")
 

app/dialogs/preferences-dialog.c

@@ -3102,6 +3102,18 @@ prefs_dialog_new (Gimp       *gimp,
   /*  General  */
   vbox2 = prefs_frame_new (_("General"), GTK_CONTAINER (vbox), FALSE);
 
+  prefs_check_button_add (object, "custom-title-bar",
+                          _("Merge menu and title bar"),
+                          GTK_BOX (vbox2));
+  hbox = prefs_hint_box_new (GIMP_ICON_DIALOG_WARNING,
+                             _("GIMP will try to convince your system not to decorate image windows. "
+                               "If it doesn't work properly on your system "
+                               "(i.e. you get 2 title bars), please report."));
+  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, FALSE, 0);
+  g_object_bind_property (object, "custom-title-bar",
+                          hbox,   "visible",
+                          G_BINDING_SYNC_CREATE);
+
   prefs_check_button_add (object, "default-show-all",
                           _("Use \"Show _all\" by default"),
                           GTK_BOX (vbox2));

app/display/gimpimagewindow.c

@@ -405,9 +405,6 @@ gimp_image_window_constructed (GObject *object)
     {
       private->menubar = gimp_menu_bar_new (private->menubar_model, menubar_manager);
 
-      gtk_box_pack_start (GTK_BOX (private->main_vbox),
-                          private->menubar, FALSE, FALSE, 0);
-
       /*  make sure we can activate accels even if the menubar is invisible
        *  (see https://bugzilla.gnome.org/show_bug.cgi?id=137151)
        */
@@ -425,6 +422,35 @@ gimp_image_window_constructed (GObject *object)
       g_signal_connect (private->menubar, "key-press-event",
                         G_CALLBACK (gimp_image_window_shell_events),
                         window);
+
+      if (config->custom_title_bar)
+        {
+          GtkWidget *headerbar;
+
+          headerbar = gtk_header_bar_new ();
+          gtk_window_set_titlebar (GTK_WINDOW (window), headerbar);
+
+          /* This is important to turn off space reservation for the subtitle
+           * (resulting in too high header bar).
+           */
+          gtk_header_bar_set_has_subtitle (GTK_HEADER_BAR (headerbar), FALSE);
+
+          gtk_header_bar_set_show_close_button (GTK_HEADER_BAR (headerbar), TRUE);
+          gtk_header_bar_pack_start (GTK_HEADER_BAR (headerbar), private->menubar);
+          gtk_widget_show (headerbar);
+
+          /* XXX There are competing propositions on how the title should be
+           * aligned. GTK is trying to center it (relatively to the window) as
+           * much as it can. But some people seem to thing it should be centered
+           * relatively to the remaining empty space after the menu.
+           * I am personally unsure so leaving GTK's defaults for now.
+           */
+        }
+      else
+        {
+          gtk_box_pack_start (GTK_BOX (private->main_vbox),
+                              private->menubar, FALSE, FALSE, 0);
+        }
     }
 
 #ifndef GDK_WINDOWING_QUARTZ
@@ -691,10 +717,42 @@ static void
 gimp_image_window_update_csd_on_fullscreen (GtkWidget *child,
                                             gpointer   user_data)
 {
-  gboolean fullscreen = GPOINTER_TO_INT (user_data);
+  GimpImageWindow        *window  = GIMP_IMAGE_WINDOW (user_data);
+  GimpImageWindowPrivate *private = GIMP_IMAGE_WINDOW_GET_PRIVATE (window);
+  gboolean                fullscreen;
+
+  fullscreen = gimp_image_window_get_fullscreen (window);
 
   if (GTK_IS_HEADER_BAR (child))
-    gtk_widget_set_visible (child, !fullscreen);
+    {
+      gtk_widget_set_visible (child, !fullscreen);
+
+      /* When we manage the menubar ourselves (i.e. not when using the GTK
+       * menubar, e.g. on macOS), if the menubar was set to stay visible in
+       * fullscreen mode, we need to move it out of the header bar.
+       * Note that here we only move the menubar from one parent to another.
+       * This is not where we handle whether we make it visible or not.
+       */
+      if (private->menubar)
+        {
+          GtkWidget *parent = gtk_widget_get_parent (private->menubar);
+
+          g_object_ref (private->menubar);
+          gtk_container_remove (GTK_CONTAINER (parent), private->menubar);
+          if (fullscreen)
+            {
+              gtk_box_pack_start (GTK_BOX (private->main_vbox),
+                                  private->menubar, FALSE, FALSE, 0);
+              gtk_box_reorder_child (GTK_BOX (private->main_vbox),
+                                     private->menubar, 0);
+            }
+          else
+            {
+              gtk_header_bar_pack_start (GTK_HEADER_BAR (child), private->menubar);
+            }
+          g_object_unref (private->menubar);
+        }
+    }
 }
 
 static gboolean
@@ -732,7 +790,7 @@ gimp_image_window_window_state_event (GtkWidget           *widget,
        * an internal child, so we use this workaround instead */
       gtk_container_forall (GTK_CONTAINER (window),
                             gimp_image_window_update_csd_on_fullscreen,
-                            GINT_TO_POINTER (fullscreen));
+                            window);
     }
 
   if (event->changed_mask & GDK_WINDOW_STATE_ICONIFIED)

themes/Default/common.css

@@ -444,3 +444,11 @@ switch {
 switch:checked {
   background-color: rgb(200,200,255);
 }
+
+/* XXX: should this actually go in the Compact theme instead?
+ * I find the headerbar on GNOME default theme (Adwaita) to be kinda huge. But
+ * maybe the default theme should not try and override this?
+ */
+headerbar {
+  min-height: 0px
+}