cursor: rate-limit resize events respecting monitor's refresh rate

This fixes the lag when resizing windows of some apps on XWayland
(e.g. Chromium and Steam).

diff --git a/src/input/cursor.c b/src/input/cursor.c
index e5a214b70b597a37df132cc90f4ba372ec554750..4c0015d3d8b85bc87fc575f67c0c017c07cbeebe 100644 (file)
--- a/src/input/cursor.c
+++ b/src/input/cursor.c
@@ -248,6 +248,28 @@ process_cursor_move(struct server *server, uint32_t time)
 static void
 process_cursor_resize(struct server *server, uint32_t time)
 {
+       /* Rate-limit resize events respecting monitor refresh rate */
+       static uint32_t last_resize_time = 0;
+       static struct view *last_resize_view = NULL;
+
+       if (server->grabbed_view == last_resize_view) {
+               int32_t refresh = 0;
+               if (output_is_usable(last_resize_view->output)) {
+                       refresh = last_resize_view->output->wlr_output->refresh;
+               }
+               /* Limit to 250Hz if refresh rate is not available */
+               if (refresh <= 0) {
+                       refresh = 250000;
+               }
+               /* Not caring overflow, but it won't be observable */
+               if (time - last_resize_time < 1000000 / (uint32_t)refresh) {
+                       return;
+               }
+       }
+
+       last_resize_time = time;
+       last_resize_view = server->grabbed_view;
+
        double dx = server->seat.cursor->x - server->grab_x;
        double dy = server->seat.cursor->y - server->grab_y;