RFR: 8357299: Graphics copyArea doesn't copy any pixels when there is overflow

[Sergey Bylokhov]

On Wed, 21 May 2025 03:17:34 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> Graphics copyArea overflow check bails out of copying pixels if there is overflow.
> The spec says ""If a portion of the source rectangle lies outside the bounds of the component, or is obscured by another window or component, {@code copyArea} *will be unable to copy* the associated pixels"
> 
> which suggests that we should always copy the parts inside the bounds and never the parts outside the bounds
> but it seems currently, in the case of overflow it no longer copies any pixels, including the parts that are inside. 
> So, the fix clips the copyarea region to clip bounds so it will only affect pixels within the valid bounds, and any pixels outside will be ignored.

src/java.desktop/share/native/libawt/java2d/loops/Blit.c line 88:

> 86:                         ? clipInfo.bounds.y2 : (dsty + height);
> 87:     if (UNSAFE_TO_SUB(srcx, dstx) ||
> 88:         UNSAFE_TO_SUB(srcy, dsty)) {

we also should check this part of the code, is it correct to simply exit here, or should we instead calculate and use the maximum distance we can handle?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25340#discussion_r2114891163