html: remove overlay on html2canvas errors; add cleanup test; optional colorSpaceFallback='srgb' for inline color(display-p3 …)

[chethanac15]

Summary

• Ensures the HTML plugin always removes its overlay when html2canvas throws, so the page doesn’t get stuck behind a non-interactive overlay.
• Adds a test that verifies overlay cleanup on error.
• Introduces an optional, opt-in fallback to convert inline CSS Color 4 values like color(display-p3 …) to approximate sRGB rgb/rgba before rendering.

What changed

• src/modules/html.js

  • Worker.prototype.toCanvas() and Worker.prototype.toContext2d()
    • On success and in .catch(...), safely remove .html2pdf__overlay if present and null it.
  • New helpers
    • replaceDisplayP3InStyle(styleText): rewrites color(display-p3 …) → rgb/rgba (lossy).
    • applyColorFallbackInlineStyles(root): walks the cloned subtree and updates inline style attributes.
  • toContainer()
    • If options.colorSpaceFallback === 'srgb', apply the inline-style fallback to the cloned source before rendering.

• test/specs/html.spec.js

  • New test: “removes overlay when html2canvas throws an error.”
    • Stubs window.html2canvas to reject, asserts error propagation and overlay removal.

• types/index.d.ts

  • HTMLOptions: adds colorSpaceFallback?: 'srgb' | 'none'.

• README.md

  • “HTML rendering notes” section with usage and limitations for colorSpaceFallback.

Usage (optional fallback)

import { jsPDF } from 'jspdf';

const doc = new jsPDF();
await doc.html(elementOrHtmlString, {
  // Converts inline style attributes with color(display-p3 ...) to rgb()/rgba() before rendering
  colorSpaceFallback: 'srgb'
});

Notes and limitations

• The fallback is optional and off by default. It only transforms inline style attributes of the provided subtree.
• External stylesheets and general computed styles are not changed.
• Conversion to sRGB is approximate and lossy by design.
• Full CSS Color 4 Display‑P3 support depends on upstream html2canvas (e.g., Error: Attempting to parse an unsupported color function "color" niklasvh/html2canvas#2700).

Testing

• Full test suite passes locally (pre-existing pending specs unchanged).
• New test covers overlay cleanup on html2canvas rejection.

Housekeeping

• Excludes dist/ artifacts from the PR (reset to upstream).

Related

• Partially addresses html: color(display-p3 ...) support #3856
  • Fully fixes the “overlay left after crash” aspect.
  • Provides an optional, inline-only mitigation for color(display-p3 …) until upstream support lands.

Checklist

• Overlay is removed on success and error paths in html() rendering
• Added test for overlay cleanup on error
• Optional inline color fallback behind colorSpaceFallback: 'srgb'
• Types updated (HTMLOptions)
• Docs updated (README)
• No dist/ artifacts included in the PR