TASK-049: C/C++ highlighting and multi-line comment coloring

Adds a CPP language, preprocessor coloring, hex and digit-separator numbers, and block-comment state carried across lines. CodeBlock now highlights a file once instead of on every recomposition. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
2026-09-28 13:17:33 +09:00 · 2026-09-28 13:17:33 +09:00 · 10b38a3ac4
commit 10b38a3ac4
parent d9536289e9
5 changed files with 400 additions and 27 deletions
--- a/app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/CodeBrowserScreen.kt
+++ b/app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/CodeBrowserScreen.kt
@ -87,7 +87,7 @@ import com.ubisam.ubgitea.domain.model.TreeEntryType
 import com.ubisam.ubgitea.feature.codebrowser.content.CodeSyntaxColors
 import com.ubisam.ubgitea.feature.codebrowser.content.ContentClassification
 import com.ubisam.ubgitea.feature.codebrowser.content.SyntaxLanguage
-import com.ubisam.ubgitea.feature.codebrowser.content.highlightLine
+import com.ubisam.ubgitea.feature.codebrowser.content.highlightLines
 import com.ubisam.ubgitea.feature.codebrowser.content.rememberCodeSyntaxColors
 import com.ubisam.ubgitea.feature.codebrowser.content.syntaxLanguageForPath
 import java.io.File
@ -308,16 +308,18 @@ private fun FileContent(
 private fun CodeBlock(text: String, language: SyntaxLanguage, wordWrap: Boolean, modifier: Modifier = Modifier) {
    val colors = rememberCodeSyntaxColors()
    val lines = remember(text) { text.split("\n") }
+    // Whole-file, once per file: block comments carry state across lines (see tokenizeLines).
+    val highlighted = remember(lines, language, colors) { highlightLines(lines, language, colors) }
    val lineNumberWidth = remember(lines.size) { lines.size.toString().length }
    val gutterWidth = (lineNumberWidth * 8 + 12).dp
    SelectionContainer(modifier = modifier) {
        if (wordWrap) {
            Column(Modifier.fillMaxSize().verticalScroll(rememberScrollState())) {
-                lines.forEachIndexed { index, line ->
+                highlighted.forEachIndexed { index, line ->
                    Row(Modifier.fillMaxWidth()) {
                        LineNumber(index, gutterWidth, colors)
                        Text(
-                            text = highlightLine(line, language, colors),
+                            text = line,
                            fontFamily = FontFamily.Monospace,
                            fontSize = 13.sp,
                            color = colors.text,
@ -333,9 +335,9 @@ private fun CodeBlock(text: String, language: SyntaxLanguage, wordWrap: Boolean,
                    lines.indices.forEach { index -> LineNumber(index, gutterWidth, colors) }
                }
                Column(Modifier.horizontalScroll(rememberScrollState())) {
-                    lines.forEach { line ->
+                    highlighted.forEach { line ->
                        Text(
-                            text = highlightLine(line, language, colors),
+                            text = line,
                            fontFamily = FontFamily.Monospace,
                            fontSize = 13.sp,
                            color = colors.text,
--- a/app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighter.kt
+++ b/app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighter.kt
@ -12,18 +12,18 @@ import androidx.compose.ui.text.withStyle
 import com.ubisam.ubgitea.domain.model.RepositoryPath

 /**
- * A deliberately lightweight, regex-based highlighter -- not a real per-language parser. Each line
- * is tokenized independently with no cross-line state, so a `/* ... */` block comment or a
- * triple-quoted string that spans multiple lines is only colored correctly on the line(s) where it
- * actually starts and ends, not on every line in between. A real tokenizer for every language this
- * app might show source from would be a much larger undertaking than this file viewer needs; this
- * covers the common, single-line case (which is the vast majority of real code) at a fraction of the
- * cost, matching this codebase's established preference for hand-rolled solutions over new
- * dependencies (see the launcher icon's and the favorite-push logo's own comments on the same
- * point).
+ * A deliberately lightweight, regex-based highlighter -- not a real per-language parser. Lines are
+ * tokenized one at a time; the only state carried from one line to the next is "still inside a
+ * block comment" (see [tokenizeLines]), so a multi-line `/* ... */` or `<!-- ... -->` comment is
+ * colored on every line it covers. A string that spans multiple lines (C++ raw strings, C# verbatim
+ * strings, Python triple quotes) is still only colored on the line where it starts. A real
+ * tokenizer for every language this app might show source from would be a much larger undertaking
+ * than this file viewer needs; this covers the common cases at a fraction of the cost, matching
+ * this codebase's established preference for hand-rolled solutions over new dependencies (see the
+ * launcher icon's and the favorite-push logo's own comments on the same point).
