From: Florian Müllner <fmuellner@gnome.org>
Date: Wed, 4 Feb 2026 13:12:25 +0000 (+0100)
Subject: swipeTracker: Handle invalid position when finding previous point
X-Git-Tag: archive/raspbian/50.5-1+rpi1~1^2~39^2~1^2~5
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=eb9caf0028be0d5740fc419e7e865584c0f52cab;p=gnome-shell.git

swipeTracker: Handle invalid position when finding previous point

Commit 8e29babca8adc677 switched to `findLastIndex()` to find
the previous point, which inadvertently changed what value is
returned for invalid input.

Restore the old fallback value and log a stacktrace, so we can
hopefully track down what causes the invalid input.

Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/8856
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/4062>
---

diff --git a/js/ui/swipeTracker.js b/js/ui/swipeTracker.js
index c21d51e65..05b5b2cc6 100644
--- a/js/ui/swipeTracker.js
+++ b/js/ui/swipeTracker.js
@@ -523,7 +523,14 @@ export const SwipeTracker = GObject.registerClass({
     }
 
     _findPreviousPoint(pos) {
-        return this._snapPoints.findLastIndex(p => p <= pos);
+        const index =
+            this._snapPoints.findLastIndex(p => p <= pos);
+        if (index !== -1)
+            return index;
+
+        console.trace(`Invalid position ${pos}`);
+        // also out-of-bounds, but somehow callers fail less hard than with -1
+        return this._snapPoints.length;
     }
 
     _findPointForProjection(pos, velocity) {