feat(TextBox): spellchecking #22383

ramezgerges · 2026-01-18T14:24:16Z

GitHub Issue: closes https://github.com/unoplatform/kahua-private/issues/398

PR Type:

What is the current behavior? 🤔

What is the new behavior? 🚀

PR Checklist ✅

Please check if your PR fulfills the following requirements:

📝 Commits must be following the Conventional Commits specification.
🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
📚 Docs have been added/updated which fit documentation template (for bug fixes / features)
🖼️ Validated PR Screenshots Compare Test Run results.
❗ Contains NO breaking changes

Other information ℹ️

Copilot

Pull request overview

This pull request adds spellchecking functionality to the TextBox control for Skia-based platforms. It implements spell checking using the WeCantSpell.Hunspell library with an embedded US English dictionary, provides visual feedback via red wavy underlines, and integrates spell check suggestions into the context menu.

Changes:

Adds Hunspell-based spell checking to UnicodeText rendering with embedded US English dictionary
Integrates spell check suggestions into TextBox context menu
Provides FeatureConfiguration API for custom dictionaries
Adds localized resource strings for spell check UI across 100+ languages

Reviewed changes

Copilot reviewed 95 out of 96 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
src/Uno.UI/Uno.UI.Skia.csproj	Adds WeCantSpell.Hunspell package reference and embeds dictionary files
src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs	Core spell checking implementation with word detection, dictionary lookup, visual rendering, and suggestion generation
src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.skia.cs	Wires IsSpellCheckEnabled property to DisplayBlock
src/Uno.UI/UI/Xaml/Controls/TextBox/TextBoxView.skia.cs	Initializes spell check state on DisplayBlock
src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.pointers.skia.cs	Adds spell check suggestions to context menu
src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.skia.cs	Passes spell check flag to UnicodeText constructor
src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.cs	Optimizes selection change handling
src/Uno.UI/FeatureConfiguration.cs	Adds CustomSpellCheckDictionaries configuration API
src/Uno.UI/Resources/en_US.aff	Hunspell affix rules for English
src/Uno.UI/Resources/en_US.dic	Embedded US English dictionary (~49K words)
src/Uno.UI/UI/Xaml/Controls/WinUIResources/*	Adds "Spelling" localized strings for 100+ languages

src/Uno.UI/FeatureConfiguration.cs

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

src/Uno.UI/FeatureConfiguration.cs

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

src/Uno.UI/Uno.UI.Skia.csproj

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

unodevops · 2026-01-18T14:43:07Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22383/wasm-skia-net9/index.html

unodevops · 2026-01-18T14:50:54Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22383/docs/index.html

unodevops · 2026-01-18T18:10:58Z

⚠️⚠️ The build 191690 has failed on Uno.UI - CI.

unodevops · 2026-01-22T18:42:00Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22383/docs/index.html

unodevops · 2026-01-22T18:42:51Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22383/wasm-skia-net9/index.html

Copilot

Pull request overview

Copilot reviewed 95 out of 96 changed files in this pull request and generated 6 comments.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-01-22T20:57:09Z

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

+	private static List<WordList> GetWordLists()
+	{
+		var wordLists = new List<WordList>();
+		var assembly = Assembly.GetAssembly(typeof(UnicodeText))!;
+		var enAff = assembly.GetManifestResourceNames().First(r => r.Contains("en_US.aff"));
+		var enDic = assembly.GetManifestResourceNames().First(r => r.Contains("en_US.dic"));
+		wordLists.Add(WordList.CreateFromStreams(assembly.GetManifestResourceStream(enDic), assembly.GetManifestResourceStream(enAff)));
+
+		if (FeatureConfiguration.TextBox.CustomSpellCheckDictionaries is { } dictionaries)
+		{
+			foreach (var (dic, aff) in dictionaries)
+			{
+				if (aff != null)
+				{
+					try
+					{
+						wordLists.Add(WordList.CreateFromStreams(dic, aff));
+					}
+					catch (Exception e)
+					{
+						if (typeof(UnicodeText).Log().IsEnabled(LogLevel.Error))
+						{
+							typeof(UnicodeText).Log().Error($"Failed to load dictionary", e);
+						}
+					}
+				}
+			}
+		}
+
+		return wordLists;
+	}


The GetWordLists method loads and parses dictionary files each time it's called, which is an expensive operation. Since _wordLists is a static field shared across all UnicodeText instances, this creates a potential memory issue where dictionaries are loaded multiple times unnecessarily if _wordLists is set to null or garbage collected. Additionally, the embedded en_US.dic file has 49,570 lines which will consume significant memory. Consider implementing proper singleton pattern or caching to ensure dictionaries are only loaded once per application lifetime.

