android: restore vertical centering for content-hugging custom top-bar buttons

[Yoavpagir]

Summary

Custom React top-bar buttons (topBar.leftButtons / rightButtons with { component }) that have no explicit height render pinned to the top of the bar instead of vertically centered on Android. It affects any content-hugging button — both text (e.g. an Owner-app "Publish" button) and fixed-size images (the profile-picture / avatar left button) — not just text.

This is the vertical-alignment regression that came back with #8328 (RNN 8.8.9). #8328 correctly fixed the New-Architecture width collapse, but as part of it changed the no-explicit-dimension height spec from AT_MOST (what #8326 used) to EXACTLY the full bar height.

Root cause

With EXACTLY full-bar height, the hosted ReactSurfaceView is forced to fill the whole bar. Centering then relies entirely on the content centering itself (a flex container with justifyContent: 'center'). #8328 was validated only against such a self-centering flex button, so it missed the common case: a content-hugging button (<View><Text>…</Text></View>, or a fixed-size avatar image) is laid out at the top of the filled box → top-aligned.

The CENTER_VERTICAL gravity applied in onViewAdded() (added in #8326) is still present but is moot under a filled height — the child fills the parent, so there is nothing left to center.

Fix

Make the no-explicit-dimension height bounded (AT_MOST) again, keeping #8328's content-hugging width (AT_MOST) untouched. The surface then sizes to its content height and is centered by the toolbar's action-view layout + the existing onViewAdded CENTER_VERTICAL gravity — for all content-hugging buttons (text and image), without requiring each component to self-center.

This recombines:

• android: size custom top-bar component buttons to content (Fabric collapse fix) #8328's width AT_MOST → no Fabric width collapse (~1px), and
• android: stabilize custom top bar button layout #8326's height AT_MOST + gravity → correct vertical centering.

Per #8328's own analysis, only a forced EXACTLY width triggers the Fabric collapse; the height mode is independent, so this does not reintroduce the collapse. Buttons that pass an explicit width/height are unchanged (still measured EXACTLY).

// TitleBarReactButtonView.createHeightSpec(...)
         int availableSize = MeasureSpec.getSize(measureSpec);
-        return makeMeasureSpec(availableSize > 0 ? availableSize : Math.max(resolveActionBarSize(), 1), EXACTLY);
+        return makeMeasureSpec(availableSize > 0 ? availableSize : Math.max(resolveActionBarSize(), 1), AT_MOST);

Changes

• TitleBarReactButtonView.createHeightSpec(...): no-dimension branch EXACTLY → AT_MOST (+ updated the onMeasure comment that documented the filled-height rationale).
• TitleBarReactButtonViewTest: reverted the height assertions android: size custom top-bar component buttons to content (Fabric collapse fix) #8328 flipped — child height-spec mode back to AT_MOST and measured height back to content height (CHILD_HEIGHT) in the missing-dimension / zero-parent / RTL cases. Explicit-dimension button unchanged. contentCenteringReplacesExistingVerticalGravityOnly is now meaningful again (the child is shorter than the bar, so gravity actually centers it).

Validation

• Unit: TitleBarReactButtonViewTest updated/green.
• On-device (Detox, release): Buttons suite — esp. the buttons_navbar snapshot (should render top/navigation-bar buttons in the right order): the round flex component button must stay vertically centered (no snapshot regen expected, since AT_MOST height ≈ legacy content-sizing); Stack suite green.
• Manual (engine RC): Owner-app "Publish" text button vertically centered & not clipped; profile/avatar left button vertically centered; Spaces RTL notification + bell still present (no collapse).

Context & links

• Follow-up to android: size custom top-bar component buttons to content (Fabric collapse fix) #8328 (RNN 8.8.9), android: stabilize custom top bar button layout #8326, android: fix custom top bar button measurement #8320, RTL fix for top bar icons #8306 — the chain of Android custom top-bar button measurement changes.
• Re-bumps after the engine bump that shipped android: size custom top-bar component buttons to content (Fabric collapse fix) #8328: https://github.com/wix-private/mobile-apps-engine/pull/3470
• RNN history:
  • android: size custom top-bar component buttons to content (Fabric collapse fix) #8328 — android: size custom top-bar component buttons to content (Fabric collapse fix) #8328 (Fabric collapse fix that introduced this alignment regression)
  • android: stabilize custom top bar button layout #8326 — android: stabilize custom top bar button layout #8326
  • android: fix custom top bar button measurement #8320 — android: fix custom top bar button measurement #8320
  • RTL fix for top bar icons #8306 — RTL fix for top bar icons #8306
• Jira:
  • WOAINFRA-3363 — https://wix.atlassian.net/browse/WOAINFRA-3363 ("Publish" button missing/misaligned, Owner app)
  • WOAINFRA-3362 — https://wix.atlassian.net/browse/WOAINFRA-3362 (related: Android RTL header icons, Fit/Spaces)