On Wed, 21 Jan 2026 20:15:16 GMT, Martin Fox <[email protected]> wrote:
> This PR enables translucent window backdrops for JavaFX stages on macOS and > Windows 11. Since we’re reliant on the operating system for these effects > (they typically require real-time blurring of the desktop) I needed to flesh > out a fairly complete prototype to sort out the API. I will start a > discussion about the API on the mailing list. > > There’s a crude manual test for trying out the different backdrop materials. > > java @build/run.args -Djavafx.enablePreview=true > tests/manual/stage/BackdropTest.java > > You’ll want to drag the windows around to avoid having them overlap each > other since they’re all created in the center of the screen. For windows > without title bars you can click anywhere on the background to drag the > window except for TRANSPARENT stages on Windows which are a bit tricker to > get a hold of; try to click on a text label. > > If you create an UNDECORATED stage on Windows the backdrop won’t be > translucent initially. This can be corrected by changing the stage’s color > scheme. This is an OS bug that I haven’t found a workaround for. > > The changes on Windows 11 are minimal since we’re just invoking an OS feature > by calling DwmSetWindowAttribute. I did need to make two small changes to the > D3D9 Prism code to ensure that the swap chain and back buffer support an > alpha channel so JavaFX can composite its content on top of the backdrop. > This is the same way the old UNIFIED stage style worked before it became > unreliable (see [JDK-8154847](https://bugs.openjdk.org/browse/JDK-8154847)). > > On macOS I moved the GlassHostView so it’s now a permanent part of the > NSWindow. For some time the host view has been a remnant left over from an > older approach to implementing fullscreen. Now it serves as a common parent > for the NSVisualEffectView that provides the backdrop and the GlassView3D > that contains the JavaFX content. Making it the permanent contentView of the > NSWindow simplifies some code. > > To validate the API I did prototype this for Windows 10 (thanks @mstr2!). > Well, I prototyped this using DirectComposition so it should work on Win10 > but I can't test Win10 myself. Using DirectComposition is much more involved > so I shelved that implementation for now but it does inform the API. It’s the > reason the backdrop needs to be specified before the Java window is shown and > the platform window created. modules/javafx.graphics/src/main/java/javafx/stage/Stage.java line 574: > 572: /** > 573: * Specifies the backdrop for this stage. This must be done prior to > 574: * making the stage visible. Is there is a reason on why this can't be changed later on? At least in my use cases, changing the backdrop type dynamically later on works without issues ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/2048#discussion_r2715220921
