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fix: Unicode Text length Calculation#16219

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unicodemain
Open

fix: Unicode Text length Calculation#16219
vineethkuttan wants to merge 3 commits into
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unicodemain

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@vineethkuttan vineethkuttan commented Jun 5, 2026 •
edited by microsoft-github-policy-service Bot
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Description

The length of text that is being rendered is not calculated for Unicode characters, this change will fix it

Type of Change

  • Bug fix (non-breaking change which fixes an issue)

Why

Text Highlight for Unicode is not working

Screenshots

image

Testing

Tested in Playground

Changelog

Should this change be included in the release notes: yes

(fix: Unicode Text length Calculation)

Microsoft Reviewers: Open in CodeFlow

@vineethkuttan vineethkuttan requested a review from a team as a code owner June 5, 2026 05:26
protikbiswas100
protikbiswas100 reviewed Jun 5, 2026
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Comment thread vnext/Microsoft.ReactNative/Fabric/Composition/ParagraphComponentView.cpp Outdated
for (auto fragment : m_attributedStringBox.getValue().getFragments()) {
if (textPosition < fragment.string.length()) {
uint32_t utf16Length =
static_cast<uint32_t>(::Microsoft::Common::Unicode::Utf8ToUtf16Length(fragment.string));
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@protikbiswas100 protikbiswas100 Jun 5, 2026

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This change introduces Utf8ToUtf16Length, which can throw on conversion failure/overflow. It is now called from methods marked noexcept (eventEmitterAtPoint, IsTextSelectableAtPoint, RenderText, GetTextLayout). Any throw here would trigger terminate. Could we either make Utf8ToUtf16Length non-throwing for these call paths, or catch/fallback at callsites to avoid process termination?

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github-actions Bot commented Jun 5, 2026 •
edited
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Performance Test Results

Branch: unicodemain
Commit: 8f49e4f3
Time: 2026-06-05T06:40:26.819Z
Tests: 161/161 passed

✅ Passed

161 scenario(s) across 28 suite(s) — no regressions

SectionList

Scenario Mean Median StdDev Renders vs Baseline
SectionList mount 2.40ms 2.00ms ±0.52ms 1 -60.0%
SectionList unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
SectionList rerender 6.50ms 6.50ms ±1.18ms 2 -38.1%
SectionList with-3-sections-15-items 3.20ms 3.00ms ±0.63ms 1 -45.5%
SectionList with-5-sections-50-items 2.90ms 3.00ms ±0.57ms 1 -50.0%
SectionList with-10-sections-200-items 3.40ms 3.00ms ±1.43ms 1 -45.5%
SectionList with-20-sections-200-items 3.20ms 3.00ms ±0.92ms 1 -40.0%
SectionList with-section-separator 1.80ms 1.50ms ±1.23ms 1 -25.0%
SectionList with-item-separator 1.00ms 1.00ms ±0.00ms 1 -50.0%
SectionList with-header-footer 1.20ms 1.00ms ±0.42ms 1 -50.0%
SectionList with-section-footer 1.10ms 1.00ms ±0.32ms 1 -50.0%
SectionList with-sticky-section-headers 0.80ms 1.00ms ±0.42ms 1 -50.0%
SectionList with-empty-list 0.30ms 0.00ms ±0.48ms 1 -100.0%
SectionList with-50-sections-1000-items 1.20ms 1.00ms ±0.79ms 1 -50.0%

FlatList

Scenario Mean Median StdDev Renders vs Baseline
FlatList mount 2.50ms 2.00ms ±0.97ms 1 -50.0%
FlatList unmount 0.10ms 0.00ms ±0.32ms 0 +0.0%
FlatList rerender 5.50ms 5.00ms ±1.43ms 2 -44.4%
FlatList with-10-items 2.70ms 2.50ms ±1.34ms 1 -37.5%
FlatList with-100-items 2.80ms 3.00ms ±0.63ms 1 -40.0%
FlatList with-500-items 2.60ms 2.00ms ±0.84ms 1 -50.0%
FlatList with-1000-items 2.50ms 2.00ms ±0.71ms 1 -50.0%
FlatList horizontal 2.30ms 2.00ms ±0.82ms 1 -60.0%
FlatList with-separator 1.10ms 1.00ms ±0.32ms 1 -50.0%
FlatList with-header-footer 0.60ms 1.00ms ±0.52ms 1 -50.0%
FlatList with-empty-list 0.30ms 0.00ms ±0.48ms 1 -100.0%
FlatList with-get-item-layout 1.10ms 1.00ms ±1.45ms 1 +0.0%
FlatList inverted 0.90ms 1.00ms ±0.57ms 1 -33.3%
FlatList with-num-columns 1.80ms 1.50ms ±1.23ms 1 -50.0%

