feat(mpv): add opaque subtitle background with adjustable opacity (iOS only)

modules/mpv-player/ios/MPVLayerRenderer.swift

@@ -195,7 +195,8 @@ final class MPVLayerRenderer {
         // CRITICAL: This option MUST be set immediately after vo=avfoundation, before hwdec options.
         // On tvOS, moving this elsewhere causes the app to freeze when exiting the player.
         // - iOS: "yes" for PiP subtitle support (subtitles baked into video)
-        // - tvOS: "no" to prevent gray tint + frame drops with subtitles
+        // - tvOS: "no" - composite OSD breaks subtitle rendering entirely on tvOS
+        //         Note: This means subtitle styling (background colors) won't work on tvOS
         #if os(tvOS)
         checkError(mpv_set_option_string(handle, "avfoundation-composite-osd", "no"))
         #else
@@ -820,7 +821,22 @@ final class MPVLayerRenderer {
     func setSubtitleFontSize(_ size: Int) {
         setProperty(name: "sub-font-size", value: String(size))
     }
-    
+
+    func setSubtitleBackgroundColor(_ color: String) {
+        setProperty(name: "sub-back-color", value: color)
+    }
+
+    func setSubtitleBorderStyle(_ style: String) {
+        // "outline-and-shadow" (default) or "background-box" (enables background color)
+        setProperty(name: "sub-border-style", value: style)
+    }
+
+    func setSubtitleAssOverride(_ mode: String) {
+        // Controls whether to override ASS subtitle styles
+        // "no" = keep ASS styles, "force" = override with user settings
+        setProperty(name: "sub-ass-override", value: mode)
+    }
+
     // MARK: - Audio Track Controls
     
     func getAudioTracks() -> [[String: Any]] {

modules/mpv-player/ios/MpvPlayerModule.swift

@@ -157,7 +157,19 @@ public class MpvPlayerModule: Module {
       AsyncFunction("setSubtitleFontSize") { (view: MpvPlayerView, size: Int) in
         view.setSubtitleFontSize(size)
       }
-      
+
+      AsyncFunction("setSubtitleBackgroundColor") { (view: MpvPlayerView, color: String) in
+        view.setSubtitleBackgroundColor(color)
+      }
+
+      AsyncFunction("setSubtitleBorderStyle") { (view: MpvPlayerView, style: String) in
+        view.setSubtitleBorderStyle(style)
+      }
+
+      AsyncFunction("setSubtitleAssOverride") { (view: MpvPlayerView, mode: String) in
+        view.setSubtitleAssOverride(mode)
+      }
+
       // Audio track functions
       AsyncFunction("getAudioTracks") { (view: MpvPlayerView) -> [[String: Any]] in
         return view.getAudioTracks()

modules/mpv-player/ios/MpvPlayerView.swift

@@ -319,6 +319,18 @@ class MpvPlayerView: ExpoView {
 		renderer?.setSubtitleFontSize(size)
 	}
 
+	func setSubtitleBackgroundColor(_ color: String) {
+		renderer?.setSubtitleBackgroundColor(color)
+	}
+
+	func setSubtitleBorderStyle(_ style: String) {
+		renderer?.setSubtitleBorderStyle(style)
+	}
+
+	func setSubtitleAssOverride(_ mode: String) {
+		renderer?.setSubtitleAssOverride(mode)
+	}
+
 	// MARK: - Video Scaling
 
 	func setZoomedToFill(_ zoomed: Bool) {

modules/mpv-player/src/MpvPlayer.types.ts

@@ -95,6 +95,11 @@ export interface MpvPlayerViewRef {
   setSubtitleAlignX: (alignment: "left" | "center" | "right") => Promise<void>;
   setSubtitleAlignY: (alignment: "top" | "center" | "bottom") => Promise<void>;
   setSubtitleFontSize: (size: number) => Promise<void>;
+  setSubtitleBackgroundColor: (color: string) => Promise<void>;
+  setSubtitleBorderStyle: (
+    style: "outline-and-shadow" | "background-box",
+  ) => Promise<void>;
+  setSubtitleAssOverride: (mode: "no" | "force") => Promise<void>;
   // Audio controls
   getAudioTracks: () => Promise<AudioTrack[]>;
   setAudioTrack: (trackId: number) => Promise<void>;

modules/mpv-player/src/MpvPlayerView.tsx

@@ -84,6 +84,17 @@ export default React.forwardRef<MpvPlayerViewRef, MpvPlayerViewProps>(
       setSubtitleFontSize: async (size: number) => {
         await nativeRef.current?.setSubtitleFontSize(size);
       },
+      setSubtitleBackgroundColor: async (color: string) => {
+        await nativeRef.current?.setSubtitleBackgroundColor(color);
+      },
+      setSubtitleBorderStyle: async (
+        style: "outline-and-shadow" | "background-box",
+      ) => {
+        await nativeRef.current?.setSubtitleBorderStyle(style);
+      },
+      setSubtitleAssOverride: async (mode: "no" | "force") => {
+        await nativeRef.current?.setSubtitleAssOverride(mode);
+      },
       // Audio controls
       getAudioTracks: async () => {
         return await nativeRef.current?.getAudioTracks();