[graphics]  Review request for 8155903: Crash while running imported/w3c/canvas/2d.gradient.interpolate.overlap2.html
james.graham at oracle.com
Mon May 9 18:21:25 UTC 2016
That looks good for the case where Imin is zero, but it appears that we could also have overflow as well, with a single
very tiny Imin the accumulation of estimatedSize with an "int" type could easily overflow and become essentially a
random number. Changing the estimatedSize variable to a float should prevent that related issue...
On 5/9/16 6:16 AM, Arunprasad Rajkumar wrote:
> Hello Jim,
> Thanks for your suggestions. As of now I taking an easy way to fix the issue, New changes are available at
> I couldn't write a reliable test case using public javafx APIs, the behavior is intermittent. However I could
> consistently produce the issue using our DRT internal test case which is based on W3C functional test.
>  http://w3c-test.org/2dcontext/fill-and-stroke-styles/2d.gradient.interpolate.overlap2.html
> On 5/5/2016 11:51 PM, Jim Graham wrote:
>> Hi Arun,
>> The change you made to the calculateSingleArray method looks like it produces a bad array of color stops for the case
>> where Imin is 0. You should fall into the calculateMultipleArray method instead which should not have any trouble
>> with zero length intervals. At that point you don't have to have any code in calculateSingleArray that deals with
>> Imin being zero because that can be part of its calling contract.
>> That is the quick fix.
>> The harder fix that would let us maintain speed when there is a zero interval would be to teach the code what to do in
>> that special case. Basically a zero interval means that we have a case where approaching the interval point from the
>> left is interpolating towards colorA, but leaving that point from the right is interpolating from colorB, with a
>> sudden transition between those 2. In that case, a zero interval shouldn't affect the Imin, since the Imin is trying
>> to determine the size of each interpolated region and we don't interpolate across a zero-sized interval. So, the scan
>> for Imin would simply ignore zero length intervals. Later, the code that populates the array in the
>> calculateSingleArray function would know that the zero length interval simply means swap in a new "from color" without
>> any actual interpolation.
>> Getting that harder fix right would require a lot of testing, so it may be better to do the quick fix now to stop the
>> exceptions and then deal with the optimization as a tweak filed for later...
>> On 05/05/2016 01:57 AM, Arunprasad Rajkumar wrote:
>>> Hello Jim,
>>> Please review the below patch.
>>> JIRA: https://bugs.openjdk.java.net/browse/JDK-8155903
>>> Webrev: http://cr.openjdk.java.net/~arajkumar/8155903/webrev.01
>>> Issue: Divide by zero while adding multiple gradient stops at same offset.
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