fix(textinput): correct placeholder layout constraints (px vs DIP) and no-op NaN fontSize guard - #16317
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…d no-op NaN fontSize guard Forward-port of microsoft#16303 (0.83-stable) to main. CreatePlaceholderLayout fed m_imgWidth/m_imgHeight - which are physical pixels (frame * pointScaleFactor) - into LayoutConstraints, which are expressed in DIPs. The placeholder was laid out in a box pointScaleFactor times too large, so it measured and positioned at a different height than the typed text. Divide by pointScaleFactor. The NaN fontSize guard was also a no-op: it evaluated defaultTextAttributes().fontSize as a discarded expression statement instead of assigning it, so a placeholder with no fontSize never picked up the default.
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This was referenced Jul 26, 2026
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Pull request overview
This PR forward-ports a TextInput placeholder rendering fix to main by correcting unit mismatches (physical pixels vs DIPs) in placeholder layout constraints and fixing a no-op NaN fontSize fallback so placeholders reliably use the default font size.
Changes:
- Convert placeholder
LayoutConstraints.maximumSizefrom physical pixels (m_imgWidth/m_imgHeight) to DIPs by dividing bym_layoutMetrics.pointScaleFactor. - Fix the NaN
fontSizeguard to actually assign the defaultfontSizeinto the placeholder’sTextAttributes. - Add a change file for the
react-native-windowspackage.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| vnext/Microsoft.ReactNative/Fabric/Composition/TextInput/WindowsTextInputComponentView.cpp | Fixes placeholder measurement sizing at non-100% scale (px→DIP) and repairs the default fontSize assignment when props are NaN. |
| change/react-native-windows-fix-textinput-placeholder-main.json | Records the patch-level change for release notes/versioning. |
acoates-ms
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Aug 3, 2026
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Change type from 'patch' to 'prerelease' for react-native-windows.
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Performance Test ResultsBranch: ❌ Regressions DetectedSectionList
✅ Passed147 scenario(s) across 27 suite(s) — no regressionsFlatList
TouchableOpacity
ScrollView
TouchableHighlight
Pressable
Modal
Image
ActivityIndicator
Switch
Button
TextInput
View
Text
SectionList.native-perf-test.ts
FlatList.native-perf-test.ts
TouchableHighlight.native-perf-test.ts
TouchableOpacity.native-perf-test.ts
Pressable.native-perf-test.ts
ScrollView.native-perf-test.ts
ActivityIndicator.native-perf-test.ts
TextInput.native-perf-test.ts
Switch.native-perf-test.ts
Button.native-perf-test.ts
Modal.native-perf-test.ts
Image.native-perf-test.ts
View.native-perf-test.ts
Text.native-perf-test.ts
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Forward-port of #16303 (which targets
0.83-stable) tomain, per @acoates-ms:Both defects are present on
maintoday, inWindowsTextInputComponentView::CreatePlaceholderLayout().1. Placeholder layout constraints were fed physical pixels, not DIPs
m_imgWidth/m_imgHeightare physical pixels (frame * pointScaleFactor), butfacebook::react::LayoutConstraintsare expressed in DIPs. The placeholder was therefore laid out inside a boxpointScaleFactorx too large, so it measured and positioned at a different height than the typed text — visible as the placeholder sitting at a different baseline than the value the user types, and worsening as scale increases.This version divides directly, with no
!= 0guard — per review feedback on #16303.LayoutMetrics::pointScaleFactorhas a default member initializer of1.0andEmptyLayoutMetricsonly designates.frame, so even the pre-layout sentinel inherits1.0; there is no path here where it is0.2. The NaN
fontSizeguard was a no-opThe guard evaluated
defaultTextAttributes().fontSizeas a discarded expression statement rather than assigning it, so a placeholder with no explicitfontSizenever actually picked up the default:if (std::isnan(props.textAttributes.fontSize)) { - facebook::react::TextAttributes::defaultTextAttributes().fontSize; + textAttributes.fontSize = facebook::react::TextAttributes::defaultTextAttributes().fontSize; }Testing
Verified on the
0.83-stableversion of this change (#16303): compiled into a framework source build (binary-gated) and re-probed in a production app at 250% scale — no regression, the NaN-fontSize guard now actually assigns (a no-fontSize placeholder renders at the default size), and placeholder-vs-typed are pixel-comparable at that geometry. Evidence attached to #16303.This
mainport is the identical change applied to the currentmainsource; it has not been separately run on-device, so CI is the gate here.Related: #16303 (
0.83-stable).Microsoft Reviewers: Open in CodeFlow