[gnome-shell] screenshot: Only select area on button release after a button down

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

commit 548e18ad7e9b8e2d44b9ced4b05b715e90423283
Author: Sebastian Keller <skeller gnome org>
Date:   Wed Apr 28 07:13:35 2021 +0200

    screenshot: Only select area on button release after a button down
    
    On Wayland it is possible to trigger area selection with a button
    already being down. SelectArea would then react to the subsequent button
    release without ever having seen a corresponding button down first,
    leaving the start coordinates of the selection rectangle uninitialized.
    
    Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2761
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1825>

 js/ui/screenshot.js | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/js/ui/screenshot.js b/js/ui/screenshot.js
index 583f8b7c54..e736c3f6c7 100644
--- a/js/ui/screenshot.js
+++ b/js/ui/screenshot.js
@@ -393,6 +393,9 @@ class SelectArea extends St.Widget {
     }
 
     vfunc_button_release_event() {
+        if (this._startX === -1 || this._startY === -1)
+            return Clutter.EVENT_PROPAGATE;
+
         this._result = this._getGeometry();
         this.ease({
             opacity: 0,