perf(markdown): coalesce long plain bullet runs (#1415)

app/src/main/java/com/m57/hermescontrol/ui/chat/MarkdownText.kt

@@ -34,6 +34,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.LinkAnnotation
@@ -43,6 +44,7 @@ import androidx.compose.ui.text.buildAnnotatedString
 import androidx.compose.ui.text.font.FontFamily
 import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.rememberTextMeasurer
 import androidx.compose.ui.text.style.BaselineShift
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextDecoration
@@ -61,6 +63,7 @@ import com.m57.hermescontrol.data.remote.GatewayFileClient
 import com.m57.hermescontrol.theme.LocalHermesStatusColors
 import com.m57.hermescontrol.theme.SearchHighlightColors
 import com.m57.hermescontrol.theme.searchHighlightColors
+import com.m57.hermescontrol.ui.chat.markdown.BulletRun
 import com.m57.hermescontrol.ui.chat.markdown.FnNote
 import com.m57.hermescontrol.ui.chat.markdown.InlineMathSegment
 import com.m57.hermescontrol.ui.chat.markdown.MarkdownInlineStyler
@@ -69,6 +72,8 @@ import com.m57.hermescontrol.ui.chat.markdown.MarkdownMediaResolver
 import com.m57.hermescontrol.ui.chat.markdown.MarkdownTable
 import com.m57.hermescontrol.ui.chat.markdown.MdBlock
 import com.m57.hermescontrol.ui.chat.markdown.TableAlign
+import com.m57.hermescontrol.ui.chat.markdown.buildBulletRunText
+import com.m57.hermescontrol.ui.chat.markdown.coalesceBulletRuns
 import com.m57.hermescontrol.ui.chat.markdown.parseBlocks
 import com.m57.hermescontrol.ui.chat.markdown.splitInlineMath
 import com.m57.hermescontrol.util.BidiUtils
@@ -100,7 +105,7 @@ fun MarkdownText(
     val statusColors = LocalHermesStatusColors.current
     val highlights = searchHighlightColors(statusColors)
     val linkColor = MaterialTheme.colorScheme.primary
-    val blocks = remember(text, isStreaming) { parseBlocks(text) }
+    val blocks = remember(text, isStreaming) { coalesceBulletRuns(parseBlocks(text)) }
     val latexMeasurer = rememberLatexMeasurer()
 
     Column(modifier = modifier.fillMaxWidth()) {
@@ -151,6 +156,7 @@ fun MarkdownText(
                     CompositionLocalProvider(LocalLayoutDirection provides blockDirection) {
                         MarkdownInlineText(
                             text = block.text,
+                            isRtlOverride = isRtl,
                             textColor = textColor,
                             latexMeasurer = latexMeasurer,
                             style =
@@ -167,6 +173,47 @@ fun MarkdownText(
                     }
                 }
 
+                is BulletRun -> {
+                    val density = LocalDensity.current
+                    val bodyStyle = MaterialTheme.typography.bodyMedium.copy(textDirection = TextDirection.Ltr)
+                    val textMeasurer = rememberTextMeasurer()
+                    val runText =
+                        remember(
+                            block,
+                            density,
+                            bodyStyle,
+                            textColor,
+                            searchQuery,
+                            isCurrentMatch,
+                            linkColor,
+                            highlights,
+                        ) {
+                            buildBulletRunText(
+                                run = block,
+                                density = density,
+                                textColor = textColor,
+                                searchQuery = searchQuery,
+                                isCurrentMatch = isCurrentMatch,
+                                linkColor = linkColor,
+                                highlights = highlights,
+                                prefixWidth = { prefix ->
+                                    with(density) {
+                                        textMeasurer
+                                            .measure(prefix, bodyStyle)
+                                            .size.width
+                                            .toSp()
+                                    }
+                                },
+                            )
+                        }
+                    Text(
+                        text = runText,
+                        color = textColor,
+                        style = bodyStyle,
+                        modifier = Modifier.fillMaxWidth().padding(vertical = 1.dp),
+                    )
+                }
+
                 is MdBlock.Bullet -> {
                     val indent = (block.level * 16).dp
                     val isRtl = remember(block.text) { BidiUtils.isRtlText(block.text) }
@@ -195,6 +242,7 @@ fun MarkdownText(
                             Column(modifier = Modifier.weight(1f)) {
                                 MarkdownInlineText(
                                     text = block.text,
+                                    isRtlOverride = isRtl,
                                     textColor = textColor,
                                     latexMeasurer = latexMeasurer,
                                     style =
@@ -254,6 +302,7 @@ fun MarkdownText(
                             Column(modifier = Modifier.weight(1f)) {
                                 MarkdownInlineText(
                                     text = block.text,
+                                    isRtlOverride = isRtl,
                                     textColor = textColor,
                                     latexMeasurer = latexMeasurer,
                                     style =
@@ -301,6 +350,7 @@ fun MarkdownText(
                             Column(modifier = Modifier.weight(1f)) {
                                 MarkdownInlineText(
                                     text = block.text,
+                                    isRtlOverride = isRtl,
                                     textColor = textColor,
                                     latexMeasurer = latexMeasurer,
                                     style =
@@ -347,6 +397,7 @@ fun MarkdownText(
                             if (nestedBlocks.size == 1 && nestedBlocks.single() is MdBlock.Paragraph) {
                                 MarkdownInlineText(
                                     text = block.text,
+                                    isRtlOverride = isRtl,
                                     textColor = textColor,
                                     latexMeasurer = latexMeasurer,
                                     style =
@@ -502,6 +553,7 @@ fun MarkdownText(
                                     )
                                     MarkdownInlineText(
                                         text = note.text,
+                                        isRtlOverride = isRtl,
                                         textColor = textColor,
                                         latexMeasurer = latexMeasurer,
                                         style =
@@ -526,6 +578,7 @@ fun MarkdownText(
                     CompositionLocalProvider(LocalLayoutDirection provides blockDirection) {
                         MarkdownInlineText(
                             text = block.text,
+                            isRtlOverride = isRtl,
                             textColor = textColor,
                             latexMeasurer = latexMeasurer,
                             style =

