feat(ios): expose UIGlassEffect clear variant via new backgroundGlass prop

[michelemarri]

Closes #663

Adds a new backgroundGlass?: 'regular' | 'clear' prop on <TrueSheet> so apps can opt into iOS 26's UIGlassEffectStyleClear variant. Naming mirrors the existing backgroundColor / backgroundBlur props per your suggestion in the issue thread.

API

<TrueSheet detents={[0.5, 0.9]} backgroundGlass="clear">
  {/* ... */}
</TrueSheet>

• 'regular' (default): existing behavior — system-default Liquid Glass (.regular style, with luminosity veil for content legibility)
• 'clear': new option → UIGlassEffect(style: .clear, isInteractive: true). High transparency, minimal adaptivity, designed for media-rich backdrops where the app provides its own dimming/blur layer

Precedence

Follows the existing pattern — backgroundColor wins over backgroundBlur, which wins over backgroundGlass. The new prop only kicks in when neither of the other two is set, on iOS 26.1+, and UIDesignRequiresCompatibility is not opted-in.

Scope

• src/fabric/TrueSheetViewNativeComponent.ts — Fabric spec
• src/TrueSheet.types.ts — public TS types (new BackgroundGlass type + prop)
• src/TrueSheet.tsx — destructure + forward to native
• src/navigation/types.ts — add to TrueSheetNavigationSheetProps Pick list
• ios/TrueSheetViewController.h — new @property
• ios/TrueSheetView.mm — wire newProps.backgroundGlass → _controller.backgroundGlass
• ios/TrueSheetViewController.mm — use it in setupBackground

~40 lines added, zero deletions. Fully additive: no behavior change for existing users, default 'regular' preserves current Liquid Glass appearance.

Testing

Deployed in production via patch-package in soglia72 (an Italian fantasy-football app for Serie A). The backgroundGlass="clear" variant is used on a sheet presented over a custom animated pitch canvas, where the system's regular glass veil was washing out the background. No regressions on existing sheets that don't set the prop.

Happy to add docs / changelog entry / example snippet if you'd like — let me know how you prefer to structure additions. Thanks for the library and the quick turnaround on the issue!

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[lodev09]

Hey @michelemarri, thanks for the PR! Looks good to me.
Have you tried building on android? I think this will break, we need a stub for this on android, I think.

Also if you don't mind updating the CHANGELOG. Thank you!

[bigcupcoffee]

Hey I'm also interested in the feature, so I can take this PR over if the OP won't @lodev09
Won't we also need something like backgroundGlassAppearance prop to support specifying dark manually? Essentially a way to do overrideUserInterfaceStyle on-demand, as from what I see there's no way to force something like dark theme on dark-only screen when your general app theme is light right now?

On Android we're only missing

@ReactProp(name = "backgroundGlass")
override fun setBackgroundGlass(view: TrueSheetView, tint: String?) {
  // iOS-specific prop - no-op on Android
}

[lodev09]

@bigcupcoffee feel free to open up separate PR, looks like @michelemarri is MIA lol.

Won't we also need something like backgroundGlassAppearance prop to support specifying dark manually?

I'm not sure if this is available on IOS? If it is, we could add separate options prop for this e.g. backgroundGlassOptions.

[bigcupcoffee]

It's not an explicit property, just a basic view.overrideUserInterfaceStyle should suffice although I'm not sure if I have a view to put it on, I'll play around and find out in a bit I guess