 */
 enum class SyntaxLanguage {
-    KOTLIN, JAVA, CSHARP, JAVASCRIPT, PYTHON, SHELL, YAML, XML, JSON, CSS, SQL, PLAIN
+    KOTLIN, JAVA, CSHARP, CPP, JAVASCRIPT, PYTHON, SHELL, YAML, XML, JSON, CSS, SQL, PLAIN
 }

 fun syntaxLanguageForPath(path: RepositoryPath): SyntaxLanguage {
@ -32,6 +32,7 @@ fun syntaxLanguageForPath(path: RepositoryPath): SyntaxLanguage {
        "kt", "kts" -> SyntaxLanguage.KOTLIN
        "java" -> SyntaxLanguage.JAVA
        "cs" -> SyntaxLanguage.CSHARP
+        "c", "h", "cc", "cpp", "cxx", "hpp", "hh", "hxx", "inl", "ipp" -> SyntaxLanguage.CPP
        "js", "jsx", "mjs", "ts", "tsx" -> SyntaxLanguage.JAVASCRIPT
        "py" -> SyntaxLanguage.PYTHON
        "sh", "bash", "zsh" -> SyntaxLanguage.SHELL
@ -50,6 +51,7 @@ data class CodeSyntaxColors(
    val string: Color,
    val comment: Color,
    val number: Color,
+    val preprocessor: Color,
 )

 // Colors are fixed (not derived from the app's own sky-blue Material theme) and only switch
@ -67,6 +69,7 @@ fun rememberCodeSyntaxColors(): CodeSyntaxColors {
                string = Color(0xFFCE9178),
                comment = Color(0xFF6A9955),
                number = Color(0xFFB5CEA8),
+                preprocessor = Color(0xFF9B9B9B),
            )
        } else {
            CodeSyntaxColors(
@ -75,6 +78,7 @@ fun rememberCodeSyntaxColors(): CodeSyntaxColors {
                string = Color(0xFFA31515),
                comment = Color(0xFF008000),
                number = Color(0xFF098658),
+                preprocessor = Color(0xFF6B6B6B),
            )
        }
    }
@ -86,6 +90,7 @@ private data class LangSpec(
    val lineComment: String? = null,
    val blockComment: Boolean = false,
    val xmlComment: Boolean = false,
+    val preprocessor: Boolean = false,
 )

 private val SPECS: Map<SyntaxLanguage, LangSpec> = mapOf(
@ -127,6 +132,25 @@ private val SPECS: Map<SyntaxLanguage, LangSpec> = mapOf(
        ),
        lineComment = "//",
        blockComment = true,
+        preprocessor = true,
+    ),
+    SyntaxLanguage.CPP to LangSpec(
+        keywords = setOf(
+            "alignas", "alignof", "auto", "bool", "break", "case", "catch", "char", "char8_t",
+            "char16_t", "char32_t", "class", "concept", "const", "consteval", "constexpr",
+            "constinit", "const_cast", "continue", "co_await", "co_return", "co_yield", "decltype",
+            "default", "delete", "do", "double", "dynamic_cast", "else", "enum", "explicit",
+            "export", "extern", "false", "final", "float", "for", "friend", "goto", "if", "inline",
+            "int", "long", "mutable", "namespace", "new", "noexcept", "nullptr", "operator",
+            "override", "private", "protected", "public", "register", "reinterpret_cast",
+            "requires", "return", "short", "signed", "sizeof", "static", "static_assert",
+            "static_cast", "struct", "switch", "template", "this", "thread_local", "throw", "true",
+            "try", "typedef", "typeid", "typename", "union", "unsigned", "using", "virtual", "void",
+            "volatile", "wchar_t", "while",
+        ),
+        lineComment = "//",
+        blockComment = true,
+        preprocessor = true,
    ),
    SyntaxLanguage.JAVASCRIPT to LangSpec(
        keywords = setOf(
@ -181,9 +205,13 @@ private val SPECS: Map<SyntaxLanguage, LangSpec> = mapOf(
 private val STRING_OR_NUMBER_OR_WORD =
    "\"(?:[^\"\\\\]|\\\\.)*\"" + "|" +
        "'(?:[^'\\\\]|\\\\.)*'" + "|" +
-        "\\b\\d+(?:\\.\\d+)?[a-zA-Z]?\\b" + "|" +
+        // Hex, and decimal with digit separators (C#/Kotlin/Java `30_000`, C++ `1'000'000`).
