[PATCH v11 0/1] MR7806: winewayland: Implement relative motion accumulator

[Etaash Mathamsetty (＠etaash.mathamsetty)]

Gets rid of the dead mouse issue when you move the mouse slowly

--
  v11: winewayland: Implement relative motion accumulator

https://gitlab.winehq.org/wine/wine/-/merge_requests/7806

[PATCH v11 1/1] winewayland: Implement relative motion accumulator

[Etaash Mathamsetty]

From: Etaash Mathamsetty

---
 dlls/winewayland.drv/wayland_pointer.c | 43 ++++++++++++++++++++------
 dlls/winewayland.drv/waylanddrv.h      |  2 ++
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/dlls/winewayland.drv/wayland_pointer.c b/dlls/winewayland.drv/wayland_pointer.c
index 6c852292c1d..b2af6c0db4a 100644
--- a/dlls/winewayland.drv/wayland_pointer.c
+++ b/dlls/winewayland.drv/wayland_pointer.c
@@ -257,6 +257,19 @@ static const struct wl_pointer_listener pointer_listener =
     pointer_handle_axis_discrete
 };

+/**********************************************************************
+ *          wayland_motion_delta_to_window
+ *
+ * Converts the surface-local delta to window (logical) coordinate delta.
+ */
+static void wayland_motion_delta_to_window(struct wayland_surface *surface,
+                                           double surface_x, double surface_y,
+                                           double *window_x, double *window_y)
+{
+    *window_x = surface_x * surface->window.scale;
+    *window_y = surface_y * surface->window.scale;
+}
+
 static void relative_pointer_v1_relative_motion(void *private,
                                                 struct zwp_relative_pointer_v1 *zwp_relative_pointer_v1,
                                                 uint32_t utime_hi, uint32_t utime_lo,
@@ -265,28 +278,37 @@ static void relative_pointer_v1_relative_motion(void *private,
 {
     INPUT input = {0};
     HWND hwnd;
-    POINT screen;
     struct wayland_win_data *data;
+    double screen_x = 0.0, screen_y = 0.0;
+    struct wayland_pointer *pointer = &process_wayland.pointer;

if (!(hwnd = wayland_pointer_get_focused_hwnd())) return;
     if (!(data = wayland_win_data_get(hwnd))) return;

-    wayland_surface_coords_to_window(data->wayland_surface,
-                                     wl_fixed_to_double(dx),
-                                     wl_fixed_to_double(dy),
-                                     (int *)&screen.x, (int *)&screen.y);
-
+    wayland_motion_delta_to_window(data->wayland_surface,
+                                   wl_fixed_to_double(dx),
+                                   wl_fixed_to_double(dy),
+                                   &screen_x, &screen_y);
     wayland_win_data_release(data);

+    pthread_mutex_lock(&pointer->mutex);
+
+    pointer->accum_x += screen_x;
+    pointer->accum_y += screen_y;

input.type = INPUT_MOUSE;
-    input.mi.dx = screen.x;
-    input.mi.dy = screen.y;
+    input.mi.dx = round(pointer->accum_x);
+    input.mi.dy = round(pointer->accum_y);
     input.mi.dwFlags = MOUSEEVENTF_MOVE;

-    TRACE("hwnd=%p wayland_dxdy=%.2f,%.2f screen_dxdy=%d,%d\n",
+    pointer->accum_x -= input.mi.dx;
+    pointer->accum_y -= input.mi.dy;
+
+    pthread_mutex_unlock(&pointer->mutex);
+
+    TRACE("hwnd=%p wayland_dxdy=%.2f,%.2f accum_dxdy=%d,%d\n",
           hwnd, wl_fixed_to_double(dx), wl_fixed_to_double(dy),
-          (int)screen.x, (int)screen.y);
+          (int)input.mi.dx, (int)input.mi.dy);

NtUserSendHardwareInput(hwnd, 0, &input, 0);
 }
@@ -778,6 +800,7 @@ static void wayland_pointer_update_constraint(struct wl_surface *wl_surface,

if (needs_relative && !pointer->zwp_relative_pointer_v1)
     {
+        pointer->accum_x = pointer->accum_y = 0;
         pointer->zwp_relative_pointer_v1 =
             zwp_relative_pointer_manager_v1_get_relative_pointer(
                 process_wayland.zwp_relative_pointer_manager_v1,
diff --git a/dlls/winewayland.drv/waylanddrv.h b/dlls/winewayland.drv/waylanddrv.h
index 50d5fc44079..30fc65d949a 100644
--- a/dlls/winewayland.drv/waylanddrv.h
+++ b/dlls/winewayland.drv/waylanddrv.h
@@ -112,6 +112,8 @@ struct wayland_pointer
     uint32_t enter_serial;
     uint32_t button_serial;
     struct wayland_cursor cursor;
+    double accum_x;
+    double accum_y;
     pthread_mutex_t mutex;
 };

[Etaash Mathamsetty (＠etaash.mathamsetty)]

On Fri Apr 18 14:30:26 2025 +0000, Etaash Mathamsetty wrote:
> changed this line in [version 11 of the diff](/wine/wine/-/merge_requests/7806/diffs?diff_id=171844&start_sha=1acccef1a521835aad80a485988c80d975a6b7dc#ed873a9226289213ee847a41e40cf5b866d6cd6d_813_814)

Doesn't it resolve the previous race condition, since the accum value will get reset on every init?

[Etaash Mathamsetty (＠etaash.mathamsetty)]

v4: reset accum on init rather than deinit

[PATCH v11 0/1] MR7806: winewayland: Implement relative motion accumulator - approved

[Alexandros Frantzis (＠afrantzis)]

This merge request was approved by Alexandros Frantzis.

[Alexandros Frantzis (＠afrantzis)]

On Fri Apr 18 16:47:26 2025 +0000, Etaash Mathamsetty wrote:
> Doesn't it resolve the previous race condition, since the accum value
> will get reset on every init?

It makes the race less likely, but it can still happen if we get a destruction and recreation of relative motion while an event handler is running:

1. Thread A: Entering relative motion handler
2. Thread B: Destroys relative motion
3. Thread B: Creates new relative motion (zeroes accum_x/y)
4. Thread A: Relative motion handler (from now destroyed relative motion) continues, updates accum_x/y.

[Alexandros Frantzis (＠afrantzis)]

Thanks!