On May 18, 2010, at 12:52 PM, Fady Samuel wrote:
> Hi all,
> 
> I'm looking at table hit testing, and in all the simple test cases I've 
> tried, it seems to show that RenderTable never has the flag m_hasOverflowClip 
> set to true. What this means is that all the table's children are ALWAYS 
> checked on all mouse events. For large tables, or pages with many tables, 
> this sounds awfully taxing on the processor for no good reason.
> 
> See RenderTable::nodeAtPoint in 
> third_party/WebKit/WebCore/rendering/RenderTable.cpp . It seems 
> "hasOverflowClip()" is always false.
> 
> Can we not compute a bounding box for the table on layout? Are there any 
> complications here that I should be aware of that resulted in this 
> inefficient solution? 

m_hasOverflowClip is about overflow:auto/scroll/hidden.  The default value for 
overflow is visible, so that's not going to be set and isn't really relevant to 
your problem.

Both RenderTable and RenderTableSection need to have their nodeAtPoint methods 
patched to be like their paint methods instead.  Both of those methods would 
get much more efficient if we did that.

dave
(hy...@apple.com)

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