check screencast parameters

Author: yury-s

docs/src/api/class-inspector.md

@@ -2,7 +2,7 @@
 * since: v1.59
 * langs: js
 
-The `Inspector` object provides access to the Playwright inspector's screencast capabilities, allowing you to capture live JPEG frames from the page as it renders.
+The `Inspector` object provides access to the Playwright inspector's capabilities.
 
 **Usage**
 

packages/playwright-client/types/types.d.ts

@@ -20437,8 +20437,7 @@ export interface FrameLocator {
 }
 
 /**
- * The `Inspector` object provides access to the Playwright inspector's screencast capabilities, allowing you to
- * capture live JPEG frames from the page as it renders.
+ * The `Inspector` object provides access to the Playwright inspector's capabilities.
  *
  * **Usage**
  *

packages/playwright-core/src/server/screencast.ts

@@ -29,6 +29,7 @@ export class Screencast {
   private _videoRecorder: VideoRecorder | null = null;
   private _videoId: string | null = null;
   private _screencastClients = new Set<unknown>();
+  private _screencastOptions: { width: number, height: number, quality: number } | null = null;
 
   // Aiming at 25 fps by default - each frame is 40ms, but we give some slack with 35ms.
   // When throttling for tracing, 200ms between frames, except for 10 frames around the action.
@@ -140,8 +141,13 @@ export class Screencast {
   }
 
   async startScreencast(client: unknown, options: { width: number, height: number, quality: number }) {
+    if (this._screencastOptions) {
+      if (options.width !== this._screencastOptions.width || options.height !== this._screencastOptions.height || options.quality !== this._screencastOptions.quality)
+        throw new Error(`Screencast is already running with different options (${this._screencastOptions.width}x${this._screencastOptions.height} quality=${this._screencastOptions.quality})`);
+    }
     this._screencastClients.add(client);
     if (this._screencastClients.size === 1) {
+      this._screencastOptions = options;
       await this._page.delegate.startScreencast({
         width: options.width,
         height: options.height,
@@ -152,8 +158,10 @@ export class Screencast {
 
   async stopScreencast(client: unknown) {
     this._screencastClients.delete(client);
-    if (!this._screencastClients.size)
+    if (!this._screencastClients.size) {
+      this._screencastOptions = null;
       await this._page.delegate.stopScreencast();
+    }
   }
 }
 

packages/playwright-core/types/types.d.ts

@@ -20437,8 +20437,7 @@ export interface FrameLocator {
 }
 
 /**
- * The `Inspector` object provides access to the Playwright inspector's screencast capabilities, allowing you to
- * capture live JPEG frames from the page as it renders.
+ * The `Inspector` object provides access to the Playwright inspector's capabilities.
  *
  * **Usage**
  *

tests/library/video.spec.ts

@@ -901,7 +901,7 @@ it.describe('screencast', () => {
   it('inspector.startScreencast emits screencastframe events', async ({ browser, server }) => {
     const size = { width: 500, height: 400 };
     const context = await browser.newContext({ viewport: size });
-    const page = await context.newPage(); 
+    const page = await context.newPage();
 
     const frames: Buffer[] = [];
     page.inspector().on('screencastframe', (data: Buffer) => frames.push(data));
@@ -921,6 +921,43 @@ it.describe('screencast', () => {
 
     await context.close();
   });
+
+  it('startScreencast throws when called with different options while running', async ({ browser }) => {
+    const size = { width: 500, height: 400 };
+    const context = await browser.newContext({ viewport: size });
+    const page = await context.newPage();
+
+    await page.inspector().startScreencast({ size });
+    await expect(page.inspector().startScreencast({ size: { width: 320, height: 240 } })).rejects.toThrow('Screencast is already running with different options');
+
+    await page.inspector().stopScreencast();
+    await context.close();
+  });
+
+  it('startScreencast allows restart with different options after stop', async ({ browser }) => {
+    const context = await browser.newContext({ viewport: { width: 500, height: 400 } });
+    const page = await context.newPage();
+
+    await page.inspector().startScreencast({ size: { width: 500, height: 400 } });
+    await page.inspector().stopScreencast();
+    // Different options should succeed once the previous screencast is stopped.
+    await expect(page.inspector().startScreencast({ size: { width: 320, height: 240 } })).resolves.toBeUndefined();
+
+    await page.inspector().stopScreencast();
+    await context.close();
+  });
+
+  it('startScreencast throws when video recording is running with different params', async ({ browser }) => {
+    const videoSize = { width: 500, height: 400 };
+    const context = await browser.newContext({ viewport: videoSize });
+    const page = await context.newPage();
+
+    await page.video().start({ size: videoSize });
+    await expect(page.inspector().startScreencast({ size: { width: 320, height: 240 } })).rejects.toThrow('Screencast is already running with different options');
+
+    await page.video().stop();
+    await context.close();
+  });
 });
 
 it('should saveAs video', async ({ browser }, testInfo) => {