Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 80df4def20e353fcac0db435bb69dcec20f8c4b3
https://github.com/WebKit/WebKit/commit/80df4def20e353fcac0db435bb69dcec20f8c4b3
Author: Ahmad Saleem <[email protected]>
Date: 2026-08-20 (Thu, 20 Aug 2026)
Changed paths:
M Source/WebCore/html/HTMLCanvasElement.idl
Log Message:
-----------
Align HTMLCanvasElement interface with HTML spec for toDataURL() and toBlob()
https://bugs.webkit.org/show_bug.cgi?id=322163
rdar://185391614
Reviewed by Ryosuke Niwa.
Bring the IDL for HTMLCanvasElement.toDataURL() and toBlob() in line with
https://html.spec.whatwg.org/multipage/canvas.html#htmlcanvaselement:
USVString toDataURL(optional DOMString type = "image/png", optional any
quality);
undefined toBlob(BlobCallback callback, optional DOMString type =
"image/png", optional any quality);
Both changes are no-ops at the JS boundary, so there is nothing new to test:
1. toDataURL()'s return type becomes USVString. The implementation returns an
UncachedString, and JSConverter<IDLUSVString>::convert(const UncachedString&)
is identical to the IDLDOMString overload -- both are jsString(vm,
value.string)
-- so the generated binding is unchanged. USVString on a return type is a
declarative claim that the value contains no unpaired surrogates, which is
trivially true of a base64 data URL. The distinction only has teeth in the
JS-to-native direction, where valueToUSVString() substitutes U+FFFD.
2. Defaulting `type` to "image/png" changes
convertOptionalWithDefault<IDLDOMString>
to hand the implementation "image/png" instead of a null String when the
argument is omitted or undefined. The parameter's only consumer in either
function is toEncodingMimeType(), which already maps both inputs to the same
result: a null String is rejected by
MIMETypeRegistry::isSupportedImageMIMETypeForEncoding()
on its isEmpty() check and falls back to "image/png", while "image/png" is
supported and returns its own ASCII-lowercased self. This also makes
HTMLCanvasElement consistent with ImageEncodeOptions.type in
OffscreenCanvas.idl,
which already carries the same default.
Also add the spec URL to the top of the file, matching the convention used by
the
other IDL files in this directory.
* Source/WebCore/html/HTMLCanvasElement.idl:
Canonical link: https://commits.webkit.org/319529@main
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