From 06cfea6a03ca3cb58748535d0ab5d70d07ffdc63 Mon Sep 17 00:00:00 2001
From: Frank Praznik <[EMAIL REDACTED]>
Date: Fri, 27 Jun 2025 13:57:38 -0400
Subject: [PATCH] wayland: Improve pointer confinement reliability
If the pointer should be confined, keep trying until a confine/lock signal is received. This considerably improves locking/confinement reliability on compositors where confining can be a racy operation, or may not take effect until the pointer is actually in the confinement region.
A pointer lock is used to special-case 1x1 confinement regions, as otherwise, the pointer can still exhibit jitter at the subpixel level, particularly on scaled desktops.
---
src/video/wayland/SDL_waylandevents.c | 90 ++++++++++++++-----------
src/video/wayland/SDL_waylandevents_c.h | 1 +
src/video/wayland/SDL_waylandmouse.c | 38 ++++++-----
3 files changed, 73 insertions(+), 56 deletions(-)
diff --git a/src/video/wayland/SDL_waylandevents.c b/src/video/wayland/SDL_waylandevents.c
index e0c07e0e4a3ee..d3c305fb7f156 100644
--- a/src/video/wayland/SDL_waylandevents.c
+++ b/src/video/wayland/SDL_waylandevents.c
@@ -592,16 +592,9 @@ static void pointer_dispatch_absolute_motion(SDL_WaylandSeat *seat)
seat->pointer.last_motion.x = (int)SDL_floorf(sx);
seat->pointer.last_motion.y = (int)SDL_floorf(sy);
- /* Pointer confinement regions are created only when the pointer actually enters the region via
- * a motion event received from the compositor.
- */
- if (!SDL_RectEmpty(&window->mouse_rect) && !seat->pointer.confined_pointer) {
- SDL_Rect scaled_mouse_rect;
- Wayland_GetScaledMouseRect(window, &scaled_mouse_rect);
-
- if (SDL_PointInRect(&seat->pointer.last_motion, &scaled_mouse_rect)) {
- Wayland_SeatUpdatePointerGrab(seat);
- }
+ // If the pointer should be confined, but wasn't for some reason, keep trying until it is.
+ if (!SDL_RectEmpty(&window->mouse_rect) && !seat->pointer.is_confined) {
+ Wayland_SeatUpdatePointerGrab(seat);
}
if (window->hit_test) {
@@ -802,7 +795,7 @@ static void pointer_handle_leave(void *data, struct wl_pointer *pointer,
static bool Wayland_ProcessHitTest(SDL_WaylandSeat *seat, Uint32 serial)
{
- // Locked in relative mode, do nothing.
+ // Pointer is immobilized, do nothing.
if (seat->pointer.locked_pointer) {
return false;
}
@@ -1259,14 +1252,16 @@ static const struct zwp_relative_pointer_v1_listener relative_pointer_listener =
relative_pointer_handle_relative_motion,
};
-static void locked_pointer_locked(void *data,
- struct zwp_locked_pointer_v1 *locked_pointer)
+static void locked_pointer_locked(void *data, struct zwp_locked_pointer_v1 *locked_pointer)
{
+ SDL_WaylandSeat *seat = (SDL_WaylandSeat *)data;
+ seat->pointer.is_confined = true;
}
-static void locked_pointer_unlocked(void *data,
- struct zwp_locked_pointer_v1 *locked_pointer)
+static void locked_pointer_unlocked(void *data, struct zwp_locked_pointer_v1 *locked_pointer)
{
+ SDL_WaylandSeat *seat = (SDL_WaylandSeat *)data;
+ seat->pointer.is_confined = false;
}
static const struct zwp_locked_pointer_v1_listener locked_pointer_listener = {
@@ -1274,14 +1269,16 @@ static const struct zwp_locked_pointer_v1_listener locked_pointer_listener = {
