RFR: 8375578: Enable translucent window backdrops

[Christopher Schnick]

On Thu, 29 Jan 2026 16:27:53 GMT, Martin Fox <mfox at openjdk.org> wrote:

>> Depending on how long this takes, would it be possible to extract the fix for the unified stage BackBufferFormat (if it actually fixes all cases) as a separate PR? That would make the review easier to split a feature addition and bugfix into two issues. I can definitely do the testing for the fix
>
>> Depending on how long this takes, would it be possible to extract the fix for the unified stage BackBufferFormat (if it actually fixes all cases) as a separate PR?
> 
> It would probably be faster for you to test and submit the PR yourself. The fix is just the two lines in native-prism-d3d where the BackBufferFormat is set to D3DFMT_A8R8G8B8 instead of being left unspecified. Based on the write up for bug [JDK-8154847](https://bugs.openjdk.org/browse/JDK-8154847) if you don't set the back buffer format what you get varies depending on the graphic card. It should be OK to enable alpha unconditionally, in the end it should only affect UNIFIED. Most stage styles wipe out the alpha channel by drawing an opaque background. The exceptions are TRANSPARENT and UNIFIED and only UNIFIED uses the swap chain.
> 
> If you'd prefer I can enter the PR but it would probably have to wait until next week.

@beldenfox you can now rebase on master and remove the BackBufferFormat adjustments in this PR. That should make this PR more straightforward

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PR Comment: https://git.openjdk.org/jfx/pull/2048#issuecomment-3855015482