[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 23:26:28 UTC 2012

Hi, Jim.
21.12.2012 1:42, Jim Graham wrote:
> Hi Sergey,
> Avoiding the transform only works if they read it back in the same 
> coordinate system that they set it.  It will fail if they do:
>     setClip or clip(...);
>     scale(5, 5);
>     getClip();
> So, given that we have to deal with the transform/untransform issues 
> anyway then a user-space clip caching solution isn't going to solve 
> the immediate problem for all cases.
Yes, right, second solution does not work in this case.
> I'd have to look closely at the code to know for sure, but I imagine 
> that it would be easy enough to ensure that the [un]transform methods 
> always turn a rectangle with 0 dimensions into another rectangle with 
> 0 dimensions (whether one or both are 0). 
Well, I expect that solution from the webrev does this, isn't it? 
Approach is simple if we have correct clip from the user, we always get 
correct clip after transformation, and vice versa.
> The setFFD normalization only hurts us when we have negative 
> dimensions, but it should be OK with 0 dimensions, no?  So, if we 
> normalize negative dimensions to 0 going in then it might be safe?
Do you mean just change Rectangle(0,0,-100,-100) to (100,100,0,0)? How 
we can revert back this operation?

>             ...jim
> On 12/20/2012 9:52 AM, Sergey Bylokhov wrote:
>> 20.12.2012 14:12, Sergey Bylokhov пишет:
>>> 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.
>> Another solution: don't use transformShape/untransformShape in the
>> set/get methods. store usrClip as is, and transform usrClip->usrClipTmp
>> in validateCompClip().
>> In this case setters/getters will become much simpler.
>>>>             ...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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