Bug 52045 – SVG image in HTML changes size as the window is resized

• Component: SVG
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

Created attachment 78209 [details]
SVG image for testcase

I'm seeing a very weird effect with butterfly.svg in an <img> element. Testcase coming.

[Simon Fraser (smfr)]

Created attachment 78210 [details]
Testcase

For some reason, the butterfly image in the <img> changes size based on the window size.

[Nikolas Zimmermann]

Ouch, stupid bug. One of the many cases, where we're not taking care of the SVG embedded in HTML correctly. 
If you set isLayoutSizeChanged to false, hardcoded in SVGRenderSupport.cpp:

void SVGRenderSupport::layoutChildren(RenderObject* start, bool selfNeedsLayout)
{
    bool layoutSizeChanged = false; //findTreeRootObject(start)->isLayoutSizeChanged();

Does the problem disappear?

[Simon Fraser (smfr)]

> void SVGRenderSupport::layoutChildren(RenderObject* start, bool selfNeedsLayout)
> {
>     bool layoutSizeChanged = false; //findTreeRootObject(start)->isLayoutSizeChanged();
> 
> Does the problem disappear?

No.

[Simon Fraser (smfr)]

This seems to be related to this code in RenderImage::computeReplacedLogicalWidth():

    if (m_imageResource->imageHasRelativeWidth())
        if (RenderObject* cb = isPositioned() ? container() : containingBlock()) {
            if (cb->isBox())
                m_imageResource->setImageContainerSize(IntSize(toRenderBox(cb)->availableWidth(), toRenderBox(cb)->availableHeight()));
        }

which was added in http://trac.webkit.org/changeset/28856

I don't grok why the image container size would be relative to the size of the containing block. Beth, do you recall?

[Beth Dakin]

(In reply to comment #4)
> This seems to be related to this code in RenderImage::computeReplacedLogicalWidth():
> 
>     if (m_imageResource->imageHasRelativeWidth())
>         if (RenderObject* cb = isPositioned() ? container() : containingBlock()) {
>             if (cb->isBox())
>                 m_imageResource->setImageContainerSize(IntSize(toRenderBox(cb)->availableWidth(), toRenderBox(cb)->availableHeight()));
>         }
> 
> which was added in http://trac.webkit.org/changeset/28856
> 
> I don't grok why the image container size would be relative to the size of the containing block. Beth, do you recall?

I don't recall all of the specifics…but I think that we decided to treat SVG-as-image as a regular image with width:100%, which would calculate based on the containing block.

[Simon Fraser (smfr)]

(In reply to comment #5)
> (In reply to comment #4)
> > This seems to be related to this code in RenderImage::computeReplacedLogicalWidth():
> > 
> >     if (m_imageResource->imageHasRelativeWidth())
> >         if (RenderObject* cb = isPositioned() ? container() : containingBlock()) {
> >             if (cb->isBox())
> >                 m_imageResource->setImageContainerSize(IntSize(toRenderBox(cb)->availableWidth(), toRenderBox(cb)->availableHeight()));
> >         }
> > 
> > which was added in http://trac.webkit.org/changeset/28856
> > 
> > I don't grok why the image container size would be relative to the size of the containing block. Beth, do you recall?
> 
> I don't recall all of the specifics…but I think that we decided to treat SVG-as-image as a regular image with width:100%, which would calculate based on the containing block.

But in this testcase the image has a fixed size. I don't see why the containing block would come into it.

[Beth Dakin]

(In reply to comment #6)
n this testcase the image has a fixed size. I don't see why the containing block would come into it.

Yeah, I definitely agree that there is a bug in the code.

[Tim Horton]

<rdar://problem/5812360>

[Nikolas Zimmermann]

47156 fixes this.

[Nikolas Zimmermann]

Fixed in r98852. Thanks for the testcase!