+        "\\b(?:0[xX][0-9a-fA-F_']+|\\d[\\d_']*(?:\\.\\d+)?(?:[eE][+-]?\\d+)?)[a-zA-Z]*\\b" + "|" +
        "\\b[A-Za-z_][A-Za-z0-9_]*\\b"

+private val PREPROCESSOR_DIRECTIVE = Regex("^\\s*#\\s*[A-Za-z_]+")
+private val INCLUDE_TARGET = Regex("^\\s*<[^>]*>")
+
 private val patternCache: Map<SyntaxLanguage, Regex> = SPECS.mapValues { (_, spec) ->
    val parts = mutableListOf<String>()
    if (spec.blockComment) parts += "/\\*.*?\\*/|/\\*.*$"
@ -193,27 +221,94 @@ private val patternCache: Map<SyntaxLanguage, Regex> = SPECS.mapValues { (_, spe
    Regex(parts.joinToString("|"))
 }

-fun highlightLine(line: String, language: SyntaxLanguage, colors: CodeSyntaxColors): AnnotatedString {
+/** One colored stretch of a line: `[start, end)` in that line's own character offsets. */
+internal data class SyntaxToken(val start: Int, val end: Int, val role: TokenRole)
+
+private enum class BlockComment(val open: String, val close: String) {
+    C_STYLE("/*", "*/"),
+    XML("<!--", "-->"),
+}
+
+/**
+ * Tokenizes a whole file, carrying "still inside a block comment" from each line to the next. Kept
+ * free of Compose types so it can be unit-tested directly.
+ */
+internal fun tokenizeLines(lines: List<String>, language: SyntaxLanguage): List<List<SyntaxToken>> {
    val spec = SPECS.getValue(language)
    val pattern = patternCache.getValue(language)
-    return buildAnnotatedString {
-        var lastIndex = 0
-        for (match in pattern.findAll(line)) {
-            if (match.range.first > lastIndex) append(line.substring(lastIndex, match.range.first))
-            val text = match.value
-            val style = classify(text, spec)?.let { role -> SpanStyle(color = role.colorOf(colors), fontWeight = role.weight) }
-            if (style != null) withStyle(style) { append(text) } else append(text)
-            lastIndex = match.range.last + 1
+    var open: BlockComment? = null
+    return lines.map { line ->
+        val tokens = mutableListOf<SyntaxToken>()
+        var from = 0
+        open?.let { block ->
+            val close = line.indexOf(block.close)
+            if (close < 0) {
+                if (line.isNotEmpty()) tokens += SyntaxToken(0, line.length, TokenRole.COMMENT)
+                return@map tokens
+            }
+            from = close + block.close.length
+            tokens += SyntaxToken(0, from, TokenRole.COMMENT)
+            open = null
        }
-        if (lastIndex < line.length) append(line.substring(lastIndex))
+        if (from == 0 && spec.preprocessor) {
+            PREPROCESSOR_DIRECTIVE.find(line)?.let { directive ->
+                tokens += SyntaxToken(directive.range.first, directive.range.last + 1, TokenRole.PREPROCESSOR)
+                from = directive.range.last + 1
+                if (directive.value.endsWith("include") || directive.value.endsWith("import")) {
+                    INCLUDE_TARGET.find(line.substring(from))?.let { target ->
+                        tokens += SyntaxToken(from + target.range.first, from + target.range.last + 1, TokenRole.STRING)
+                        from += target.range.last + 1
+                    }
+                }
+            }
+        }
+        for (match in pattern.findAll(line, from)) {
+            val text = match.value
+            val role = classify(text, spec) ?: continue
+            tokens += SyntaxToken(match.range.first, match.range.last + 1, role)
+            if (role == TokenRole.COMMENT) open = unterminatedBlockComment(text, spec)
+        }
+        tokens
    }
 }

-private enum class TokenRole(val weight: FontWeight?) {
+private fun unterminatedBlockComment(text: String, spec: LangSpec): BlockComment? {
+    val block = when {
+        spec.blockComment && text.startsWith(BlockComment.C_STYLE.open) -> BlockComment.C_STYLE
+        spec.xmlComment && text.startsWith(BlockComment.XML.open) -> BlockComment.XML
+        else -> return null
+    }
+    // "/*/" opens a comment without closing it: the close must come after the open delimiter.
