RFR: 8218745: TableView: visual glitch at borders on horizontal scrolling

[Marius Hanl]

On Fri, 24 May 2024 16:59:20 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> Alternative PR to https://github.com/openjdk/jfx/pull/1330 which does not modify the layout of `VirtualFlow`.
>> 
>> This PR fixes the glitching by removing the code in `NGNode.renderRectClip`, which made many calculations leading to floating point errors.
>> Interestingly I found out, that `getClippedBounds(..)` is already returning the correct bounds that just need to be intersected with the clip of the `Graphics` object.
>> 
>> So the following code is effectively doing the same:
>> 
>> Old:
>> 
>> BaseBounds newClip = clipNode.getShape().getBounds();
>> if (!clipNode.getTransform().isIdentity()) {
>>     newClip = clipNode.getTransform().transform(newClip, newClip);
>> }
>> final BaseTransform curXform = g.getTransformNoClone();
>> final Rectangle curClip = g.getClipRectNoClone();
>> newClip = curXform.transform(newClip, newClip); // <- The value of newClip after the transform is what getClippedBounds(..) is returning
>> newClip.intersectWith(PrEffectHelper.getGraphicsClipNoClone(g));
>> Rectangle clipRect = new Rectangle(newClip)
>> 
>> 
>> New:
>> 
>> BaseTransform curXform = g.getTransformNoClone();
>> BaseBounds clipBounds = getClippedBounds(new RectBounds(), curXform);
>> Rectangle clipRect = new Rectangle(clipBounds);
>> clipRect.intersectWith(PrEffectHelper.getGraphicsClipNoClone(g));
>> 
>> 
>> As you can see, there are very similar, but `getClippedBounds` does a much better job in calculating the bounds.
>> I also wrote a tests proving the bug. I took 100% of the setup and values from a debugging session I did when reproducing this bug.
>> 
>> I checked several scenarios and code and could not find any regressions.
>> Still, since this is change affects all nodes with rectangular clips, we should be careful.
>> Performance wise I could not spot any difference, I do not expect any difference.
>> **So I would like to have at least 2 reviewers.**
>> Note that I will do more testing as well soon on all JavaFX applications I have access to.
>> 
>> ---
>> 
>> As written in the other PR, I have some interesting findings on this particular problem.
>> 
>> Copy&Paste from the other PR:
>> --
>> 
>> Ok, so I found out the following:
>> When a Rectangle is used as clip without any effect or opacity modification, the rendering goes another (probably faster) route with rendering the clip. That's why setting the `opacity` to `0.99` fixes the issue - another route will be used for the rendering.
>> This happens at the low level (`NGNode`) side of JavaFX.
>> ...
>> I could track it down to be a typical f...
>
> modules/javafx.graphics/src/test/java/test/com/sun/javafx/sg/prism/NGNodeTest.java line 626:
> 
>> 624:         @Override
>> 625:         public void setClipNode(NGNode clipNode) {
>> 626:             System.out.println(clipNode);
> 
> should this println be removed?

yes, forgot to remove.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1462#discussion_r1615181856