fix(ios): preserve Liquid Glass on iOS 26 by skipping custom UITabBarAppearance

[deepak0x]

Problem

On iOS 26, the system provides a Liquid Glass material for UITabBar automatically. However, updateTabBarAppearance() in TabViewImpl.swift calls configureStandardAppearance(), which creates a custom UITabBarAppearance with explicit background and item styling. Apple's WWDC25 session 284 ("Build a UIKit app with the new design") says:

"Remove any background customization from your navigation and toolbars. Using UIBarAppearance or backgroundColor interferes with the glass appearance."

So any app using react-native-bottom-tabs on iOS 26 gets an opaque tab bar instead of Liquid Glass, even with UIDesignRequiresCompatibility = false in Info.plist.

Fix

Add an early return in updateTabBarAppearance() on iOS 26+ when:

• No explicit barTintColor is set (the app wants the system default)
• scrollEdgeAppearance is not "opaque" (the app is not requesting an opaque bar)

In this case, we skip configureStandardAppearance() and let iOS render Liquid Glass. The inactive tint color is still applied via tabBar.unselectedItemTintColor for apps that set tabBarInactiveTintColor.

If the app sets a custom barTintColor or requests an opaque appearance, the existing code path runs as before. On iOS 25 and below, the early return is guarded by #available(iOS 26.0, *) so the existing code path is completely unchanged.

Testing

Tested with the Rocket.Chat React Native app connected to a live server. Liquid Glass renders on the tab bar after the fix. Without it, the tab bar is opaque.

Related to #439

[deepak0x]

hey @maintainers pls check this pr
Thanks ;)

[thiagobrez]

Hey @deepak0x , thanks for the PR! Would you mind sharing some screenshots and relevant snippets / prop configuration to achieve them 🙏🏻

Thank you

[deepak0x]

Hey @thiagobrez, thanks for the quick look! Here are the prop configurations corresponding to the three branches the fix touches. Screenshots attached below.

1. Liquid Glass (new behavior on iOS 26)

No barTintColor, no opaque request — iOS renders its native Liquid Glass material.

<TabView
  navigationState={{ index, routes }}
  onIndexChange={setIndex}
  renderScene={renderScene}
  // no barTintColor
  // no scrollEdgeAppearance="opaque"
  tabBarInactiveTintColor="#8E8E93" // still applied via unselectedItemTintColor
/>

2. Custom opaque bar (existing path, unchanged)

Setting barTintColor keeps the original configureStandardAppearance() code path so the custom color is honored.

<TabView
  navigationState={{ index, routes }}
  onIndexChange={setIndex}
  renderScene={renderScene}
  barTintColor="#FFFFFF"
/>

3. Explicit opaque request (existing path, unchanged)

Setting scrollEdgeAppearance="opaque" also runs the original path, so apps that intentionally want an opaque bar on iOS 26 still get one.

<TabView
  navigationState={{ index, routes }}
  onIndexChange={setIndex}
  renderScene={renderScene}
  scrollEdgeAppearance="opaque"
/>

On iOS 25 and below, all three configurations behave exactly as before — the early return is guarded by #available(iOS 26.0, *).

Screenshots below

before this fix it was a opaque tab bar i.e. configuration two...!

[thiagobrez]

@deepak0x Appreciate it! I'll try to find the time to look into this again this week.

FYI: I think you forgot to attach the screenshots 😆