On Fri, 27 Aug 2021 17:34:25 GMT, Jose Pereda <jper...@openjdk.org> wrote:
>> I'm more worried about correctness than performance. Setting a clip does not >> necessarily imply that the clipped region should be cleared. So this feels a >> bit like a workaround for a missing `clearRect` elsewhere. I wonder if there >> is code somewhere that assumes that if the fill color is fully transparent >> it can skip the call to `clearRect`? > > I guess the assumption might be the other way around? Since the fill color > was not transparent, there was no need to clear the area, when rendering the > same solid rect at the new position? > > If you check this > [comment](https://bugs.openjdk.java.net/browse/JDK-8090547?focusedCommentId=13808421&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13808421), > there is already a mention that `WCPageBackBufferImpl::copyArea` doesn't > care about the alpha channel. > > The proposed patch: > > texture.createGraphics().clearQuad(x+dx, y+dy, x+dx+w, y+dy+h); > > could work if we could apply it conditionally only for alpha == 0 (or maybe > also for alpha < 1). > > My current approach with `clearRect` ultimately calls `clearQuad`, so both > might be doing the same after all. I don't doubt that the area should be cleared. What I was questioning is whether this was the best place to do it? I'd be OK with it if you document it. ------------- PR: https://git.openjdk.java.net/jfx/pull/563
