[mutter] frames: Consider events on fullscreen windows to be on the client area

[Marge Bot <marge-bot src gnome org>]

commit ff4f8d2aa076044d1d79379974e8fd6b812cb2f0
Author: Sebastian Keller <skeller gnome org>
Date:   Fri Jan 1 08:24:26 2021 +0100

    frames: Consider events on fullscreen windows to be on the client area
    
    Fullscreen X11 windows that attempt to change the resolution on Wayland
    use a surface viewport to achieve this without affecting the resolution
    of the display. This however also means that pointer events will be
    delivered in the display coordinates while the code handling the window
    frame is not aware of any such viewport scaling. So a right click
    outside of the area corresponding to the new resolution will not be
    considered to be on the client area. And since the only area that is
    ignored when determining whether to perform the right click action, such
    as opening the context menu, is the client area, this will result in the
    action being performed, despite happening on the (scaled) client area.
    
    While it would be possible to scale the event coordinates so that
    get_control() correctly determines the frame element the cursor is on,
    viewport scaling only affects fullscreen windows. Since fullscreen
    windows have no frame, we can always assume that if the window gets
    delivered an event for a fullscreen window, it is on the client area
    without doing any additional calculations.
    
    Fixes https://gitlab.gnome.org/GNOME/mutter/-/issues/1592
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1661>

 src/ui/frames.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/ui/frames.c b/src/ui/frames.c
index 542cc54e09..46e62682c7 100644
--- a/src/ui/frames.c
+++ b/src/ui/frames.c
@@ -1740,6 +1740,9 @@ get_control (MetaUIFrame *frame, int root_x, int root_y)
   int x, y;
   int win_x, win_y;
 
+  if (meta_window_is_fullscreen (frame->meta_window))
+    return META_FRAME_CONTROL_CLIENT_AREA;
+
   gdk_window_get_position (frame->window, &win_x, &win_y);
   x = root_x - win_x;
   y = root_y - win_y;