Hi team,

I am using the latest PhantomJS project, which uses QT Webkit 5.3.1.

There seems to be a bug when querying the natural width and natural height of an SVG image when the <img> node has a CSS-defined width/height. This URL is a live test example:

http://staticpages.diffbot.com/smoketest/2943/index_svg.html

Basically, WebKit thinks the natural width/height of the SVG image is always the width/height of its container, when its not always the case. In this test page, an <img> node points to an external 48x48 SVG image resource, so its natural width/height should be 48 pixels. However, since the <img> was stylized with width:100%, WebKit thinks the natural width of the SVG image is 800+ pixels.

I don't know SVG documents that well, but believe the part of code that can fix this is in SVGImageCache.cpp. Here is the original source:

IntSize SVGImageCache::imageSizeForRenderer(const RenderObject* renderer) const
{
    IntSize imageSize = m_svgImage->size();
    if (!renderer)
        return imageSize;

    ImageForContainerMap::const_iterator it = m_imageForContainerMap.find(renderer);
    if (it == m_imageForContainerMap.end())
        return imageSize;

    RefPtr<SVGImageForContainer> imageForContainer = it->value;
    ASSERT(!imageForContainer->size().isEmpty());
    return imageForContainer->size();
}

This function always gets the size of the container of the SVG image (if it exists), rather than the size of the image itself. I believe it should first check of the SVG image is just an external image file loaded by an <img> node. If it is just an external image file, then it should just return the size of the image itself; however, if it is created by an SVG document, then it should return the size of its container. Here is my modified code that I compiled and tested on the live test URL (as well as random URLs), and it seems to fix the bug without introducing any new bugs:

IntSize SVGImageCache::imageSizeForRenderer(const RenderObject* renderer) const
{
    IntSize imageSize = m_svgImage->size();
    if (!renderer)
        return imageSize;
    if (renderer->resourceClientType() != CachedResourceClient::SVGDocumentType)
        return imageSize;

    ImageForContainerMap::const_iterator it = m_imageForContainerMap.find(renderer);
    if (it == m_imageForContainerMap.end())
        return imageSize;

    RefPtr<SVGImageForContainer> imageForContainer = it->value;
    ASSERT(!imageForContainer->size().isEmpty());
    return imageForContainer->size();
}

I simply added a check if the resourceClientType is an SVG Document – if it s not of type SVG Document, then it is probably an external image resource, so it returns imageSize.

If there is a better solution, please keep me updated on this ticket. Would love to see how this bug can be fixed, and I'll help contribute to the project any way I can.

Thanks!

Best,
Kevin