Bug 28234 – AXTextMarkers: AccessibilityRenderObject::boundsForVisiblePositionRange is wrong in some cases

• Component: Accessibility
• Status: RESOLVED WONTFIX

[chris fleizach]

When there is a block of text followed by a link, the bounds for certain ranges is wrong (specifcally the ranges retreived when asking for next line ranges)

[chris fleizach]

Created attachment 34698 [details]
patch

I'm no expert about Position(s) but here is what I found comparing two cases.

case 1) a block of text 
case 2) a block of text with a link following the text.

Goal: To retrieve the bounds of the second line of text in the block.

In the first case, [Position.cpp:983]

box = searchAheadForBetterMatch(textRenderer);

finds nothing because there's nothing else in the list of siblings. It uses its initial m_offset as the caretPosition.. bounds are then calculated correctly.

In the second case, same line position

box = searchAheadForBetterMatch(textRenderer);

finds the InlineRenderer for the anchor tag. it uses that box's caretMinOffset, which is zero, instead of m_offset. Now the bounds are messed up because 
we think the caret offset is back to zero

My fix, which may be incorrect (but doesn't seem to cause any regression test failures), is that we should only reset the caretOffset to the new box's offset
if it's > than the current offset (because we're looking downstream in this case, we shouldn't get a offset less than what we started).

[Darin Adler]

Comment on attachment 34698 [details]
patch

To me this looks like a workaround for a bug in searchAheadForBetterMatch. Is it possible to fix searchAheadForBetterMatch instead? Are there other calls that would benefit from a fix to that function?

[chris fleizach]

i'll have to look at that method. i'm not sure how many other clients use the bounding boxes of text markers

[chris fleizach]

Comment on attachment 34698 [details]
patch

will look at searchAheadForBetterMatch

[chris fleizach]

after studying this more, i can't say for sure this is a webkit bug. it may just be a misunderstanding in how the clients are using this API