[OpenJDK 2D-Dev] [8] Request for review: 8004859 Graphics.getClipBounds/getClip return difference nonequivalent bounds, depending from transform.

Sergey Bylokhov Sergey.Bylokhov at oracle.com
Thu Dec 20 10:12:20 UTC 2012

20.12.2012 13:49, Jim Graham wrote:
> More to the point, if you substitute a 0x0 clip when an incoming clip 
> is an empty rectangle then it will always be empty under any kind of 
> transform.  This could be done by performing a "max(w,0);max(h,0);" 
> operation on the incoming data.  Once a clip is accepted as non-empty, 
> then I think the current code will adequately deal with flipped 
> transforms, won't it?
Yes, but with one exception. What to do with getClip:untransformShape 
methods in this case, it executes the reverse transformation.
The question is: if the incoming clip is an empty how to store it? If we 
did not transform incoming clip, we should change 
getClip/clip/untransformShape + some flag which should indicate that 
incoming clip(not a result of transformation) was empty.
>             ...jim
> On 12/19/2012 8:47 PM, Jim Graham wrote:
>> Hi Sergey,
>> This is all a lot more complicated than I think it needs to be. Why not
>> just detect incoming empty rectangles and force an empty composite clip
>> in that case?  No heuristics necessary...
>>              ...jim
>> On 12/15/2012 9:26 AM, Sergey Bylokhov wrote:
>>> Hi, Jim.
>>> Could you please review the updated version of the fix:
>>> http://cr.openjdk.java.net/~serb/8004859/webrev.01
>>> 14.12.2012 0:40, Jim Graham wrote:
>>>> This fix breaks other behavior.
>>>> You need to use setFrameFromDiagonal on the results of the transform
>>>> because a flip or rotation can cause the transformed points to be
>>>> unordered and setFFD will sort them as they need to be.  It is the
>>>> incoming rectangle that needs to be checked for being empty, not the
>>>> results of the transform.
>>> In the new version I restore coordinates relation, if it were changed
>>> during transform.
>>> Swap needed:
>>>   - If the user provide incorrect rectangle and after transformation we
>>> get correct rectangle.
>>>   - If the user provide correct rectangle and after transformation we
>>> get incorrect rectangle.
>>>> The case that will fail with this fix is setting the clip to a valid
>>>> rectangle in a coordinate system that is rotated by a multiple of 90
>>>> degrees or is flipped horizontally or vertically. Those cases will
>>>> result in an empty clip, but the clip was not empty coming in...
>>>>             ...jim
>>>> On 12/13/2012 3:08 AM, Sergey Bylokhov wrote:
>>>>> Hello,
>>>>> Please review the fix for jdk 8.
>>>>> Change description:
>>>>> 1 transformShape now symmetric to untransformShape()
>>>>> (setFrameFromDiagonal was removed).
>>>>> 2 getClipBounds now always uses getBounds2D which does not return 
>>>>> empty
>>>>> Rectangle if the userclip has negative width or height.
>>>>> Note that if the userclip has negative width or height, our real
>>>>> graphic
>>>>> clip will be empty/no-area. This wasn't true before the fix for the
>>>>> scaled graphics.
>>>>> Bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8004859
>>>>> Webrev can be found at:
>>>>> http://cr.openjdk.java.net/~serb/8004859/webrev.00

Best regards, Sergey.

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