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) {