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docs(chromium): tighten paint-polyfill godoc per CONTRIBUTING style [skip ci]

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This commit is contained in:
Julien Neuhart
2026-04-24 12:51:09 +02:00
parent 1c0ff24c4b
commit 05465b3a74
1 changed files with 12 additions and 15 deletions
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pkg/modules/chromium/paint_polyfill.go
+12 -15
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@@ -10,17 +10,15 @@ import (
)
// paintCallbacksPolyfill is a JavaScript shim installed before any user
// script runs. It replaces [requestAnimationFrame], [cancelAnimationFrame],
// [ResizeObserver], and [IntersectionObserver] with timer-backed
// implementations. Headless Chromium's print-emulation pipeline does not
// tick the compositor refresh driver reliably between
// "load" and [Page.printToPDF], which leaves the native rAF /
// ResizeObserver / IntersectionObserver queues permanently stalled and
// breaks charting libraries (visx, ApexCharts, and similar) that rely on
// rAF-gated measurement. The polyfill exposes the same APIs with timer
// semantics, so user scripts that schedule work on those callbacks
// receive their measurements and Gotenberg's rendered output reflects
// the page the author intended. See
// script runs. Replaces requestAnimationFrame, cancelAnimationFrame,
// ResizeObserver, and IntersectionObserver with timer-backed
// implementations. Headless Chromium's print-emulation pipeline does
// not tick the compositor refresh driver between the load event and
// the Page.printToPDF call, which leaves the native callback queues
// stalled and breaks charting libraries (visx, ApexCharts) that rely
// on rAF-gated measurement. The polyfill exposes the same APIs with
// timer semantics so user-scheduled callbacks fire in print mode and
// the rendered output matches a live browser. See
// https://github.com/gotenberg/gotenberg/issues/1535.
const paintCallbacksPolyfill = `
(function () {
@@ -126,10 +124,9 @@ const paintCallbacksPolyfill = `
// injectPaintCallbacksPolyfillActionFunc installs the
// [paintCallbacksPolyfill] via [page.AddScriptToEvaluateOnNewDocument]
// so that it runs before any user script on the navigated page. Callers
// set install=false to skip the shim when no readiness signal gates the
// conversion, which preserves the native implementations for pages that
// do not require it.
// so that it runs before any user script on the navigated page. When
// install is false the action is a no-op and the page keeps the native
// rAF, ResizeObserver, and IntersectionObserver implementations.
func injectPaintCallbacksPolyfillActionFunc(logger *slog.Logger, install bool) chromedp.ActionFunc {
return func(ctx context.Context) error {
if !install {