Bug 34923 – Incorrect client rects for blocks the span multiple columns and their descendants

• Component: Layout and Rendering
• Status: RESOLVED FIXED

Created attachment 48712 [details]
Test case

The DOM getClientRects() API and the -[DOMRange textRects] method return incorrect results for blocks and their descendants when those span more than one column. The attached test case gives an example with getClientRects().

<rdar://problem/7647300>

Created attachment 48716 [details]
WIP

Created attachment 48732 [details]
Allow offsetFromContainer() to return the right offset for a given point in the multi-column case, and pass it the point of interest

This is obviously just a better approximation of correct behavior in the multi-column case, as it still assumes that a quad is mapped to absolute coordinates via a continuous transform. In the multi-column case, the transform is only piecewise-continuous. So this just picks the piece that applies to some point in the quad, rather than always picking the first piece.

[Simon Fraser (smfr)]

Comment on attachment 48732 [details]
Allow offsetFromContainer() to return the right offset for a given point in the multi-column case, and pass it the point of interest

> Index: WebCore/ChangeLog
> ===================================================================
> --- WebCore/ChangeLog	(revision 54757)
> +++ WebCore/ChangeLog	(working copy)
> @@ -1,3 +1,63 @@
> [phone]  Dan Bernstein  <[e-mail]>
> +
> +        Reviewed by NOBODY (OOPS!).
> +
> +        <rdar://problem/7647300> Incorrect client rects for blocks the span multiple columns and their descendants
> +        https://bugs.webkit.org/show_bug.cgi?id=34923
> +

I'd like to see a summary of the problem, and your general approach at fixing it here.

> +        (WebCore::SelectionController::layout): Pass the caretâs origin as the

Garbled curly quote.

> +        column offset to the computation, which previously this function didnât

Ditto

> +        TransformState with the top left corner of the quadâs bounding box. It

And again

> Index: WebCore/rendering/RenderObject.h
> ===================================================================
> --- WebCore/rendering/RenderObject.h	(revision 54757)
> +++ WebCore/rendering/RenderObject.h	(working copy)
> @@ -563,7 +563,7 @@ public:
>      FloatQuad localToContainerQuad(const FloatQuad&, RenderBoxModelObject* repaintContainer, bool fixed = false) const;
>  
>      // Return the offset from the container() renderer (excluding transforms)
> -    virtual IntSize offsetFromContainer(RenderObject*) const;
> +    virtual IntSize offsetFromContainer(RenderObject*, const IntPoint&) const;

I'd like the comment to explain what the point is for.

> +    virtual void adjustForColumns(IntSize&, const IntPoint&) const { }

Also here. How is the IntSize being adjusted? What does the point represent?

r=me, with some addition commentary.

Fixed in <http://trac.webkit.org/projects/webkit/changeset/54784>.