On Thu, 22 Jan 2026 04:04:48 GMT, Christopher Schnick <[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 I prototyped a version of this for Win10. On that platform we have to roll our own backdrops using DirectComposition or Windows.UI.Composition and that requires building the HWND a little differently, firing up a different painter, and re-plumbing the way pixels are delivered from Prism. I'm not entirely sure we can set all that up after the HWND is created. It's just far far easier to have the backdrop in hand from the start. (Well, all we really need to know when we create the platform window is that we'll be using a backdrop. The actual backdrop choice could be specified dynamically later but I wasn't sure what purpose that would serve.) I'm not sure how this would work on Linux. The Wayland folks recently added an extension for blurring window backgrounds and it looks like it can be dynamically added and removed but I can't test that right now and have no idea which compositors have implemented it. ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/2048#discussion_r2718445867
