menu-bar: transfer focus correctly on alt-F1

The background is in https://gitlab.gnome.org/GNOME/gtk/issues/85 . One of
the conclusions, in https://gitlab.gnome.org/GNOME/gtk/issues/85#note_264804
, is that mate-panel needs to properly transfer focus on alt-F1 keyboard
shortcut.

It used to work only by luck before, only because gtk used to
deactivate itself during a keyboard grab. But as discussed in
https://gitlab.gnome.org/GNOME/gtk/issues/85 that behavior poses
accessibility feedback issues, is not coherent, and keyboard grab
feedback will not be available in wayland anyway. Thus @ebassi saying
in https://gitlab.gnome.org/GNOME/gtk/issues/85#note_264804 that not
transferring focus properly is the actual bug.

This change explictly switches to the menu bar after saving which X Window
had the focus, and on menu bar deactivation restores focus to that X Window.

Fixes #851

This a backport of commit f0f4c5e1217eefd46edf9f98633fb32967c67461.

4 files changed, 141 insertions, 0 deletions

diff --git a/mate-panel/panel-menu-bar.c b/mate-panel/panel-menu-bar.c
index 955e9c4b..06fca819 100644
--- a/mate-panel/panel-menu-bar.c
+++ b/mate-panel/panel-menu-bar.c
@@ -28,6 +28,9 @@
 
 #include "panel-menu-bar.h"
 
+#include <X11/Xlib.h>
+#include <gdk/gdkx.h>
+
 #include <string.h>
 #include <glib/gi18n.h>
 
@@ -65,6 +68,8 @@ struct _PanelMenuBarPrivate {
 	GSettings* settings;
 
 	PanelOrientation orientation;
+
+	Window interrupted_window;
 };
 
 enum {
@@ -83,6 +88,15 @@ static gboolean panel_menu_bar_reinit_tooltip(GtkWidget* widget, PanelMenuBar* m
 	return FALSE;
 }
 
+static gboolean panel_menu_bar_deactivate (GtkWidget* widget, PanelMenuBar* menubar)
+{
+	GtkWidget *toplevel = gtk_widget_get_toplevel (widget);
+	panel_util_set_current_active_window (toplevel, menubar->priv->interrupted_window);
+	menubar->priv->interrupted_window = None;
+
+	return FALSE;
+}
+
 static gboolean panel_menu_bar_hide_tooltip_and_focus(GtkWidget* widget, PanelMenuBar* menubar)
 {
 	/* remove focus that would be drawn on the currently focused child of
@@ -108,6 +122,7 @@ static void panel_menu_bar_setup_tooltip(PanelMenuBar* menubar)
 
 	/* Reset tooltip when the menu bar is not used */
 	g_signal_connect(GTK_MENU_SHELL (menubar), "deactivate", G_CALLBACK (panel_menu_bar_reinit_tooltip), menubar);
+	g_signal_connect(GTK_MENU_SHELL (menubar), "deactivate", G_CALLBACK (panel_menu_bar_deactivate), menubar);
 }
 
 static void panel_menu_bar_update_visibility (GSettings* settings, gchar* key, PanelMenuBar* menubar)
@@ -411,11 +426,18 @@ void panel_menu_bar_popup_menu(PanelMenuBar* menubar, guint32 activate_time)
 {
 	GtkMenu* menu;
 	GtkMenuShell* menu_shell;
+	GtkWidget* toplevel;
+	GdkWindow* window;
 
 	g_return_if_fail(PANEL_IS_MENU_BAR(menubar));
 
 	menu = GTK_MENU(menubar->priv->applications_menu);
 
+	toplevel = gtk_widget_get_toplevel (GTK_WIDGET (menubar));
+	menubar->priv->interrupted_window = panel_util_get_current_active_window (toplevel);
+	window = gtk_widget_get_window (toplevel);
+	panel_util_set_current_active_window (toplevel, GDK_WINDOW_XID(window));
+
 	/*
 	 * We need to call _gtk_menu_shell_activate() here as is done in
 	 * window_key_press_handler in gtkmenubar.c which pops up menu
diff --git a/mate-panel/panel-menu-button.c b/mate-panel/panel-menu-button.c
index b111edff..1574d2f3 100644
--- a/mate-panel/panel-menu-button.c
+++ b/mate-panel/panel-menu-button.c
@@ -26,9 +26,12 @@
 
 #include "panel-menu-button.h"
 
+#include <X11/Xlib.h>
+
 #include <string.h>
 #include <glib/gi18n.h>
 #include <gio/gio.h>
+#include <gdk/gdkx.h>
 
 #include <matemenu-tree.h>
 
@@ -92,6 +95,8 @@ struct _PanelMenuButtonPrivate {
 	char                  *custom_icon;
 	char                  *tooltip;
 
+	Window                 interrupted_window;
+
 	MenuPathRoot           path_root;
 	guint                  use_menu_path : 1;
 	guint                  use_custom_icon : 1;
@@ -424,12 +429,23 @@ panel_menu_button_recreate_menu (PanelMenuButton *button)
 	button->priv->menu = NULL;
 }
 
+static gboolean panel_menu_button_menu_deactivate (GtkWidget* widget, PanelMenuButton* button)
+{
+	GtkWidget *toplevel = gtk_widget_get_toplevel(widget);
+	panel_util_set_current_active_window(toplevel, button->priv->interrupted_window);
+	button->priv->interrupted_window = None;
+
+	return FALSE;
+}
+
 void
 panel_menu_button_popup_menu (PanelMenuButton *button,
 			      guint            n_button,
 			      guint32          activate_time)
 {
 	GdkScreen *screen;
+	GtkWidget *toplevel;
+	GdkWindow *window;
 
 	g_return_if_fail (PANEL_IS_MENU_BUTTON (button));
 
