On Wed, 8 Apr 2026 17:58:25 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. > > Martin Fox has updated the pull request with a new target base due to a merge > or a rebase. The pull request now contains eight commits: > > - Merge remote-tracking branch 'upstream/master' into osbackdrop > - Backdrops are now objects created by specifying a material. The > list of materials is now open-ended. > - Merge remote-tracking branch 'upstream/master' into osbackdrop > - Merge remote-tracking branch 'upstream/master' into osbackdrop > - Merge remote-tracking branch 'upstream/master' into osbackdrop > - Removed unused import > - Merge remote-tracking branch 'upstream/master' into osbackdrop > - OS supplied translucent window backdrops For Linux/Wayland support, the ext-background-effect-v1 protocol (which is now implemented in KWin, with KDE Plasma 6.7 shipping this support on June 16, 2026, [wlroots](https://gitlab.freedesktop.org/wlroots/wlroots/-/blob/master/include/wlr/types/wlr_ext_background_effect_v1.h) and [Niri](https://github.com/niri-wm/niri/pull/3483) with planned support coming to other DE's such as [Cosmic](https://github.com/pop-os/cosmic-comp/pull/2179) and [Hyprland](https://github.com/hyprwm/Hyprland/pull/13211) as well as others) could be a viable path forward. Unlike some of the platform-specific constraints discussed above, this protocol supports dynamically adding/removing background effects, which aligns with the goal of supporting setBackdrop() after the window is shown. Reference: https://wayland.app/protocols/ext-background-effect-v1 Real-world implementations in Ghostty (https://github.com/ghostty-org/ghostty/pull/10727) and Quickshell (https://github.com/quickshell-mirror/quickshell/pull/566) demonstrate how this works in practice. This would only cover Wayland, of course X11 would likely need a separate mechanism or remain unsupported for backdrops. Most major desktop environments now default to Wayland, so this would cover the majority of Linux users. Additional notes: KDE 6.7, which includes [ext-background-effect-v1](https://www.phoronix.com/news/KDE-Brings-Back-Air-Theme), is planned for release on [Tuesday 16th June 2026](https://9to5linux.com/kdes-new-css-based-style-engine-union-is-coming-to-kde-plasma-6-7). For testing purposes you can test this on KDE Neon Unstable edition as a Live ISO or in a VM: https://neon.kde.org/download ------------- PR Comment: https://git.openjdk.org/jfx/pull/2048#issuecomment-4389774140