TouchableOpacity

Scenario Mean Median StdDev Renders vs Baseline
TouchableOpacity mount 0.40ms 0.00ms ±0.52ms 1 -100.0%
TouchableOpacity unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
TouchableOpacity rerender 0.80ms 1.00ms ±0.42ms 2 +0.0%
TouchableOpacity custom-active-opacity 0.40ms 0.00ms ±0.52ms 1 -100.0%
TouchableOpacity disabled 0.40ms 0.00ms ±0.52ms 1 -100.0%
TouchableOpacity with-all-handlers 0.40ms 0.00ms ±0.52ms 1 -100.0%
TouchableOpacity with-hit-slop 0.50ms 0.50ms ±0.53ms 1 -50.0%
TouchableOpacity with-delay 0.50ms 0.50ms ±0.53ms 1 -50.0%
TouchableOpacity nested 1.30ms 1.00ms ±0.95ms 1 +0.0%
TouchableOpacity multiple-10 2.80ms 3.00ms ±1.21ms 1 -50.0%
TouchableOpacity multiple-50 14.00ms 14.00ms ±2.39ms 1 -51.7%
TouchableOpacity multiple-100 10.93ms 11.00ms ±2.31ms 1 -78.0%

ScrollView

Scenario Mean Median StdDev Renders vs Baseline
ScrollView mount 0.20ms 0.00ms ±0.42ms 1 +0.0%
ScrollView unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
ScrollView rerender 0.30ms 0.00ms ±0.48ms 2 -100.0%
ScrollView children-20 1.53ms 2.00ms ±0.52ms 1 -50.0%
ScrollView children-100 9.13ms 9.00ms ±1.96ms 1 -43.8%
ScrollView horizontal 1.40ms 1.00ms ±0.52ms 1 -75.0%
ScrollView sticky-headers 1.90ms 2.00ms ±0.99ms 1 -33.3%
ScrollView scroll-indicators 0.50ms 0.50ms ±0.53ms 1 -50.0%
ScrollView nested 0.80ms 1.00ms ±0.63ms 1 +0.0%
ScrollView content-container-style 0.50ms 0.50ms ±0.53ms 1 -50.0%
ScrollView children-500 12.47ms 12.00ms ±2.39ms 1 -36.8%

TouchableHighlight

Scenario Mean Median StdDev Renders vs Baseline
TouchableHighlight mount 0.10ms 0.00ms ±0.32ms 1 -100.0%
TouchableHighlight unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
TouchableHighlight rerender 0.30ms 0.00ms ±0.48ms 2 -100.0%
TouchableHighlight custom-underlay-color 0.20ms 0.00ms ±0.42ms 1 +0.0%
TouchableHighlight custom-active-opacity 0.60ms 0.00ms ±0.97ms 1 +0.0%
TouchableHighlight disabled 0.20ms 0.00ms ±0.42ms 1 +0.0%
TouchableHighlight with-all-handlers 0.20ms 0.00ms ±0.42ms 1 +0.0%
TouchableHighlight with-hit-slop 0.10ms 0.00ms ±0.32ms 1 +0.0%
TouchableHighlight nested-touchables 0.50ms 0.50ms ±0.53ms 1 -50.0%
TouchableHighlight multiple-touchables-10 1.70ms 2.00ms ±0.48ms 1 -33.3%
TouchableHighlight multiple-touchables-50 6.20ms 6.00ms ±1.14ms 1 -52.0%
TouchableHighlight multiple-touchables-100 12.40ms 12.00ms ±1.51ms 1 -46.7%

