Work around mouse capture SDL bug on macOS

On macOS, SDL relative mouse mode does not work correctly when the
cursor is outside the window.

As a workaround, move the cursor inside the window before setting the
relative mouse mode.

Refs <libsdl-org/SDL#5340>

app/src/screen.c

@@ -164,7 +164,26 @@ sc_screen_is_relative_mode(struct sc_screen *screen) {
 
 static void
 sc_screen_set_mouse_capture(struct sc_screen *screen, bool capture) {
+#ifdef __APPLE__
+    // Workaround for SDL bug on macOS:
+    // <https://github.com/libsdl-org/SDL/issues/5340>
+    if (capture) {
+        int mouse_x, mouse_y;
+        SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+
+        int x, y, w, h;
+        SDL_GetWindowPosition(screen->window, &x, &y);
+        SDL_GetWindowSize(screen->window, &w, &h);
+
+        bool outside_window = mouse_x < x || mouse_x >= x + w
+                           || mouse_y < y || mouse_y >= y + h;
+        if (outside_window) {
+            SDL_WarpMouseInWindow(screen->window, w / 2, h / 2);
+        }
+    }
+#else
     (void) screen;
+#endif
     if (SDL_SetRelativeMouseMode(capture)) {
         LOGE("Could not set relative mouse mode to %s: %s",
              capture ? "true" : "false", SDL_GetError());

app/src/usb/screen_otg.c

@@ -6,7 +6,26 @@
 
 static void
 sc_screen_otg_set_mouse_capture(struct sc_screen_otg *screen, bool capture) {
+#ifdef __APPLE__
+    // Workaround for SDL bug on macOS:
+    // <https://github.com/libsdl-org/SDL/issues/5340>
+    if (capture) {
+        int mouse_x, mouse_y;
+        SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+
+        int x, y, w, h;
+        SDL_GetWindowPosition(screen->window, &x, &y);
+        SDL_GetWindowSize(screen->window, &w, &h);
+
+        bool outside_window = mouse_x < x || mouse_x >= x + w
+                           || mouse_y < y || mouse_y >= y + h;
+        if (outside_window) {
+            SDL_WarpMouseInWindow(screen->window, w / 2, h / 2);
+        }
+    }
+#else
     (void) screen;
+#endif
     if (SDL_SetRelativeMouseMode(capture)) {
         LOGE("Could not set relative mouse mode to %s: %s",
              capture ? "true" : "false", SDL_GetError());