wayland: Don't modify the mouse capture flag in relative mode

If relative mouse mode is explicitly enabled, don't modify the capture flag on button events or the window might report having lost mouse focus if a button is pressed while moving the cursor.

src/video/wayland/SDL_waylandevents.c

@@ -590,6 +590,7 @@ pointer_handle_button_common(struct SDL_WaylandInput *input, uint32_t serial,
                              uint32_t time, uint32_t button, uint32_t state_w)
 {
     SDL_WindowData *window = input->pointer_focus;
+    SDL_VideoData *viddata = window->waylandData;
     enum wl_pointer_button_state state = state_w;
     uint32_t sdl_button;
 
@@ -628,10 +629,13 @@ pointer_handle_button_common(struct SDL_WaylandInput *input, uint32_t serial,
             input->buttons_pressed &= ~(SDL_BUTTON(sdl_button));
         }
 
-        if (input->buttons_pressed != 0) {
-            window->sdlwindow->flags |= SDL_WINDOW_MOUSE_CAPTURE;
-        } else {
-            window->sdlwindow->flags &= ~SDL_WINDOW_MOUSE_CAPTURE;
+        /* Don't modify the capture flag in relative mode. */
+        if (!viddata->relative_mouse_mode) {
+            if (input->buttons_pressed != 0) {
+                window->sdlwindow->flags |= SDL_WINDOW_MOUSE_CAPTURE;
+            } else {
+                window->sdlwindow->flags &= ~SDL_WINDOW_MOUSE_CAPTURE;
+            }
         }
 
         Wayland_data_device_set_serial(input->data_device, serial);