Pressable

Scenario Mean Median StdDev Renders vs Baseline
Pressable mount 0.20ms 0.00ms ±0.42ms 1 +0.0%
Pressable unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Pressable rerender 0.20ms 0.00ms ±0.42ms 2 -100.0%
Pressable with-all-handlers 0.10ms 0.00ms ±0.32ms 1 +0.0%
Pressable with-style-function 0.20ms 0.00ms ±0.42ms 1 +0.0%
Pressable disabled 0.10ms 0.00ms ±0.32ms 1 +0.0%
Pressable with-hit-slop 0.10ms 0.00ms ±0.32ms 1 +0.0%
Pressable nested 0.30ms 0.00ms ±0.48ms 1 -100.0%
Pressable multiple-10 1.40ms 1.00ms ±0.51ms 1 -66.7%
Pressable multiple-50 7.87ms 8.00ms ±1.92ms 1 -42.9%
Pressable multiple-100 16.13ms 8.00ms ±27.62ms 1 -33.3%

Modal

Scenario Mean Median StdDev Renders vs Baseline
Modal mount 0.10ms 0.00ms ±0.32ms 1 +0.0%
Modal unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Modal rerender 0.20ms 0.00ms ±0.42ms 2 +0.0%
Modal slide-animation 0.20ms 0.00ms ±0.42ms 1 +0.0%
Modal fade-animation 0.20ms 0.00ms ±0.42ms 1 +0.0%
Modal transparent 0.20ms 0.00ms ±0.42ms 1 +0.0%
Modal with-callbacks 0.10ms 0.00ms ±0.32ms 1 +0.0%
Modal rich-content 0.90ms 1.00ms ±0.32ms 1 -50.0%
Modal with-accessibility 0.20ms 0.00ms ±0.42ms 1 +0.0%

Image

Scenario Mean Median StdDev Renders vs Baseline
Image mount 0.10ms 0.00ms ±0.32ms 1 +0.0%
Image unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Image rerender 0.00ms 0.00ms ±0.00ms 2 +0.0%
Image with-resize-mode 0.00ms 0.00ms ±0.00ms 1 +0.0%
Image with-border-radius 0.10ms 0.00ms ±0.32ms 1 +0.0%
Image with-tint-color 0.10ms 0.00ms ±0.32ms 1 +0.0%
Image with-blur-radius 0.00ms 0.00ms ±0.00ms 1 +0.0%
Image with-accessibility 0.10ms 0.00ms ±0.32ms 1 +0.0%
Image multiple-10 0.47ms 0.00ms ±0.64ms 1 -100.0%
Image multiple-50 1.93ms 2.00ms ±0.46ms 1 -33.3%
Image multiple-100 4.53ms 4.00ms ±1.51ms 1 -50.0%

ActivityIndicator

Scenario Mean Median StdDev Renders vs Baseline
ActivityIndicator mount 0.10ms 0.00ms ±0.32ms 1 +0.0%
ActivityIndicator unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
ActivityIndicator rerender 0.00ms 0.00ms ±0.00ms 2 +0.0%
ActivityIndicator size-large 0.10ms 0.00ms ±0.32ms 1 +0.0%
ActivityIndicator size-small 0.10ms 0.00ms ±0.32ms 1 +0.0%
ActivityIndicator with-color 0.10ms 0.00ms ±0.32ms 1 +0.0%
ActivityIndicator not-animating 0.00ms 0.00ms ±0.00ms 1 +0.0%
ActivityIndicator with-accessibility 0.10ms 0.00ms ±0.32ms 1 +0.0%
ActivityIndicator multiple-10 0.40ms 0.00ms ±0.51ms 1 -100.0%
ActivityIndicator multiple-50 2.20ms 2.00ms ±0.77ms 1 -50.0%
ActivityIndicator multiple-100 4.67ms 4.00ms ±0.90ms 1 -42.9%

Switch

Scenario Mean Median StdDev Renders vs Baseline
Switch mount 0.20ms 0.00ms ±0.42ms 1 +0.0%
Switch unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Switch rerender 0.30ms 0.00ms ±0.48ms 2 -100.0%
Switch value-true 0.00ms 0.00ms ±0.00ms 1 +0.0%
Switch disabled 0.10ms 0.00ms ±0.32ms 1 +0.0%
Switch custom-colors 0.20ms 0.00ms ±0.42ms 1 +0.0%
Switch on-value-change 0.10ms 0.00ms ±0.32ms 1 +0.0%
Switch with-accessibility 0.10ms 0.00ms ±0.32ms 1 +0.0%
Switch multiple-10 1.07ms 1.00ms ±0.46ms 1 -50.0%
Switch multiple-50 5.13ms 4.00ms ±2.03ms 1 -55.6%
Switch multiple-100 9.60ms 10.00ms ±2.10ms 1 -37.5%