app/src/main/java/com/m57/hermescontrol/ui/chat/markdown/MarkdownBulletRun.kt

@@ -0,0 +1,121 @@
+package com.m57.hermescontrol.ui.chat.markdown
+
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.ParagraphStyle
+import androidx.compose.ui.text.buildAnnotatedString
+import androidx.compose.ui.text.style.TextIndent
+import androidx.compose.ui.text.withStyle
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.TextUnit
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.m57.hermescontrol.theme.SearchHighlightColors
+import com.m57.hermescontrol.util.BidiUtils
+
+/**
+ * Render-time optimization, not parsed Markdown: a long run of plain bullets drawn as one text node.
+ * Produced only by [coalesceBulletRuns]; kept out of the parser's AST file on purpose.
+ */
+data class BulletRun(
+    val items: List<MdBlock.Bullet>,
+) : MdBlock
+
+/** Runs shorter than this keep the per-row renderer; the win only matters for very long lists. */
+internal const val MIN_BULLET_RUN = 16
+
+/**
+ * A bullet is eligible for coalescing when it is a plain, LTR, single-line item: no nested content
+ * and no inline math (math needs per-item inline content that a merged paragraph run can't host).
+ */
+private fun MdBlock.Bullet.isPlain(): Boolean =
+    nestedSource.isEmpty() &&
+        !BidiUtils.isRtlText(text) &&
+        splitInlineMath(text).none { it is InlineMathSegment.Math }
+
+/**
+ * Replaces each run of at least [minRun] consecutive plain bullets with a single [MdBlock.BulletRun].
+ * Everything else is passed through untouched, so complex lists keep the existing renderer.
+ */
+internal fun coalesceBulletRuns(
+    blocks: List<MdBlock>,
+    minRun: Int = MIN_BULLET_RUN,
+): List<MdBlock> {
+    if (blocks.size < minRun) return blocks
+    val out = ArrayList<MdBlock>(blocks.size)
+    var i = 0
+    while (i < blocks.size) {
+        val block = blocks[i]
+        if (block is MdBlock.Bullet && block.isPlain()) {
+            var end = i + 1
+            while (end < blocks.size) {
+                val next = blocks[end]
+                if (next is MdBlock.Bullet && next.isPlain()) end++ else break
+            }
+            if (end - i >= minRun) {
+                out.add(BulletRun(blocks.subList(i, end).map { it as MdBlock.Bullet }))
+            } else {
+                out.addAll(blocks.subList(i, end))
+            }
+            i = end
+        } else {
+            out.add(block)
+            i++
+        }
+    }
+    return out
+}
+
+private const val BULLET_LEVEL_INDENT_DP = 16
+
+/** The two non-breaking spaces that separate the glyph from the body. */
+internal const val BULLET_PREFIX_PAD = "\u00A0\u00A0"
+
+internal fun bulletGlyph(level: Int): String =
+    when (level % 3) {
+        0 -> "\u2022"
+        1 -> "\u25E6"
+        else -> "\u25AA"
+    }
+
+/**
+ * Builds the merged text for a [BulletRun].
+ *
+ * The list-level offset is dp-based (like the per-row renderer's `padding(start = (level * 16).dp)`).
+ * The hanging indent for wrapped lines also includes the rendered bullet prefix, whose width scales with
+ * the font; [prefixWidth] measures a prefix in the body text style so wrapped lines line up with the body
+ * at any font scale.
+ */
+internal fun buildBulletRunText(
+    run: BulletRun,
+    density: Density,
+    textColor: Color,
+    searchQuery: String,
+    isCurrentMatch: Boolean,
+    linkColor: Color,
+    highlights: SearchHighlightColors,
+    prefixWidth: (String) -> TextUnit,
+): AnnotatedString =
+    buildAnnotatedString {
+        run.items.forEachIndexed { index, item ->
+            val start = with(density) { (item.level * BULLET_LEVEL_INDENT_DP).dp.toSp() }
+            val prefix = bulletGlyph(item.level) + BULLET_PREFIX_PAD
+            val rest = (start.value + prefixWidth(prefix).value).sp
+            withStyle(ParagraphStyle(textIndent = TextIndent(firstLine = start, restLine = rest))) {
+                append(prefix)
+                append(
+                    MarkdownInlineStyler.parseInlineSource(
+                        text = item.text,
+                        textColor = textColor,
+                        searchQuery = searchQuery,
+                        isCurrentMatch = isCurrentMatch,
+                        linkColor = linkColor,
+                        highlights = highlights,
+                        isRtl = false,
+                    ),
+                )
+                // ParagraphStyle breaks lines visually but adds no character; the newline keeps copy/select faithful.
+                if (index < run.items.lastIndex) append('\n')
+            }
+        }
+    }

app/src/main/java/com/m57/hermescontrol/ui/chat/markdown/MarkdownInlineText.kt

@@ -30,8 +30,9 @@ fun MarkdownInlineText(
     linkColor: Color,
     highlights: SearchHighlightColors,
     modifier: Modifier = Modifier,
+    isRtlOverride: Boolean? = null,
 ) {
-    val isRtl = remember(text) { BidiUtils.isRtlText(text) }
+    val isRtl = isRtlOverride ?: remember(text) { BidiUtils.isRtlText(text) }
     val direction = if (isRtl) LayoutDirection.Rtl else LocalLayoutDirection.current
     val resolvedStyle =
         style.copy(