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fix(server): verify the native display viewport capture without a window resize #22176

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Merged
juliusmarminge merged 1 commit into from
Oct 20, 2026
Merged

fix(server): verify the native display viewport capture without a window resize #22176

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25 changes: 8 additions & 17 deletions apps/server/src/preview/ServerBrowserPage.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -370,9 +370,7 @@ describe("server browser drag", () => {
});
});

// TODO(#19913 follow-up): still flaky in CI after #22154 (Test Server 6 red on most main runs 05:57-06:24Z).
// Skipped again to keep main green; needs a CI-reproducible fix, not another local-only one.
it.skip("captures the native display viewport after page script reassigns the globals", async () => {
it("captures the native display viewport after page script reassigns the globals", async () => {
// Context deviceScaleFactor changes DPR but does not scale raw CDP captures.
const browser = await chromium.launch({
headless: true,
Expand Down Expand Up @@ -410,21 +408,14 @@ it.skip("captures the native display viewport after page script reassigns the gl
zoom: 1,
offset: { x: 0, y: 0 },
});
const { windowId } = await cdp.send("Browser.getWindowForTarget");
// CDP acknowledges the bounds change before the renderer applies it, and a resize event can
// fire for a size on the way there. Page script replaced innerWidth, so read the layout.
const resize = await page.evaluateHandle(`({
done: new Promise(resolve => window.addEventListener("resize", () => {
const { clientWidth, clientHeight } = document.documentElement;
if (clientWidth === 390 && clientHeight === 844) resolve();
})),
})`);
await cdp.send("Browser.setWindowBounds", {
windowId,
bounds: { width: 390, height: 844 },
// Window bounds are ignored by headless Chromium on some hosts; a metrics override resizes
// the page everywhere, and Playwright's viewportSize() stays stale as it would on desktop.
await cdp.send("Emulation.setDeviceMetricsOverride", {
width: 390,
height: 844,
deviceScaleFactor: 0,
mobile: false,
});
await resize.evaluate("resize => resize.done");
await resize.dispose();
expect(await ServerBrowserPage.readPageMetrics(cdp)).toMatchObject({
ratio: 1.5,
width: 390,
Expand Down
33 changes: 1 addition & 32 deletions apps/server/src/preview/ServerBrowserPage.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,6 @@ const MAX_EVALUATION_BYTES = 64_000;
const MAX_VISIBLE_TEXT_LENGTH = 20_000;
const MAX_SCREENSHOT_WIDTH = 1280;
const WAIT_POLL_MS = 100;
const RESIZED_FRAME_MS = 2_000;
export const DIAGNOSTIC_BUFFER_LIMIT = 200;

export class ServerBrowserOperationError extends Error {
Expand Down Expand Up @@ -485,36 +484,6 @@ const renderingOf = async (input: SnapshotInput) => {
};
};

// A desktop window reports a resize before its compositor draws a frame at the new size, so an
// unclipped capture can still return the old frame. Bounded: a frame that never matches is kept.
// Headless pages are sized by the server, which awaits each resize.
const captureResized = async (
input: SnapshotInput,
options: {
readonly scale: number;
readonly viewport: Viewport;
readonly offset: { readonly x: number; readonly y: number } | undefined;
readonly renderScale: number;
},
deadline: number,
) => {
if (input.renderScale !== "display")
return captureViewport(input.page, input.cdp, { format: "png", ...options });
const expected = {
width: options.viewport.width * options.renderScale * options.scale,
height: options.viewport.height * options.renderScale * options.scale,
};
const giveUpAt = Math.min(Date.now() + RESIZED_FRAME_MS, deadline - 2_000);
for (;;) {
const data = await captureViewport(input.page, input.cdp, { format: "png", ...options });
const size = pngSize(data);
const matches =
Math.abs(size.width - expected.width) <= 1 && Math.abs(size.height - expected.height) <= 1;
if (matches || Date.now() + WAIT_POLL_MS >= giveUpAt) return data;
await new Promise((resolve) => setTimeout(resolve, WAIT_POLL_MS));
}
};

const capture = async (
input: SnapshotInput,
deadline: number,
Expand All @@ -537,7 +506,7 @@ const capture = async (
"url" | "title" | "loading" | "visibleText" | "interactiveElements"
>
>,
captureResized(input, { scale, viewport, offset, renderScale }, deadline),
captureViewport(input.page, input.cdp, { format: "png", scale, viewport, offset }),
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]);
void pageAndScreenshot.catch(constVoid);
// Leaves time for the second read; a frame that never loads holds the tree until then.
Expand Down
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