Bug 280350 – [SVG2] Sync `getTotalLength()` with web specification to throw exception when non-renderable

• Status: REOPENED
• Component: SVG

[Ahmad Saleem]

Hi Team,

While looking into failing WPT test case, I stumbled upon another mismatch in web-spec alignment:

Web Spec: https://svgwg.org/svg2-draft/types.html#__svg__SVGGeometryElement__getTotalLength

"If current element is a non-rendered element, and the UA is not able to compute the total length of the path, then throw an InvalidStateError."

So when I look into our code, we return `0` rather than Exception.


WebKit Code: https://github.com/WebKit/WebKit/blob/3c1c55324a3609e8dab5bc4b4bacac0d58cde486/Source/WebCore/svg/SVGGeometryElement.cpp#L49 & https://github.com/WebKit/WebKit/blob/3c1c55324a3609e8dab5bc4b4bacac0d58cde486/Source/WebCore/svg/SVGPathElement.cpp#L181

^ We need to update definitions in `.h` as well.

Changing them to `ExceptionOr<float>` and then return `InvalidStateError`.

__

Code:

ExceptionOr<float> SVGGeometryElement::getTotalLength() const
{
    protectedDocument()->updateLayoutIgnorePendingStylesheets({ LayoutOptions::ContentVisibilityForceLayout }, this);

    auto* renderer = this->renderer();
    if (!renderer)
        return Exception { ExceptionCode::InvalidStateError };

    if (CheckedPtr renderSVGShape = dynamicDowncast<LegacyRenderSVGShape>(renderer))
        return renderSVGShape->getTotalLength();

    if (CheckedPtr renderSVGShape = dynamicDowncast<RenderSVGShape>(renderer))
        return renderSVGShape->getTotalLength();

    ASSERT_NOT_REACHED();
    return Exception { ExceptionCode::InvalidStateError };
}

and call-site in `getPointAtLength`:

// Spec: Clamp distance to [0, length].
    auto totalLength =  getTotalLength();
    if (totalLength.hasException())
        return totalLength.releaseException();
    distance = clampTo<float>(distance, 0, totalLength.releaseReturnValue());

while in SVGPathElement.cpp:

ExceptionOr<float> SVGPathElement::getTotalLength() const
{
    protectedDocument()->updateLayoutIgnorePendingStylesheets({ LayoutOptions::ContentVisibilityForceLayout }, this);

    if (pathByteStream().isEmpty())
        return Exception { ExceptionCode::InvalidStateError, "The element's path is empty."_s };

    return getTotalLengthOfSVGPathByteStream(pathByteStream());
}

and same on call-site.

___

Test Case (from Blink) - https://jsfiddle.net/3zwLk15h/ (We pass now - Firefox is not following spec here as well and fails this).

Thanks!

[Radar WebKit Bug Importer]

<rdar://problem/136719548>

[Ahmad Saleem]

Pull request: https://github.com/WebKit/WebKit/pull/34273

[EWS]

Committed 284311@main (48ed528d4e27): <https://commits.webkit.org/284311@main>

Reviewed commits have been landed. Closing PR #34273 and removing active labels.

[WebKit Commit Bot]

Re-opened since this is blocked by bug 282343

[Ahmad Saleem]

NOTE: Take feedback from this PR (thanks to Said) - https://github.com/WebKit/WebKit/pull/35873