Button

Scenario Mean Median StdDev Renders vs Baseline
Button mount 0.30ms 0.00ms ±0.48ms 1 -100.0%
Button unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Button rerender 0.50ms 0.50ms ±0.53ms 2 -50.0%
Button disabled 0.30ms 0.00ms ±0.48ms 1 -100.0%
Button with-color 0.30ms 0.00ms ±0.48ms 1 -100.0%
Button with-accessibility 0.60ms 0.00ms ±0.97ms 1 -100.0%
Button multiple-10 2.80ms 3.00ms ±0.77ms 1 -50.0%
Button multiple-50 11.53ms 13.00ms ±5.21ms 1 -51.9%
Button multiple-100 8.33ms 8.00ms ±2.06ms 1 -57.9%

TextInput

Scenario Mean Median StdDev Renders vs Baseline
TextInput mount 0.00ms 0.00ms ±0.00ms 1 +0.0%
TextInput unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
TextInput rerender 0.20ms 0.00ms ±0.42ms 2 +0.0%
TextInput multiline 0.10ms 0.00ms ±0.32ms 1 +0.0%
TextInput with-value 0.10ms 0.00ms ±0.32ms 1 +0.0%
TextInput styled 0.10ms 0.00ms ±0.32ms 1 +0.0%
TextInput multiple-100 4.67ms 4.00ms ±1.29ms 1 -42.9%

View

Scenario Mean Median StdDev Renders vs Baseline
View mount 0.00ms 0.00ms ±0.00ms 1 +0.0%
View unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
View rerender 0.00ms 0.00ms ±0.00ms 2 +0.0%
View nested-50 1.73ms 2.00ms ±0.46ms 1 -33.3%
View nested-100 4.53ms 4.00ms ±1.30ms 1 -42.9%
View shadow 0.00ms 0.00ms ±0.00ms 1 +0.0%
View border-radius 0.00ms 0.00ms ±0.00ms 1 +0.0%
View nested-500 10.13ms 7.00ms ±7.40ms 1 -30.0%

Text

Scenario Mean Median StdDev Renders vs Baseline
Text mount 0.10ms 0.00ms ±0.32ms 1 +0.0%
Text unmount 0.00ms 0.00ms ±0.00ms 0 +0.0%
Text rerender 0.00ms 0.00ms ±0.00ms 2 +0.0%
Text long-1000 0.00ms 0.00ms ±0.00ms 1 +0.0%
Text nested 0.10ms 0.00ms ±0.32ms 1 +0.0%
Text styled 0.10ms 0.00ms ±0.32ms 1 +0.0%
Text multiple-100 4.60ms 4.00ms ±1.68ms 1 -42.9%

SectionList.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
SectionList native mount 2.74ms 2.57ms ±0.62ms 1 -60.4%

FlatList.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
FlatList native mount 2.53ms 2.27ms ±0.72ms 1 -75.4%

TouchableHighlight.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
TouchableHighlight native mount 0.69ms 0.69ms ±0.04ms 1 -67.2%

TouchableOpacity.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
TouchableOpacity native mount 0.94ms 0.90ms ±0.11ms 1 -71.3%

Pressable.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Pressable native mount 0.75ms 0.71ms ±0.08ms 1 -71.8%

ScrollView.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
ScrollView native mount 1.69ms 1.65ms ±0.13ms 1 -59.3%

ActivityIndicator.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
ActivityIndicator native mount 0.83ms 0.64ms ±0.65ms 1 -74.2%

TextInput.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
TextInput native mount 1.00ms 0.97ms ±0.09ms 1 -76.2%

Switch.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Switch native mount 0.61ms 0.57ms ±0.10ms 1 -66.9%

Button.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Button native mount 0.86ms 0.86ms ±0.06ms 1 -67.1%

Modal.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Modal native mount 0.52ms 0.42ms ±0.30ms 1 -65.8%

Image.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Image native mount 1.04ms 0.90ms ±0.42ms 1 -60.4%

View.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
View native mount 0.54ms 0.52ms ±0.07ms 1 -63.9%

Text.native-perf-test.ts

Scenario Mean Median StdDev Renders vs Baseline
Text native mount 0.69ms 0.66ms ±0.10ms 1 -62.3%

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Nested Text components apply styles at wrong offsets when text contains multi-byte characters

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@vineethkuttan @protikbiswas100