android: size custom top-bar component buttons to content (Fabric collapse fix)#8328
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israelko wants to merge 7 commits into
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android: size custom top-bar component buttons to content (Fabric collapse fix)#8328israelko wants to merge 7 commits into
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…ports its size On the New Architecture (Fabric), a custom React-component top bar button without explicit width/height could collapse to ~1px. The hosted React surface lays out asynchronously, off the native measure pass, so the first onMeasure often observes a 0-sized child and freezes the button at the ~1px floor with no subsequent re-measure. Attach an OnLayoutChangeListener to the hosted child that re-requests layout when the content's size changes (so onMeasure re-runs and sizes the button to the content). The size-changed guard makes it converge once the button matches the content. The explicit-dimensions check is done inside the listener because onViewAdded fires from the superclass constructor (before `component` is assigned) for the React surface view we need to observe. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The new test hardcoded the collapsed button width as 1px, which only holds at mdpi (density 1.0). CI runs at a higher density, where resolveFinalWidth(0) = ceil(dpToPx(1dp)) > 1. Derive the expected value from the same dpToPx formula the production code uses instead of hardcoding it. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The re-measure assertion failed (expected 25 but was 1) because View.measure() caches results: re-measuring the button with the same outer spec reused the child's stale cached 0-width measurement, so resolveFinalWidth still saw 0. In production RN re-measures the surface when it lays out new content; model that with child.forceLayout() (after child.layout(), which clears FORCE_LAYOUT) so the parent's super.onMeasure observes the real content width. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…e bounded measure Custom React-component top bar buttons without explicit width/height collapsed to ~1px (invisible) under the New Architecture (Fabric). The two-pass measurement from #8320/#8326 re-measured the hosted ReactSurfaceView with an EXACTLY box derived from the first (often still-empty) discovery pass; that forced box is pushed to Fabric via updateLayoutSpecs, so Fabric keeps laying the content out into the collapsed box and the button never recovers. The same forcing also stretched flex-content buttons to the full bar height. Replace the two-pass with a single bounded (AT_MOST) measure and let ReactSurfaceView size itself to its content (its documented AT_MOST max-of-children behavior). When Fabric mounts/sizes the content it re-requests layout and this measure runs again against the real content size. Explicit width/height still measure EXACTLY; vertical centering is preserved by the existing CENTER_VERTICAL gravity. Verified on-device (Pixel 7, newArch+Hermes) on RN 0.78.3 and 0.85.2: content-hugging and flex component buttons render correctly; flex buttons are pixel-identical to before. Unit tests updated for the single-pass contract. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
israelko
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Ligamer24
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Jun 11, 2026
… vertically centered The previous commit fixed the collapse by measuring the React surface with a single bounded (AT_MOST) pass, but using AT_MOST for the *height* let content-hugging surfaces shrink, which shifted self-centering content (e.g. a flex container with justifyContent:'center') downward — the playground buttons_navbar snapshot caught this as an off-center round button on Fabric. Measure the height EXACTLY to the available bar height instead. A filled height box lets the React content center itself in the bar (matching the legacy two-pass layout), while the width stays AT_MOST so the surface still sizes to its content and the collapse fix is preserved (forcing the width is what caused the collapse; forcing the height does not). Verified on a Pixel 3a / API emulator (the CI device profile) in release: the buttons_navbar snapshot test passes (centering matches), and the full Buttons (14/14) and Stack (20/20) Detox suites pass. Unit tests updated for the filled-height contract. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
topBar.leftButtons/rightButtonswith{ component }) collapsing to ~1px (invisible) on Android under the New Architecture (Fabric) when they don't declare explicitwidth/height. A content-hugging button (e.g.<View><Text/></View>) disappears entirely; as a left button it also takes the back-button slot, so the back affordance appears to vanish too. Reproduces on RN 0.78.3 and 0.85.2 (it was masked on 0.85 by flex-content buttons, which fill the constraint).ReactSurfaceViewwith anEXACTLYbox derived from the first (often still-empty) discovery pass. That forced box is pushed to Fabric viaupdateLayoutSpecs, so Fabric keeps laying the content out into the collapsed box and the button never recovers.AT_MOSTso the surface sizes to its content (ReactSurfaceViewreports max-of-children underAT_MOST). Never push a forcedEXACTLYwidth: that's what re-collapses the content.EXACTLYthe available bar height, so content that centers itself (a flex container withjustifyContent:'center') stays vertically centered — matching the legacy layout. Forcing the height does not cause the width collapse.width/heightstill measureEXACTLY(unchanged for those buttons).Validation
TitleBarReactButtonViewTestupdated for the single-pass / filled-height contract — passes.Buttonssuite 14/14 — incl. thebuttons_navbarsnapshot test (should render top/navigation-bar buttons in the right order): the round component button renders vertically centered, matching the committed snapshot — no snapshot regen needed.Stacksuite 20/20.Net effect is a simplification of the measurement logic (removes the two-pass) plus the height-fill that preserves centering.