locked_pointer_unlocked,
};
-static void confined_pointer_confined(void *data,
- struct zwp_confined_pointer_v1 *confined_pointer)
+static void confined_pointer_confined(void *data, struct zwp_confined_pointer_v1 *confined_pointer)
{
+ SDL_WaylandSeat *seat = (SDL_WaylandSeat *)data;
+ seat->pointer.is_confined = true;
}
-static void confined_pointer_unconfined(void *data,
- struct zwp_confined_pointer_v1 *confined_pointer)
+static void confined_pointer_unconfined(void *data, struct zwp_confined_pointer_v1 *confined_pointer)
{
+ SDL_WaylandSeat *seat = (SDL_WaylandSeat *)data;
+ seat->pointer.is_confined = false;
}
static const struct zwp_confined_pointer_v1_listener confined_pointer_listener = {
@@ -3664,17 +3661,18 @@ void Wayland_SeatUpdatePointerGrab(SDL_WaylandSeat *seat)
SDL_Rect scaled_mouse_rect;
Wayland_GetScaledMouseRect(window, &scaled_mouse_rect);
+ confine_rect = wl_compositor_create_region(display->compositor);
+ wl_region_add(confine_rect,
+ scaled_mouse_rect.x,
+ scaled_mouse_rect.y,
+ scaled_mouse_rect.w,
+ scaled_mouse_rect.h);
+
/* Some compositors will only confine the pointer to an arbitrary region if the pointer
- * is already within the confinement area when it is created.
+ * is already within the confinement area when it is created. Warp the pointer to the
+ * closest point within the confinement zone if outside.
*/
- if (SDL_PointInRect(&seat->pointer.last_motion, &scaled_mouse_rect)) {
- confine_rect = wl_compositor_create_region(display->compositor);
- wl_region_add(confine_rect,
- scaled_mouse_rect.x,
- scaled_mouse_rect.y,
- scaled_mouse_rect.w,
- scaled_mouse_rect.h);
- } else {
+ if (!SDL_PointInRect(&seat->pointer.last_motion, &scaled_mouse_rect)) {
/* Warp the pointer to the closest point within the confinement zone if outside,
* The confinement region will be created when a true position event is received.
*/
@@ -3698,16 +3696,32 @@ void Wayland_SeatUpdatePointerGrab(SDL_WaylandSeat *seat)
}
if (confine_rect || (window->flags & SDL_WINDOW_MOUSE_GRABBED)) {
- seat->pointer.confined_pointer =
- zwp_pointer_constraints_v1_confine_pointer(display->pointer_constraints,
- w->surface,
- seat->pointer.wl_pointer,
- confine_rect,
- ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_PERSISTENT);
- zwp_confined_pointer_v1_add_listener(seat->pointer.confined_pointer,
- &confined_pointer_listener,
- window);
-
+ if (window->mouse_rect.w != 1 && window->mouse_rect.h != 1) {
+ seat->pointer.confined_pointer =
+ zwp_pointer_constraints_v1_confine_pointer(display->pointer_constraints,
+ w->surface,
+ seat->pointer.wl_pointer,
+ confine_rect,
+ ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_PERSISTENT);
+ zwp_confined_pointer_v1_add_listener(seat->pointer.confined_pointer,
+ &confined_pointer_listener,
+ seat);
+ } else {
+ /* Use a lock for 1x1 confinement regions, as the pointer can exhibit subpixel motion otherwise.
+ * A null region is used since the warp *should* have placed the pointer where we want it, but
+ * better to lock it slightly off than let the pointer escape, as confining to a specific region
+ * seems to be a racy operation on some compositors.
