[Webkit-unassigned] [Bug 15443] SVGImage does not support sub-resource loading

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=15443





--- Comment #19 from Nikolas Zimmermann <zimmermann at kde.org>  2011-02-09 09:17:29 PST ---
(In reply to comment #16)
> Adam Barth explained to me some a list of issues (which he believes to be SVG design errors) that affect the SVG <image> tag.
> 
> The <image> tag is good to be used with raster graphics, but not so much with SVG graphics, because it loses both semantics and performance during rasterization. The <use> tag serves the same purpose, while providing a cleaner design and a faster performance.
> 
> Let us make comparison with <iframe> in HTML. Everything that is contained by the iframe becomes the part of the render tree. For example, if a specific region within the contained iframe changes its appearance, the render tree "knows" to re-render that particular region.

Agreed, that's the key difference.

> In short, to make a comparison with HTML, external images (non-HTML) are embedded via the <img> tag, while external HTML files are embedded via the <iframe> tag, and the separate logic applies to each of these two separate cases by design. On the other hand, in SVG, external SVG images are embedded in the same manner as non-SVG images via the <image> tag, and this can only work if the SVG's container has specific logic to handle the two cases separately. Since this logic does not currently exist in WebKit, it needs to be implemented, separately, in each of the SVG's container classes.

I'm not sure I follow here.
The 'SVGImage' class, is used to render an external foo.svg images, when using <img src="foo.svg"..> from a HTML or SVG document (HTMLImageElement / SVGImageElement). When rendering pure raster images aka. <img src="test.jpg"> the class is not used.
SVGImage doesn't integrate the 'target' documents rendering/DOM tree and the host document in any way.

I'm having trouble with:
" On the other hand, in SVG, external SVG images are embedded in the same manner as non-SVG images via the <image> tag, and this can only work if the SVG's container has specific logic to handle the two cases separately."

This is exactly what SVGImage is used for, any-non .svg image source is handled through WebCore::Image, and external .svg images are handled through WebCore::SVGImage.

To summarize, I don't see the problem "Since this logic does not currently exist in WebKit" as this kind of distinction exists and is implemented in trunk.

Can you elaborate what I'm misunderstanding or you? :-)

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