Fix ctrl-s (screenshot window) does not work, #4822

This commit will change the MPVController.mpvInitRendering method to
enable advanced control when creating the mpv renderer context. Advanced
control must be enabled for this variation of the screenshot command to
work.

iina/MPVController.swift

@@ -462,6 +462,12 @@ not applying FFmpeg 9599 workaround
     mpvVersion = getString(MPVProperty.mpvVersion)
   }
 
+  /// Initialize the `mpv` renderer.
+  ///
+  /// This method creates and initializes the `mpv` renderer and sets the callback that `mpv` calls when a new video frame is available.
+  ///
+  /// - Note: Advanced control must be enabled for the screenshot command to work when the window flag is used. See issue
+  ///         [#4822](https://github.com/iina/iina/issues/4822) for details.
   func mpvInitRendering() {
     guard let mpv = mpv else {
       fatalError("mpvInitRendering() should be called after mpv handle being initialized!")
@@ -470,14 +476,16 @@ not applying FFmpeg 9599 workaround
     var openGLInitParams = mpv_opengl_init_params(get_proc_address: mpvGetOpenGLFunc,
                                                   get_proc_address_ctx: nil)
     withUnsafeMutablePointer(to: &openGLInitParams) { openGLInitParams in
-      // var advanced: CInt = 1
-      var params = [
-        mpv_render_param(type: MPV_RENDER_PARAM_API_TYPE, data: apiType),
-        mpv_render_param(type: MPV_RENDER_PARAM_OPENGL_INIT_PARAMS, data: openGLInitParams),
-        // mpv_render_param(type: MPV_RENDER_PARAM_ADVANCED_CONTROL, data: &advanced),
-        mpv_render_param()
-      ]
-      mpv_render_context_create(&mpvRenderContext, mpv, &params)
+      var advanced: CInt = 1
+      withUnsafeMutablePointer(to: &advanced) { advanced in
+        var params = [
+          mpv_render_param(type: MPV_RENDER_PARAM_API_TYPE, data: apiType),
+          mpv_render_param(type: MPV_RENDER_PARAM_OPENGL_INIT_PARAMS, data: openGLInitParams),
+          mpv_render_param(type: MPV_RENDER_PARAM_ADVANCED_CONTROL, data: advanced),
+          mpv_render_param()
+        ]
+        mpv_render_context_create(&mpvRenderContext, mpv, &params)
+      }
       openGLContext = CGLGetCurrentContext()
       mpv_render_context_set_update_callback(mpvRenderContext!, mpvUpdateCallback, mutableRawPointerOf(obj: player.mainWindow.videoView.videoLayer))
     }