+ */
+ seat->pointer.locked_pointer =
+ zwp_pointer_constraints_v1_lock_pointer(display->pointer_constraints,
+ w->surface,
+ seat->pointer.wl_pointer,
+ NULL,
+ ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_PERSISTENT);
+ zwp_locked_pointer_v1_add_listener(seat->pointer.locked_pointer,
+ &locked_pointer_listener,
+ seat);
+ }
if (confine_rect) {
wl_region_destroy(confine_rect);
}
diff --git a/src/video/wayland/SDL_waylandevents_c.h b/src/video/wayland/SDL_waylandevents_c.h
index b30246fa44e9d..8f27ae978f30b 100644
--- a/src/video/wayland/SDL_waylandevents_c.h
+++ b/src/video/wayland/SDL_waylandevents_c.h
@@ -129,6 +129,7 @@ typedef struct SDL_WaylandSeat
Uint32 enter_serial;
SDL_MouseButtonFlags buttons_pressed;
SDL_Point last_motion;
+ bool is_confined;
SDL_MouseID sdl_id;
diff --git a/src/video/wayland/SDL_waylandmouse.c b/src/video/wayland/SDL_waylandmouse.c
index 82a1fdfe0782f..f32124555a1ab 100644
--- a/src/video/wayland/SDL_waylandmouse.c
+++ b/src/video/wayland/SDL_waylandmouse.c
@@ -839,37 +839,39 @@ void Wayland_SeatWarpMouse(SDL_WaylandSeat *seat, SDL_WindowData *window, float
const wl_fixed_t f_y = wl_fixed_from_double(SDL_clamp(y / window->pointer_scale.y, 0, window->current.logical_height));
wp_pointer_warp_v1_warp_pointer(d->wp_pointer_warp_v1, window->surface, seat->pointer.wl_pointer, f_x, f_y, seat->pointer.enter_serial);
} else {
- bool toggle_lock = !seat->pointer.locked_pointer;
bool update_grabs = false;
+ // Pointers can only have one confinement type active on a surface at one time.
+ if (seat->pointer.confined_pointer) {
+ zwp_confined_pointer_v1_destroy(seat->pointer.confined_pointer);
+ seat->pointer.confined_pointer = NULL;
+ update_grabs = true;
+ }
+ if (seat->pointer.locked_pointer) {
+ zwp_locked_pointer_v1_destroy(seat->pointer.locked_pointer);
+ seat->pointer.locked_pointer = NULL;
+ update_grabs = true;
+ }
+
/* The pointer confinement protocol allows setting a hint to warp the pointer,
* but only when the pointer is locked.
*
* Lock the pointer, set the position hint, unlock, and hope for the best.
*/
- if (toggle_lock) {
- if (seat->pointer.confined_pointer) {
- zwp_confined_pointer_v1_destroy(seat->pointer.confined_pointer);
- seat->pointer.confined_pointer = NULL;
- update_grabs = true;
- }
- seat->pointer.locked_pointer = zwp_pointer_constraints_v1_lock_pointer(d->pointer_constraints, window->surface,
- seat->pointer.wl_pointer, NULL,
- ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_ONESHOT);
- }
+ struct zwp_locked_pointer_v1 *warp_lock =
+ zwp_pointer_constraints_v1_lock_pointer(d->pointer_constraints, window->surface,
+ seat->pointer.wl_pointer, NULL,
+ ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_ONESHOT);
const wl_fixed_t f_x = wl_fixed_from_double(x / window->pointer_scale.x);
const wl_fixed_t f_y = wl_fixed_from_double(y / window->pointer_scale.y);
- zwp_locked_pointer_v1_set_cursor_position_hint(seat->pointer.locked_pointer, f_x, f_y);
+ zwp_locked_pointer_v1_set_cursor_position_hint(warp_lock, f_x, f_y);
wl_surface_commit(window->surface);
- if (toggle_lock) {
- zwp_locked_pointer_v1_destroy(seat->pointer.locked_pointer);
- seat->pointer.locked_pointer = NULL;
+ zwp_locked_pointer_v1_destroy(warp_lock);
- if (update_grabs) {
- Wayland_SeatUpdatePointerGrab(seat);
- }
+ if (update_grabs) {
+ Wayland_SeatUpdatePointerGrab(seat);
}
/* NOTE: There is a pending warp event under discussion that should replace this when available.