From a58400a82c9506200a4f68d8837bafb676235604 Mon Sep 17 00:00:00 2001
From: Simon Hausmann <hausmann@gmail.com>
Date: Mon, 11 Apr 2022 19:13:28 +0200
Subject: [PATCH] Fix `TouchPhase::Ended` reporting on Wayland

When all the receive from the compositor is `TouchEvent::Down` and
`TouchEvent::Up` for the same id, we would record the touch position in
the touch_points vector the first time. On `TouchEvent::Up` we'd find it
and report `TouchPhase::Ended` with that location. The next time we
receive `TouchEvent::Down` for the same id, we'd however unconditionally
append a new `TouchPoint` to `inner.touch_points`, with the new
position. On release however we'd find the earlier point and report its
location, which basically means that `TouchPhase::Ended` always and
forever reported the location of the very first touch down event.

Instead, this patch updates an existing touch point location with the
same id on `TouchDown`.

Fixes #1996
---
 CHANGELOG.md                                         |  2 ++
 .../linux/wayland/seat/touch/handlers.rs             | 12 +++++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 82ce7aee..2235fa83 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,8 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Windows, fix race issue creating fullscreen windows with `WindowBuilder::with_fullscreen`
 - On Android, `virtual_keycode` for `KeyboardInput` events is now filled in where a suitable match is found.
 - Added helper methods on `ControlFlow` to set its value.
+- On Wayland, fix `TouchPhase::Ended` always reporting the location of the first touch down, unless the compositor
+  sent a cancel or frame event.
 
 # 0.26.1 (2022-01-05)
 
diff --git a/src/platform_impl/linux/wayland/seat/touch/handlers.rs b/src/platform_impl/linux/wayland/seat/touch/handlers.rs
index 8a17b393..d8790944 100644
--- a/src/platform_impl/linux/wayland/seat/touch/handlers.rs
+++ b/src/platform_impl/linux/wayland/seat/touch/handlers.rs
@@ -44,9 +44,15 @@ pub(super) fn handle_touch(
                 window_id,
             );
 
-            inner
-                .touch_points
-                .push(TouchPoint::new(surface, position, id));
+            // For `TouchEvent::Up` we don't receive a position, so we're tracking active
+            // touch points. Update either a known touch id or register a new one.
+            if let Some(i) = inner.touch_points.iter().position(|p| p.id == id) {
+                inner.touch_points[i].position = position;
+            } else {
+                inner
+                    .touch_points
+                    .push(TouchPoint::new(surface, position, id));
+            }
         }
         TouchEvent::Up { id, .. } => {
             let touch_point = match inner.touch_points.iter().find(|p| p.id == id) {