+    val closed = text.length >= block.open.length + block.close.length && text.endsWith(block.close)
+    return if (closed) null else block
+}
+
+/** Highlights a whole file at once, so multi-line comments are colored on every line. */
+fun highlightLines(lines: List<String>, language: SyntaxLanguage, colors: CodeSyntaxColors): List<AnnotatedString> =
+    tokenizeLines(lines, language).mapIndexed { index, tokens -> annotate(lines[index], tokens, colors) }
+
+fun highlightLine(line: String, language: SyntaxLanguage, colors: CodeSyntaxColors): AnnotatedString =
+    highlightLines(listOf(line), language, colors).single()
+
+private fun annotate(line: String, tokens: List<SyntaxToken>, colors: CodeSyntaxColors): AnnotatedString =
+    buildAnnotatedString {
+        var lastIndex = 0
+        for (token in tokens) {
+            if (token.start > lastIndex) append(line.substring(lastIndex, token.start))
+            withStyle(SpanStyle(color = token.role.colorOf(colors), fontWeight = token.role.weight)) {
+                append(line.substring(token.start, token.end))
+            }
+            lastIndex = token.end
+        }
+        if (lastIndex < line.length) append(line.substring(lastIndex))
+    }
+
+internal enum class TokenRole(val weight: FontWeight?) {
    COMMENT(null),
    STRING(null),
    NUMBER(null),
    KEYWORD(FontWeight.SemiBold),
+    PREPROCESSOR(null),
    ;

    fun colorOf(colors: CodeSyntaxColors): Color = when (this) {
@ -221,6 +316,7 @@ private enum class TokenRole(val weight: FontWeight?) {
        STRING -> colors.string
        NUMBER -> colors.number
        KEYWORD -> colors.keyword
+        PREPROCESSOR -> colors.preprocessor
    }
 }

--- a/app/src/test/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighterTest.kt
+++ b/app/src/test/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighterTest.kt
@ -0,0 +1,176 @@
+package com.ubisam.ubgitea.feature.codebrowser.content
+
+import com.ubisam.ubgitea.domain.model.RepositoryPath
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class SyntaxHighlighterTest {
+    private fun tokens(language: SyntaxLanguage, vararg lines: String): List<List<Pair<String, TokenRole>>> =
+        tokenizeLines(lines.toList(), language).mapIndexed { index, line ->
+            line.map { lines[index].substring(it.start, it.end) to it.role }
+        }
+
+    // --- language detection ---
+
+    @Test
+    fun resolvesCAndCppExtensions() {
+        listOf("c", "h", "cc", "cpp", "cxx", "hpp", "hh", "hxx", "inl", "ipp").forEach { extension ->
+            assertEquals(extension, SyntaxLanguage.CPP, syntaxLanguageForPath(RepositoryPath.of("src/RetryPolicy.$extension")))
+        }
+    }
+
+    @Test
+    fun resolvesUppercaseHeaderExtension() {
+        assertEquals(SyntaxLanguage.CPP, syntaxLanguageForPath(RepositoryPath.of("include/Types.H")))
+    }
+
+    @Test
+    fun keepsCSharpSeparateFromCpp() {
+        assertEquals(SyntaxLanguage.CSHARP, syntaxLanguageForPath(RepositoryPath.of("src/RetryPolicy.cs")))
+    }
+
+    // --- C++ ---
+
+    @Test
+    fun colorsCppKeywords() {
+        val line = tokens(SyntaxLanguage.CPP, "static constexpr int kMax = nullptr;").single()
+        assertEquals(
+            listOf("static", "constexpr", "int", "nullptr").map { it to TokenRole.KEYWORD },
+            line,
+        )
+    }
+
+    @Test
+    fun colorsIncludeDirectiveAndAngleTarget() {
+        val line = tokens(SyntaxLanguage.CPP, "#include <chrono>").single()
+        assertEquals(listOf("#include" to TokenRole.PREPROCESSOR, " <chrono>" to TokenRole.STRING), line)
+    }
+
+    @Test
+    fun colorsIncludeDirectiveAndQuotedTarget() {
