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miguel-heygenmiguel-heygen
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fix(engine): stop SwiftShader ghosting in software screenshot captures (#3096)
Apply the --disable-gpu-compositing workaround to every software capture, not just BeginFrame ones. SwiftShader's compositor re-presents stale raster for a partially invalidated layer, so successive screenshot captures accumulate copies of earlier seeks; alpha renders are forced onto the screenshot path and were the only ones left unprotected. Refreshes the byte-strict png-sequence alpha baseline for the resulting antialiasing delta (content unchanged, min PSNR 41.3 dB). Fixes #3049.
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Lines changed: 162 additions & 148 deletions

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‎packages/engine/src/services/browserManager.test.ts‎

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Original file line numberDiff line numberDiff line change
@@ -7,6 +7,8 @@ import { join } from "node:path";
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import type { Browser, PuppeteerNode } from "puppeteer-core";
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import type { CaptureMode } from "./browserLeasePool.js";
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import {
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_resetAutoBrowserGpuModeCacheForTests,
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_resetBrowserPoolForTests,
@@ -132,23 +134,22 @@ describe("buildChromeArgs browser GPU mode", () => {
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expect(args).not.toContain("--enable-gpu-rasterization");
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});
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it("disables GPU compositing only for software BeginFrame capture", () => {
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const softwareBeginFrame = buildChromeArgs(
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{ ...base, captureMode: "beginframe" },
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{ browserGpuMode: "software" },
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);
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const softwareScreenshot = buildChromeArgs(
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{ ...base, captureMode: "screenshot" },
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{ browserGpuMode: "software" },
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);
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const hardwareBeginFrame = buildChromeArgs(
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{ ...base, captureMode: "beginframe", platform: "linux" },
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{ browserGpuMode: "hardware" },
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);
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// HF#3049: the stale-raster accumulation lives in SwiftShader's compositor,
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// which every capture mode reads from — so the gate is the GPU mode alone.
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// Swept over the whole CaptureMode union so a future mode can't quietly opt
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// out of the workaround the way `screenshot` did.
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const captureModes: CaptureMode[] = ["beginframe", "screenshot", "drawelement"];
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it.each(captureModes)("disables GPU compositing for software %s capture", (captureMode) => {
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expect(
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buildChromeArgs({ ...base, captureMode, platform: "linux" }, { browserGpuMode: "software" }),
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).toContain("--disable-gpu-compositing");
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});
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expect(softwareBeginFrame).toContain("--disable-gpu-compositing");
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expect(softwareScreenshot).not.toContain("--disable-gpu-compositing");
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expect(hardwareBeginFrame).not.toContain("--disable-gpu-compositing");
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it.each(captureModes)("leaves hardware %s capture on the GPU compositor", (captureMode) => {
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expect(
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buildChromeArgs({ ...base, captureMode, platform: "linux" }, { browserGpuMode: "hardware" }),
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).not.toContain("--disable-gpu-compositing");
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});
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it("uses Metal-backed ANGLE for hardware browser GPU mode on macOS", () => {

‎packages/engine/src/services/browserManager.ts‎

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Original file line numberDiff line numberDiff line change
@@ -910,20 +910,33 @@ export function buildChromeArgs(
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chromeArgs.push(WEBGPU_FLAG);
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}
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// SwiftShader's GPU compositor can retain a transformed layer for several
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// sequential frames after a GSAP yoyo/reversal, and it re-presents stale
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// raster for a partially invalidated layer: content already drawn in an
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// earlier seek is never cleared, so successive captures accumulate copies of
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// it (HF#3049 — a moving SVG group smears wider on every frame, and static
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// siblings appear duplicated one band lower). The DOM and timeline are
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// already at the requested time; the defect is in the compositor surface both
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// BeginFrame and Page.captureScreenshot read, so it is not specific to a
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// capture mode — it is specific to compositing on SwiftShader.
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//
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// Routing compositing through Chrome's software path is the only mitigation
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// that holds: capture-side changes (fromSurface, captureBeyondViewport, a
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// second capture, extra rAF ticks, a 250ms settle) and every raster/tiling
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// flag (--disable-partial-raster, --disable-checker-imaging, --disable-zero-copy,
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// forced tile sizes) leave the accumulation untouched. The cost is that
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// SwiftShader rasterizes thin strokes and glyph edges slightly differently
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// (antialiased edges only — measured on HF#3049's frame 0: 96 opaque pixels
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// differ, by 1/255). Duplicated content in 68% of frames is the worse defect.
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//
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// Remove this workaround once the pinned chrome-headless-shell includes
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// https://issues.chromium.org/issues/535256667.
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if (browserGpuMode === "software") {
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chromeArgs.push("--disable-gpu-compositing");
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}
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// BeginFrame flags — only when using chrome-headless-shell on Linux
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if (options.captureMode !== "screenshot") {
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// SwiftShader's GPU compositor can retain a transformed layer for several
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// sequential frames after a GSAP yoyo/reversal. The DOM and timeline are
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// already at the requested time, but both BeginFrame and
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// Page.captureScreenshot read the stale surface (the duplicate is present
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// in the raw JPEG before encoding). Keep deterministic BeginFrame capture,
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// but route compositing through Chrome's software path when the browser is
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// already in software-GPU mode. Hardware-GPU and screenshot captures keep
922-
// their existing compositor paths. Remove this workaround once the pinned
923-
// chrome-headless-shell includes https://issues.chromium.org/issues/535256667.
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if (browserGpuMode === "software") {
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chromeArgs.push("--disable-gpu-compositing");
926-
}
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chromeArgs.push(
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"--deterministic-mode",
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"--enable-begin-frame-control",

‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000001.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000002.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000003.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000004.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000005.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000006.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000007.png‎

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‎packages/producer/tests/distributed/png-sequence/output/frames/frame_000008.png‎

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