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Address performance problems for StructuredText code blocks #8

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Merged
bisonbet merged 2 commits into from
Jun 1, 2026
Merged

Address performance problems for StructuredText code blocks #8

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d444000
Convert code to owned string before async tokenisation
danielrothmann Mar 15, 2026
4b284b3
Skip code tokenisation if there is no theme to apply
danielrothmann Mar 15, 2026
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17 changes: 9 additions & 8 deletions Sources/Textual/Internal/Highlighter/HighlightedTextFragment.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -29,13 +29,13 @@ struct HighlightedTextFragment: View {
}

var body: some View {
// Convert to an owned String before the async boundary
let code = String(content.characters[...])

TextFragment(model.highlightedCode ?? AttributedString(content))
.foregroundStyle(theme.foregroundColor)
.task(id: content) {
await model.tokenize(
content: content,
languageHint: languageHint
)
.task(id: code) {
await model.tokenize(code: code, languageHint: languageHint, theme: theme)
Comment on lines +37 to +38

@chatgpt-codex-connector chatgpt-codex-connector Bot May 30, 2026

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P2 Badge Include highlighter theme in tokenization task identity

When a code block is first rendered with .plain or another theme whose tokenProperties is empty, tokenize now intentionally skips Prism and stores only a single plain token; if the same view later receives a syntax-highlighting theme for the same code string, this .task(id: code) does not run again, so the block stays un-tokenized and cannot apply token colors. This affects apps that switch themes dynamically via highlighterTheme(_:); key the task on the tokenization inputs that now include the theme/tokenProperties (or otherwise retrigger tokenization when an empty-token theme changes to a highlighting theme).

Useful? React with 👍 / 👎.

}
.onChange(of: Tuple(model.tokens, textEnvironment)) { _, newValue in
model.highlight(
Expand All @@ -53,11 +53,12 @@ extension HighlightedTextFragment {
var tokens: [CodeToken] = []
var highlightedCode: AttributedString?

func tokenize(content: AttributedSubstring, languageHint: String?) async {
let code = String(content.characters[...])
func tokenize(code: String, languageHint: String?, theme: StructuredText.HighlighterTheme) async {
tokens = [CodeToken(content: code, type: .plain)]

if let tokenizer = CodeTokenizer.shared, let languageHint {
// Skip the expensive tokenizer when the theme has no token properties
if !theme.tokenProperties.isEmpty,
let tokenizer = CodeTokenizer.shared, let languageHint {
tokens = await tokenizer.tokenize(code: code, language: languageHint)
}
}
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