+        val line = tokens(SyntaxLanguage.CPP, "#include \"RetryPolicy.h\"").single()
+        assertEquals(listOf("#include" to TokenRole.PREPROCESSOR, "\"RetryPolicy.h\"" to TokenRole.STRING), line)
+    }
+
+    @Test
+    fun colorsIndentedDirectiveAndItsValue() {
+        val line = tokens(SyntaxLanguage.CPP, "  #define MAX_RETRY 8 // limit").single()
+        assertEquals(
+            listOf("  #define" to TokenRole.PREPROCESSOR, "8" to TokenRole.NUMBER, "// limit" to TokenRole.COMMENT),
+            line,
+        )
+    }
+
+    @Test
+    fun doesNotTreatHashInsideCodeAsDirective() {
+        val line = tokens(SyntaxLanguage.CPP, "int x = 1; #pragma once").single()
+        assertTrue(line.none { it.second == TokenRole.PREPROCESSOR })
+    }
+
+    @Test
+    fun colorsCSharpRegionAsPreprocessor() {
+        val line = tokens(SyntaxLanguage.CSHARP, "#region Fields").single()
+        assertEquals("#region" to TokenRole.PREPROCESSOR, line.first())
+    }
+
+    // --- numbers ---
+
+    @Test
+    fun colorsNumbersWithDigitSeparators() {
+        assertEquals(listOf("30_000" to TokenRole.NUMBER), tokens(SyntaxLanguage.CSHARP, "x = 30_000;").single())
+        assertEquals(listOf("1'000'000" to TokenRole.NUMBER), tokens(SyntaxLanguage.CPP, "x = 1'000'000;").single())
+    }
+
+    @Test
+    fun colorsHexAndSuffixedNumbers() {
+        assertEquals(
+            listOf("0xFF" to TokenRole.NUMBER, "2.5f" to TokenRole.NUMBER, "10UL" to TokenRole.NUMBER),
+            tokens(SyntaxLanguage.CPP, "a(0xFF, 2.5f, 10UL);").single(),
+        )
+    }
+
+    // --- multi-line comments ---
+
+    @Test
+    fun colorsEveryLineOfMultiLineBlockComment() {
+        val result = tokens(
+            SyntaxLanguage.CPP,
+            "/*",
+            " * waits before retrying",
+            " */",
+            "int x;",
+        )
+        assertEquals(listOf("/*" to TokenRole.COMMENT), result[0])
+        assertEquals(listOf(" * waits before retrying" to TokenRole.COMMENT), result[1])
+        assertEquals(listOf(" */" to TokenRole.COMMENT), result[2])
+        assertEquals(listOf("int" to TokenRole.KEYWORD), result[3])
+    }
+
+    @Test
+    fun highlightsCodeAfterCommentClosesOnSameLine() {
+        val result = tokens(SyntaxLanguage.CPP, "int a; /* starts", "ends */ return 1;")
+        assertEquals(listOf("int" to TokenRole.KEYWORD, "/* starts" to TokenRole.COMMENT), result[0])
+        assertEquals(
+            listOf("ends */" to TokenRole.COMMENT, "return" to TokenRole.KEYWORD, "1" to TokenRole.NUMBER),
+            result[1],
+        )
+    }
+
+    @Test
+    fun keepsBlankLinesInsideCommentAndStaysOpen() {
+        val result = tokens(SyntaxLanguage.CSHARP, "/* a", "", "b */", "var x;")
+        assertTrue(result[1].isEmpty())
+        assertEquals(listOf("b */" to TokenRole.COMMENT), result[2])
+        assertEquals(listOf("var" to TokenRole.KEYWORD), result[3])
+    }
+
+    @Test
+    fun singleLineBlockCommentDoesNotLeakToNextLine() {
+        val result = tokens(SyntaxLanguage.CPP, "/* done */ int a;", "int b;")
+        assertEquals(listOf("/* done */" to TokenRole.COMMENT, "int" to TokenRole.KEYWORD), result[0])
+        assertEquals(listOf("int" to TokenRole.KEYWORD), result[1])
+    }
+
+    @Test
+    fun slashStarSlashOpensCommentWithoutClosingIt() {
+        val result = tokens(SyntaxLanguage.CPP, "/*/", "still comment */", "int a;")
+        assertEquals(listOf("still comment */" to TokenRole.COMMENT), result[1])
+        assertEquals(listOf("int" to TokenRole.KEYWORD), result[2])
+    }
+
+    @Test
+    fun commentOpenerInsideStringDoesNotOpenComment() {