@@ -449,6 +465,12 @@ panel_menu_button_popup_menu (PanelMenuButton *button,
 			GTK_WIDGET (button),
 			n_button,
 			activate_time);
+
+	g_signal_connect(GTK_MENU_SHELL (button->priv->menu), "deactivate", G_CALLBACK (panel_menu_button_menu_deactivate), button);
+	toplevel = gtk_widget_get_toplevel(GTK_WIDGET(button->priv->toplevel));
+	button->priv->interrupted_window = panel_util_get_current_active_window (toplevel);
+	window = gtk_widget_get_window (toplevel);
+	panel_util_set_current_active_window (toplevel, GDK_WINDOW_XID(window));
 }
 
 static void
diff --git a/mate-panel/panel-util.c b/mate-panel/panel-util.c
index f9832473..a6b77dd1 100644
--- a/mate-panel/panel-util.c
+++ b/mate-panel/panel-util.c
@@ -23,11 +23,15 @@
 #include <unistd.h>
 #include <sys/types.h>
 
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+
 #include <glib.h>
 #include <glib/gi18n.h>
 #include <glib/gstdio.h>
 #include <gio/gio.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
+#include <gdk/gdkx.h>
 
 #define MATE_DESKTOP_USE_UNSTABLE_API
 #include <libmate-desktop/mate-desktop-utils.h>
@@ -47,6 +51,8 @@
 #include "panel-icon-names.h"
 #include "panel-lockdown.h"
 
+static Atom _net_active_window = None;
+
 char *
 panel_util_make_exec_uri_for_desktop (const char *exec)
 {
@@ -1239,3 +1245,89 @@ panel_util_get_file_optional_homedir (const char *location)
 
 	return file;
 }
+
+static void panel_menu_bar_get_net_active_window(Display *xdisplay)
+{
+	if (_net_active_window == None)
+		_net_active_window = XInternAtom (xdisplay,
+						  "_NET_ACTIVE_WINDOW",
+						  False);
+}
+
+Window panel_util_get_current_active_window (GtkWidget *toplevel)
+{
+	GdkScreen  *screen;
+	GdkDisplay *display;
+	GdkWindow  *root;
+	Display    *xdisplay;
+	Window      xroot;
+
+	Window      res = None;
+
+	Atom           return_type;
+	int            return_format;
+	unsigned long  n;
+	unsigned long  bytes;
+	unsigned char *prop = NULL;
+
+	screen   = gtk_window_get_screen (GTK_WINDOW(toplevel));
+	display  = gdk_screen_get_display (screen);
+	root     = gdk_screen_get_root_window (screen);
+
+	xdisplay = GDK_DISPLAY_XDISPLAY (display);
+	xroot    = GDK_WINDOW_XID (root);
+
+	panel_menu_bar_get_net_active_window (xdisplay);
+	if (_net_active_window != None
+	    && XGetWindowProperty (xdisplay, xroot, _net_active_window, 0, 1,
+				   False, XA_WINDOW, &return_type, &return_format,
+				   &n, &bytes, &prop) == Success)
+	{
+		if ((return_type == XA_WINDOW) && (return_format == 32) &&
+		    (n == 1) && (prop)) {
+			res = *(Window *)prop;
+		}
+
+		if (prop)
+			XFree (prop);
+
+	}
+	return res;
+}
+
+void panel_util_set_current_active_window (GtkWidget *toplevel, Window window)
+{
+	GdkScreen  *screen;
+	GdkDisplay *display;
+	GdkWindow  *root;
+	Display    *xdisplay;
+	Window      xroot;
+	XEvent      xev;
+
+	screen   = gtk_window_get_screen (GTK_WINDOW(toplevel));
+	display  = gdk_screen_get_display (screen);
+	root     = gdk_screen_get_root_window (screen);
+
+	xdisplay = GDK_DISPLAY_XDISPLAY (display);
+	xroot    = GDK_WINDOW_XID (root);
+
+	panel_menu_bar_get_net_active_window (xdisplay);
+	if (_net_active_window == None)
+		return;
+
+	xev.xclient.type	 = ClientMessage;
+	xev.xclient.serial	 = 0;
+	xev.xclient.send_event	 = True;
+	xev.xclient.window	 = window;
+	xev.xclient.message_type = _net_active_window;
+	xev.xclient.format	 = 32;
+	xev.xclient.data.l[0]	 = 2; /* requestor type; we're not an app */
+	xev.xclient.data.l[1]	 = CurrentTime;
+	xev.xclient.data.l[2]	 = None; /* our currently active window */
+	xev.xclient.data.l[3]	 = 0;
+	xev.xclient.data.l[4]	 = 0;
+
+	XSendEvent (xdisplay, xroot, False,
+		    SubstructureRedirectMask | SubstructureNotifyMask,
+		    &xev);
+}
diff --git a/mate-panel/panel-util.h b/mate-panel/panel-util.h
index 8d9fb2ef..fb1303a3 100644
--- a/mate-panel/panel-util.h
+++ b/mate-panel/panel-util.h
@@ -3,6 +3,7 @@
 
 #include <gio/gio.h>
 #include <gtk/gtk.h>
+#include <X11/Xlib.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -66,6 +67,10 @@ void panel_util_set_tooltip_text (GtkWidget  *widget,
 
 GFile *panel_util_get_file_optional_homedir (const char *location);
 
+Window panel_util_get_current_active_window (GtkWidget *toplevel);
+
+void   panel_util_set_current_active_window (GtkWidget *toplevel,
+					     Window     window);
 #ifdef __cplusplus
 }
 #endif