Window's material property using MacosApp

[oleksiiparf]

Is it possible to make the window's subview material translucent (await WindowManipulator.setMaterial(NSVisualEffectViewMaterial.fullScreenUI)) while using MacosApp?

Currently, the window appears translucent briefly at startup, before MacosApp/MacosWindow is built. After that background is changed and translucent effect not visible anymore. Except sidebar, because it's wrapped with TransparentMacOSSidebar widget(it has hardcoded NSVisualEffectViewMaterial.sidebar setting).

Wrapping MacosScaffold or it's body with TransparentMacOSSidebar is not a solution because it's not stable and translucent effect is applied partially or not always.

[Adrian-Samoticha]

Currently, NSVisualEffectViewMaterial.windowBackground is hard-coded into macos_ui’s WallpaperTintedArea widget, which is used by the MacosScaffold widget, which indeed makes it impossible to apply different materials. However, adding configuration options that would allow the user to use different materials wouldn’t help much, as using a translucent background would break all widgets that rely on Flutter’s BackdropFilter class due to a Flutter issue that we cannot fix, see flutter/flutter#16296. Due to this issue, translucent widgets that apply a blur filter to their backgrounds would look somewhat like this:

The reason for this is that the alpha channel doesn’t get blurred by Flutter’s BackdropFilter and implementing custom backdrop filters is currently impossible until the aforementioned Flutter issue is resolved (it’s been six years since the issue was opened, so don’t hold your breath).

This is the reason why we are currently disabling wallpaper tinting whenever a transparent widget is shown on-screen. It simply isn’t possible to show an NSVisualEffectViewMaterial without breaking the backdrop filter in the process.

[oleksiiparf]

Thanks for the detailed explanation!

So it appears that if I want to achive translucent background effect for Scaffold widget like it is implemented in macos_window_utils example - I should switch to CurertinoApp and CupertinoPageScaffold widgets, right?

[Adrian-Samoticha]

That should work, though I believe the CupertinoPageScaffold also makes use of backdrop filters (to blur UI elements as you’re scrolling), so beware of that.