+        val result = tokens(SyntaxLanguage.CPP, "auto s = \"/* not a comment\";", "int a;")
+        assertEquals(listOf("auto" to TokenRole.KEYWORD, "\"/* not a comment\"" to TokenRole.STRING), result[0])
+        assertEquals(listOf("int" to TokenRole.KEYWORD), result[1])
+    }
+
+    @Test
+    fun commentOpenerInsideLineCommentDoesNotOpenComment() {
+        val result = tokens(SyntaxLanguage.CPP, "// see /* below", "int a;")
+        assertEquals(listOf("// see /* below" to TokenRole.COMMENT), result[0])
+        assertEquals(listOf("int" to TokenRole.KEYWORD), result[1])
+    }
+
+    @Test
+    fun colorsEveryLineOfMultiLineXmlComment() {
+        val result = tokens(SyntaxLanguage.XML, "<!-- first", "second", "third --> <a>")
+        assertEquals(listOf("<!-- first" to TokenRole.COMMENT), result[0])
+        assertEquals(listOf("second" to TokenRole.COMMENT), result[1])
+        assertEquals("third -->" to TokenRole.COMMENT, result[2].first())
+    }
+
+    @Test
+    fun languageWithoutBlockCommentsNeverCarriesState() {
+        val result = tokens(SyntaxLanguage.PYTHON, "x = 1  # /* note", "return x")
+        assertEquals(listOf("return" to TokenRole.KEYWORD), result[1])
+    }
+
+    @Test
+    fun unterminatedCommentColorsRestOfFile() {
+        val result = tokens(SyntaxLanguage.CPP, "/* never closed", "int a;", "int b;")
+        assertEquals(listOf("int a;" to TokenRole.COMMENT), result[1])
+        assertEquals(listOf("int b;" to TokenRole.COMMENT), result[2])
+    }
+}
--- a/docs/development-log.md
+++ b/docs/development-log.md
@ -1269,3 +1269,27 @@ This is the append-only implementation and handoff record shared by Codex and Cl
 - Next recommended task: none queued from this incident.
 - Next owner: Claude, continuing per the standing direction.

+## 2026-09-28 — TASK-049: C/C++ syntax highlighting and multi-line comment coloring
+
+- Request: during the redesign discussion the human product owner said the team mainly reads C# and
+  C++, asked for C++ to be implemented, and asked for TASK-048's known limitation (a multi-line
+  block comment only colored on its first and last line) to be fixed.
+- What changed: `SyntaxHighlighter.kt` gained a `CPP` language (`.c .h .cc .cpp .cxx .hpp .hh .hxx
+  .inl .ipp`), a preprocessor token role and color, a number pattern that accepts hex and digit
+  separators, and `tokenizeLines`/`highlightLines`, which carry "inside a block comment" from line
+  to line for `/* */` and `<!-- -->`. `CodeBlock` now highlights the whole file once inside
+  `remember` instead of re-highlighting each line on every recomposition.
+- Where it was done: the worktree `awesome-pascal-3f2ada` (branch
+  `claude/app-features-purpose-c45235`), fast-forwarded to `39be1b7` with the uncommitted
+  TASK-045..048 changes copied in from the main checkout, because the session's guardrail blocks
+  edits to the main checkout. Nothing is committed yet; the main checkout is untouched.
+- Checks and results: `./gradlew compileDebugKotlin compileDebugUnitTestKotlin testDebugUnitTest
+  assembleDebug lintDebug` BUILD SUCCESSFUL; 289 unit tests, 0 failures (21 new in
+  `SyntaxHighlighterTest`); lint 0 errors, 40 warnings.
+- Live verification: not done -- no device was connected to this session.
+- Known limitations: multi-line strings are still colored only on the line where they start; no
+  type or method coloring yet, so the result is closer to VS Code's defaults than to Visual Studio.
+- Next recommended task: commit TASK-045..048 in the main checkout so this branch can be reconciled
+  with it, then the code-viewer redesign (standalone full-screen viewer, Visual Studio palette,
+  header/source pairing).
