feat(decoder): add an option to enable capture WebGL canvas

libraries/scrcpy-decoder-webcodecs/src/index.ts

@@ -81,13 +81,23 @@ export class WebCodecsVideoDecoder implements ScrcpyVideoDecoder {
     #currentFrameRendered = false;
     #animationFrameId = 0;
 
-    constructor(codec: ScrcpyVideoCodecId) {
+    /**
+     * Create a new WebCodecs video decoder.
+     * @param codec The video codec to decode
+     * @param enableCapture
+     * Whether to allow capturing the canvas content using APIs like `readPixels` and `toDataURL`.
+     * Enable this option may reduce performance.
+     */
+    constructor(codec: ScrcpyVideoCodecId, enableCapture: boolean) {
         this.#codec = codec;
 
         this.#canvas = document.createElement("canvas");
 
         try {
-            this.#renderer = new WebGLFrameRenderer(this.#canvas);
+            this.#renderer = new WebGLFrameRenderer(
+                this.#canvas,
+                enableCapture,
+            );
         } catch {
             this.#renderer = new BitmapFrameRenderer(this.#canvas);
         }

libraries/scrcpy-decoder-webcodecs/src/webgl.ts

@@ -26,15 +26,24 @@ void main(void) {
 
     #context: WebGLRenderingContext;
 
-    constructor(canvas: HTMLCanvasElement) {
+    /**
+     * Create a new WebGL frame renderer.
+     * @param canvas The canvas to render frames to.
+     * @param enableCapture
+     * Whether to allow capturing the canvas content using APIs like `readPixels` and `toDataURL`.
+     * Enable this option may reduce performance.
+     */
+    constructor(canvas: HTMLCanvasElement, enableCapture: boolean) {
         const gl =
             canvas.getContext("webgl2", {
                 alpha: false,
                 failIfMajorPerformanceCaveat: true,
+                preserveDrawingBuffer: enableCapture,
             }) ||
             canvas.getContext("webgl", {
                 alpha: false,
                 failIfMajorPerformanceCaveat: true,
+                preserveDrawingBuffer: enableCapture,
             });
         if (!gl) {
             throw new Error("WebGL not supported");