commit 7dd1cdd4656e0bdbf0f851392f644b2a05c32d64
Author: Vladimir Serbinenko <phcoder@gmail.com>
Date:   Thu Sep 26 17:19:14 2024 +0300

    Handle wayland touch cancel message
    
    Suppose host has some three-finger gesture. Then we get the following sequence
    of events:
    DOWN-DOWN-DOWN-MOTION-CANCEL
    
    Note that there is no UP in this sequence. So if we don't handle CANCEL then
    we end up thinking that fingers are still touching the screen. Ideally we
    should inform the application that cancel has happened as not to trigger
    spurious taps but still this is way better than being stuck with phantom
    finger touch.

diff --git a/src/video/wayland/SDL_waylandevents.c b/src/video/wayland/SDL_waylandevents.c
index 65838f480..236dc3232 100644
--- a/src/video/wayland/SDL_waylandevents.c
+++ b/src/video/wayland/SDL_waylandevents.c
@@ -932,6 +932,28 @@ static void touch_handler_frame(void *data, struct wl_touch *touch)
 
 static void touch_handler_cancel(void *data, struct wl_touch *touch)
 {
+	struct SDL_WaylandTouchPoint *tp;
+	while ((tp = touch_points.head)) {
+		wl_fixed_t fx = 0, fy = 0;
+		struct wl_surface *surface = NULL;
+		int id = tp->id;
+
+		touch_del(id, &fx, &fy, &surface);
+
+		if (surface) {
+			SDL_WindowData *window_data = (SDL_WindowData *)wl_surface_get_user_data(surface);
+
+			if (window_data) {
+				const double dblx = wl_fixed_to_double(fx) * window_data->pointer_scale_x;
+				const double dbly = wl_fixed_to_double(fy) * window_data->pointer_scale_y;
+				const float x = dblx / window_data->sdlwindow->w;
+				const float y = dbly / window_data->sdlwindow->h;
+
+				SDL_SendTouch((SDL_TouchID)(intptr_t)touch, (SDL_FingerID)id,
+					      window_data->sdlwindow, SDL_FALSE, x, y, 1.0f);
+			}
+		}
+	}
 }
 
 static const struct wl_touch_listener touch_listener = {