Copilot · 2026-01-22T20:57:09Z

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

+			foreach (var (dic, aff) in dictionaries)
+			{
+				if (aff != null)
+				{
+					try
+					{
+						wordLists.Add(WordList.CreateFromStreams(dic, aff));


The CustomSpellCheckDictionaries property allows streams to be provided but there's no check that 'dic' is not null before passing it to CreateFromStreams. Only 'aff' is checked for null. This asymmetry could lead to a NullReferenceException if a user provides a null dictionary stream. Either check both for null or document that 'dic' must not be null.

Copilot · 2026-01-22T20:57:09Z

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

+								var correctionClusterStart = _textIndexToGlyph[Math.Max(wordStart + correction.Value.correctionStart, runStartIndex)];
+								var correctionClusterEnd = _textIndexToGlyph[Math.Min(wordStart + correction.Value.correctionEnd, runEndIndex) - 1]; // -1 because the end is exclusive for boundaries but inclusive for glyph map


The spell-check drawing logic accesses _textIndexToGlyph array at indices calculated from word boundaries and corrections, but there's no bounds checking. If wordStart + correction.Value.correctionStart or wordStart + correction.Value.correctionEnd exceed the text length or fall outside valid indices, this will cause an IndexOutOfRangeException. Add bounds validation before array access.

Copilot · 2026-01-22T20:57:10Z

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

+		var assembly = Assembly.GetAssembly(typeof(UnicodeText))!;
+		var enAff = assembly.GetManifestResourceNames().First(r => r.Contains("en_US.aff"));
+		var enDic = assembly.GetManifestResourceNames().First(r => r.Contains("en_US.dic"));
+		wordLists.Add(WordList.CreateFromStreams(assembly.GetManifestResourceStream(enDic), assembly.GetManifestResourceStream(enAff)));


The GetManifestResourceStream method can return null if the resource is not found, but the code passes the result directly to WordList.CreateFromStreams without null checking. This could cause a NullReferenceException. Add null checks for both stream retrievals before calling CreateFromStreams.

Copilot · 2026-01-22T20:57:10Z

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.pointers.skia.cs

+		var text = Text;
+		var newText = text[..correctionStart] + suggestion + text[correctionEnd..];
+		Text = newText;
+		Select(correctionStart + suggestion.Length, 0);


The ReplaceWithSuggestion method doesn't validate that correctionStart and correctionEnd are within bounds of the text. If the text has changed between when the context menu was opened and when the suggestion is clicked, this could cause an ArgumentOutOfRangeException. Add bounds validation before attempting to slice the string.

Suggested change

var text = Text;

var newText = text[..correctionStart] + suggestion + text[correctionEnd..];

Text = newText;

Select(correctionStart + suggestion.Length, 0);

var text = Text ?? string.Empty;

// Ensure correction range is valid for the current text to avoid ArgumentOutOfRangeException

if (correctionStart < 0 ||

correctionEnd < correctionStart ||

correctionStart > text.Length ||

correctionEnd > text.Length)

{

return;

}

suggestion ??= string.Empty;

var newText = text[..correctionStart] + suggestion + text[correctionEnd..];

Text = newText;

var caretIndex = Math.Min(correctionStart + suggestion.Length, newText.Length);

Select(caretIndex, 0);

Copilot · 2026-01-22T20:57:10Z

src/Uno.UI/UI/Xaml/Documents/UnicodeText.skia.cs

+	private static List<(int correctionStart, int correctionEnd)?> GetSpellCheckSuggestions(List<int> wordBoundaries, string text)
+	{
+		var ret = new List<(int correctionStart, int correctionEnd)?>();
+		var start = 0;
+		foreach (var end in wordBoundaries)
+		{
+			var word = text.Substring(start, end - start);
+			var startTrimmedWord = word.TrimStart();
+			var trimmedWord = startTrimmedWord.TrimEnd();
+
+			_wordLists ??= GetWordLists();
+
+			if (trimmedWord.Length > 0 && !trimmedWord.Any(c => char.IsPunctuation(c) || char.IsNumber(c) || char.IsSeparator(c) || char.IsWhiteSpace(c) || char.IsSymbol(c)))
+			{
+				if (_wordLists.Any(wordList => wordList.Check(trimmedWord)))
+				{
+					ret.Add(null);
+				}
+				else
+				{
+					var correctionStart = word.Length - startTrimmedWord.Length;
+					var correctionEnd = word.Length - startTrimmedWord.Length + trimmedWord.Length;
+					ret.Add((correctionStart, correctionEnd));
+				}
+			}
+			else
+			{
+				ret.Add(null);
+			}
+
+			start = end;
+		}
+
+		return ret;
+	}


The GetSpellCheckSuggestions method is called during text layout for every word in the text, which could be a performance bottleneck for large text content. Each word requires dictionary lookups via wordList.Check() which may be expensive. Consider adding a cache for frequently-checked words or deferring spell checking to an async background operation, especially for long documents.

unodevops · 2026-01-22T21:05:55Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22383/wasm-skia-net9/index.html

unodevops · 2026-01-22T21:13:22Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22383/docs/index.html

unodevops · 2026-01-23T00:11:13Z

⚠️⚠️ The build 192632 has failed on Uno.UI - CI.