+- Next owner: Claude.
--- a/tasks/049-cpp-highlighting-and-multiline-comments.md
+++ b/tasks/049-cpp-highlighting-and-multiline-comments.md
@ -0,0 +1,75 @@
+# TASK-049: C/C++ syntax highlighting and multi-line comment coloring
+
+Status: implemented; see Evidence for check results; device confirmation pending
+Owner: Claude
+Reviewer: human product owner
+
+## Outcome
+
+The human product owner's team mainly reads C# and C++ in this app. C/C++ files currently fall
+back to plain, uncolored text, and a block comment that spans several lines is only colored on its
+first and last line (TASK-048's recorded known limitation). After this task C/C++ sources are
+highlighted, and a multi-line comment keeps its comment color on every line it covers, in every
+language that has block comments.
+
+## Scope
+
+- Included: a `CPP` language (`.c .h .cc .cpp .cxx .hpp .hh .hxx .inl .ipp`) with its keyword set;
+  preprocessor directives (`#include`, `#pragma`, `#define`, C#'s `#region` ...) in their own color,
+  with an `#include <...>` target colored as a string; cross-line block-comment state (`/* */` and
+  `<!-- -->`) carried from one line to the next; numbers with digit separators (`30_000`,
+  `1'000'000`) and hex literals; unit tests for all of the above.
+- Excluded: a real parser. Multi-line *strings* (C++ raw strings, C# verbatim/raw strings, Python
+  triple quotes) still only color on the line where they start. Type/method coloring, the Visual
+  Studio palette, the header/source pairing view and the standalone full-screen viewer belong to
+  the redesign tasks that follow.
+
+## Writable paths
+
+- `app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighter.kt`
+- `app/src/main/java/com/ubisam/ubgitea/feature/codebrowser/CodeBrowserScreen.kt` (`CodeBlock` only)
+- `app/src/test/java/com/ubisam/ubgitea/feature/codebrowser/content/SyntaxHighlighterTest.kt`
+- `tasks/049-cpp-highlighting-and-multiline-comments.md`, `docs/development-log.md`
+
+## Acceptance criteria
+
+- [x] `.c .h .cc .cpp .cxx .hpp .hh .hxx .inl .ipp` files resolve to the C/C++ language.
+- [x] C/C++ keywords, strings, numbers, line comments and block comments are colored.
+- [x] `#include <chrono>` colors the directive as preprocessor and `<chrono>` as a string.
+- [x] Every line inside a multi-line `/* ... */` or `<!-- ... -->` comment is colored as a comment,
+      and code after the closing delimiter on the same line is highlighted normally.
+- [x] A `/*` inside a string literal or after `//` does not open a comment.
+- [x] Highlighting is computed once per file, not on every recomposition.
+- [x] Unit tests cover the criteria above.
+- [ ] Confirmed on the human product owner's device against real C++ sources.
+
+## Security and privacy
+
+No additional concerns. No network, storage or logging is touched.
+
+## Required checks
+
+```text
+./gradlew compileDebugKotlin compileDebugUnitTestKotlin testDebugUnitTest assembleDebug lintDebug
+```
+
+## Evidence
+
+Recorded on 2026-09-28 in the worktree `awesome-pascal-3f2ada`, on top of `39be1b7` plus the
+still-uncommitted TASK-045..048 changes copied from the main checkout, using Android Studio's
+bundled JDK (`D:\AndroidStudio\jbr`, OpenJDK 21):
+
+- `./gradlew compileDebugKotlin compileDebugUnitTestKotlin testDebugUnitTest` -- passed; 289 tests,
+  0 failures, 0 errors, 0 skipped. New `SyntaxHighlighterTest`: 21 tests, all passing.
+- `./gradlew assembleDebug lintDebug` -- passed; lint 0 errors, 40 warnings.
+- `SyntaxHighlighter.kt`: new `CPP` language and extension mapping; `tokenizeLines` (Compose-free,
+  carries open block-comment state across lines); `highlightLines`; preprocessor role and color;
+  number pattern extended to hex and digit separators. `highlightLine` kept as a single-line
+  wrapper.
+- `CodeBrowserScreen.kt`: `CodeBlock` highlights the whole file once inside `remember` and renders
+  the cached lines in both the wrap and no-wrap branches.
+- Not done: installing on a device. No device was connected to this session.
+
+## Review findings
+
+None yet.