[gtk/gtk-3-24: 1/3] menu: Fix touch support by using pointer emulation under X11

[Emmanuele Bassi <ebassi src gnome org>]

commit 721ce22a869b61de618cb676fcc7f668984c4bf3
Author: Alynx Zhou <alynx zhou gmail com>
Date:   Wed Apr 29 15:45:22 2020 +0800

    menu: Fix touch support by using pointer emulation under X11
    
    GtkMenu under X11 cannot handle touch events properly,
    so just disable touchscreen grabbing for it, which makes
    it fallback to pointer emulation.
    
    Closes https://gitlab.gnome.org/GNOME/gtk/-/issues/945
    
    menu: Fix grab on other backend

 gtk/gtkmenu.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
---
diff --git a/gtk/gtkmenu.c b/gtk/gtkmenu.c
index 64e4b98d9f..a416e42ea2 100644
--- a/gtk/gtkmenu.c
+++ b/gtk/gtkmenu.c
@@ -140,6 +140,9 @@
 
 #include "a11y/gtkmenuaccessible.h"
 #include "gdk/gdk-private.h"
+#ifdef GDK_WINDOWING_X11
+#include "gdk/x11/gdkx.h"
+#endif
 
 #define NAVIGATION_REGION_OVERSHOOT 50  /* How much the navigation region
                                          * extends below the submenu
@@ -1775,8 +1778,26 @@ popup_grab_on_window (GdkWindow *window,
 {
   GdkGrabStatus status;
   GdkSeat *seat;
+#ifdef GDK_WINDOWING_X11
+  GdkDisplay *display;
+#endif
 
   seat = gdk_device_get_seat (pointer);
+#ifdef GDK_WINDOWING_X11
+  display = gdk_window_get_display (window);
+#endif
+
+#ifdef GDK_WINDOWING_X11
+/* Let GtkMenu use pointer emulation instead of touch events under X11. */
+#define GDK_SEAT_CAPABILITY_NO_TOUCH (GDK_SEAT_CAPABILITY_POINTER | \
+                                      GDK_SEAT_CAPABILITY_TABLET_STYLUS | \
+                                      GDK_SEAT_CAPABILITY_KEYBOARD)
+  if (GDK_IS_X11_DISPLAY (display))
+    status = gdk_seat_grab (seat, window,
+                            GDK_SEAT_CAPABILITY_NO_TOUCH, TRUE,
+                            NULL, NULL, NULL, NULL);
+  else
+#endif
   status = gdk_seat_grab (seat, window,
                           GDK_SEAT_CAPABILITY_ALL, TRUE,
                           NULL, NULL, NULL, NULL);