…ubleTapped

…Text

unodevops · 2026-01-24T00:50:20Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22383/wasm-skia-net9/index.html

unodevops · 2026-01-24T00:52:08Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22383/docs/index.html

unodevops · 2026-01-24T03:14:29Z

⚠️⚠️ The build 192852 has failed on Uno.UI - CI.

Copilot AI review requested due to automatic review settings January 18, 2026 14:24

github-actions bot added the area/skia ✏️ Categorizes an issue or PR as relevant to Skia label Jan 18, 2026

Copilot started reviewing on behalf of ramezgerges January 18, 2026 14:24 View session

Copilot AI reviewed Jan 18, 2026

View reviewed changes

github-actions bot assigned ramezgerges Jan 22, 2026

ramezgerges added 15 commits January 22, 2026 15:46

chore: GetWordsAt

ee7f79f

chore: hunspell setup

d8f082b

chore: squiggly line rendering

336ec53

chore: squiggly line rendering 2

581051a

chore: squiggly line rendering 3

315d237

chore: squiggly line rendering 4

ff96725

chore: squiggly line rendering 5

8e21b23

chore: avoid unnecessary invalidation

9e8c256

chore: scale spellcheck underlining with font size

6d75a14

chore: context menu

831a453

chore: localization

6788989

chore: embed english dictionary for spellchecking

53d7479

chore: support multiple dictionaries

4928f81

chore: typo

fcd3f9a

chore: avoid extra allocations when spellcheck is disabled

863de7a

Copilot AI review requested due to automatic review settings January 22, 2026 20:46

ramezgerges force-pushed the spellchecking branch from 2279791 to 863de7a Compare January 22, 2026 20:46

Copilot started reviewing on behalf of ramezgerges January 22, 2026 20:46 View session

Copilot AI reviewed Jan 22, 2026

View reviewed changes

ramezgerges mentioned this pull request Jan 23, 2026

Text highlighters #22448

Draft

ramezgerges added 5 commits January 23, 2026 14:32

chore: adjust When_IsTextSelectionEnabled_Chunking_DoubleTapped

4b7355d

chore: fix word splitting for When_IsTextSelectionEnabled_Chunking_Do…

14a707d

…ubleTapped

chore: fix When_IsTextSelectionEnabled_TouchScroll_Then_DoesNotSelect…

13f302b

…Text

chore: fix When_Multiline_Keyboard_Chunking

9949355

chore: make When_Pointer_RightClick_Selection more stable

894d125

		var correctionClusterStart = _textIndexToGlyph[Math.Max(wordStart + correction.Value.correctionStart, runStartIndex)];
		var correctionClusterEnd = _textIndexToGlyph[Math.Min(wordStart + correction.Value.correctionEnd, runEndIndex) - 1]; // -1 because the end is exclusive for boundaries but inclusive for glyph map

-		var text = Text;
-		var newText = text[..correctionStart] + suggestion + text[correctionEnd..];
-		Text = newText;
-		Select(correctionStart + suggestion.Length, 0);
+		var text = Text ?? string.Empty;
+		// Ensure correction range is valid for the current text to avoid ArgumentOutOfRangeException
+		if (correctionStart < 0 ||
+			correctionEnd < correctionStart ||
+			correctionStart > text.Length ||
+			correctionEnd > text.Length)
+		{
+			return;
+		}
+		suggestion ??= string.Empty;
+		var newText = text[..correctionStart] + suggestion + text[correctionEnd..];
+		Text = newText;
+		var caretIndex = Math.Min(correctionStart + suggestion.Length, newText.Length);
+		Select(caretIndex, 0);

feat(TextBox): spellchecking #22383

Are you sure you want to change the base?

feat(TextBox): spellchecking #22383

Conversation

ramezgerges commented Jan 18, 2026

PR Type:

What is the current behavior? 🤔

What is the new behavior? 🚀

PR Checklist ✅

Other information ℹ️

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

unodevops commented Jan 18, 2026

Uh oh!

unodevops commented Jan 18, 2026

Uh oh!

unodevops commented Jan 18, 2026

Uh oh!

unodevops commented Jan 22, 2026

Uh oh!

unodevops commented Jan 22, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 22, 2026

Choose a reason for hiding this comment

Uh oh!

unodevops commented Jan 22, 2026

Uh oh!

unodevops commented Jan 22, 2026

Uh oh!

unodevops commented Jan 23, 2026

Uh oh!

unodevops commented Jan 24, 2026

Uh oh!

unodevops commented Jan 24, 2026

Uh oh!

unodevops commented Jan 24, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants