feat: hide blinking cursor when making screenshots (#11854)

References #9938

packages/playwright-core/src/server/chromium/crDragDrop.ts

@@ -84,6 +84,7 @@ export class DragManager {
           const val = await didStartDrag;
           window.removeEventListener('mousemove', mouseListener, { capture: true });
           window.removeEventListener('dragstart', dragListener, { capture: true });
+          delete window.__cleanupDrag;
           return val;
         };
       }).toString(), true, 'utility').catch(() => {});

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

@@ -22,6 +22,12 @@ import * as types from './types';
 import { Progress } from './progress';
 import { assert } from '../utils/utils';
 
+declare global {
+  interface Window {
+    __cleanupScreenshot?: () => void;
+  }
+}
+
 export class Screenshotter {
   private _queue = new TaskQueue();
   private _page: Page;
@@ -115,8 +121,36 @@ export class Screenshotter {
       progress.cleanupWhenAborted(() => this._page._delegate.setBackgroundColor());
     }
     progress.throwIfAborted(); // Avoid extra work.
+
+    const restoreBlinkingCaret = async () => {
+      await Promise.all(this._page.frames().map(async frame => {
+        frame.nonStallingEvaluateInExistingContext('window.__cleanupScreenshot && window.__cleanupScreenshot()', false, 'utility').catch(() => {});
+      }));
+    };
+    await Promise.all(this._page.frames().map(async frame => {
+      await frame.nonStallingEvaluateInExistingContext((function() {
+        const styleTag = document.createElement('style');
+        styleTag.textContent = `
+          * { caret-color: transparent !important; }
+          * > * { caret-color: transparent !important; }
+          * > * > * { caret-color: transparent !important; }
+          * > * > * > * { caret-color: transparent !important; }
+          * > * > * > * > * { caret-color: transparent !important; }
+        `;
+        document.documentElement.append(styleTag);
+        window.__cleanupScreenshot = () => {
+          styleTag.remove();
+          delete window.__cleanupScreenshot;
+        };
+      }).toString(), true, 'utility').catch(() => {});
+    }));
+    progress.cleanupWhenAborted(() => restoreBlinkingCaret());
+    progress.throwIfAborted(); // Avoid extra work.
+
     const buffer = await this._page._delegate.takeScreenshot(progress, format, documentRect, viewportRect, options.quality, fitsViewport);
     progress.throwIfAborted(); // Avoid restoring after failure - should be done by cleanup.
+    await restoreBlinkingCaret();
+    progress.throwIfAborted(); // Avoid restoring after failure - should be done by cleanup.
     if (shouldSetDefaultBackground)
       await this._page._delegate.setBackgroundColor();
     progress.throwIfAborted(); // Avoid side effects.

tests/page/page-screenshot.spec.ts

@@ -31,6 +31,23 @@ it.describe('page screenshot', () => {
     expect(screenshot).toMatchSnapshot('screenshot-sanity.png');
   });
 
+  it('should not capture blinking caret', async ({ page, server }) => {
+    await page.setContent(`
+      <div contenteditable="true"></div>
+    `);
+    const div = page.locator('div');
+    await div.type('foo bar');
+    const screenshot = await div.screenshot();
+    for (let i = 0; i < 10; ++i) {
+      // Caret blinking time is set to 500ms.
+      // Try to capture variety of screenshots to make
+      // sure we don't capture blinking caret.
+      await new Promise(x => setTimeout(x, 150));
+      const newScreenshot = await div.screenshot();
+      expect(newScreenshot.equals(screenshot)).toBe(true);
+    }
+  });
+
   it('should clip rect', async ({ page, server }) => {
     await page.setViewportSize({ width: 500, height: 500 });
     await page.goto(server.PREFIX + '/grid.html');