[webkit-dev] Table hit testing

Fady Samuel fsamuel at google.com
Thu May 20 13:52:25 PDT 2010

I'm still confused about the proper ordering of painting/hit testing cells
for a given grid position.

In the example you provided, David, WHY does cell 7 have precedence over
cell 5? Is it based on the order they're defined?



On Thu, May 20, 2010 at 4:47 PM, Peter Kasting <pkasting at google.com> wrote:

> On Thu, May 20, 2010 at 1:38 PM, David Hyatt <hyatt at apple.com> wrote:
>> This is all coming back to me now.
>> When two cells occupy the same position in the grid, only one of them gets
>> stored at that position.  The current code puts the first cell encountered
>> into the grid. This means if you ask what cell is present in row 3 and
>> column 2 of the above example, you'll get back cell #5.
>> This actually makes the grid unsuitable for hit testing and is why I
>> hadn't converted nodeAtPoint over to use the grid yet.
>> The grid needs to be fixed so that it records all of the cells present at
>> a given position.  If it did that, then you could binary search as long as
>> there are no overflowing cells, since you'd then be able to see all the
>> cells that actually occupy a given grid position.
>> The paint method uses the grid and actually has a repaint bug, since if
>> you make the repaint rect tight enough, it won't think it has to paint the
>> second and subsequent cells that occupy a given grid position.
> It sounds like your recommended steps are:
> * First fix the grid to record all the cells at a given position.  This
> fixes a repaint bug.
> * Then change the hit-testing to work just like painting.  This makes hit
> testing more efficient and ensures hit testing and painting agree.
> * Then optimize hit-testing to binary-search if there are no overflowing
> cells.  (And optimize painting similarly?  I dunno what that would mean,
> though--just going off the "optimize together" comment earlier.)
> Is this a good summary?
> PK
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