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fix(textinput): correct placeholder layout constraints (px vs DIP) and no-op NaN fontSize guard #16303

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fix(textinput): correct placeholder layout constraints (px vs DIP) and no-op NaN fontSize guard #16303

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fix(textinput): correct placeholder layout size and default font size
FaithfulAudio Jul 11, 2026
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FaithfulAudio Jul 11, 2026
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7 changes: 7 additions & 0 deletions change/react-native-windows-fix-textinput-placeholder.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
{
"type": "patch",
"comment": "Fix placeholder layout constraints fed physical px instead of DIPs; fix no-op NaN fontSize guard in CreatePlaceholderLayout",
"packageName": "react-native-windows",
"email": "collindanielschneide@gmail.com",
"dependentChangeType": "patch"
}
11 changes: 8 additions & 3 deletions vnext/Microsoft.ReactNative/Fabric/Composition/TextInput/WindowsTextInputComponentView.cpp
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Expand Up @@ -1690,16 +1690,21 @@ winrt::com_ptr<::IDWriteTextLayout> WindowsTextInputComponentView::CreatePlaceho
const auto &props = windowsTextInputProps();
facebook::react::TextAttributes textAttributes = props.textAttributes;
if (std::isnan(props.textAttributes.fontSize)) {
facebook::react::TextAttributes::defaultTextAttributes().fontSize;
textAttributes.fontSize = facebook::react::TextAttributes::defaultTextAttributes().fontSize;
}
textAttributes.fontSizeMultiplier = m_fontSizeMultiplier;
fragment1.string = props.placeholder;
fragment1.textAttributes = textAttributes;
attributedString.appendFragment(std::move(fragment1));

facebook::react::LayoutConstraints constraints;
constraints.maximumSize.width = static_cast<FLOAT>(m_imgWidth);
constraints.maximumSize.height = static_cast<FLOAT>(m_imgHeight);
// m_imgWidth/m_imgHeight are physical pixels (frame * pointScaleFactor), but
// LayoutConstraints are expressed in DIPs. Feeding physical px laid the
// placeholder out in a box pointScaleFactor x too large, so the placeholder was
// measured/positioned at a different height than the typed text. Convert to DIPs.
const float scale = m_layoutMetrics.pointScaleFactor != 0.0f ? m_layoutMetrics.pointScaleFactor : 1.0f;

@acoates-ms acoates-ms Jul 16, 2026

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I dont think we should need the != 0 protection here -- unless that is something you saw?

@FaithfulAudio FaithfulAudio Jul 16, 2026

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You're right — no, we didn't see it hit zero; that was purely defensive around the new division. LayoutMetrics::pointScaleFactor has a default member initializer of 1.0, and EmptyLayoutMetrics only designates .frame, so even the pre-layout sentinel inherits 1.0 — there's no normal path where it's 0 here. I'll drop the guard and just divide by m_layoutMetrics.pointScaleFactor.

constraints.maximumSize.width = static_cast<FLOAT>(m_imgWidth) / scale;
constraints.maximumSize.height = static_cast<FLOAT>(m_imgHeight) / scale;

facebook::react::WindowsTextLayoutManager::GetTextLayout(
facebook::react::AttributedStringBox(attributedString), {} /*TODO*/, constraints, textLayout);
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