perf(icons): share FontFamily + TextMeasurer across Material Symbol icons

Material Symbol icons were allocating a fresh Font wrapper on every
composition (Font(resource = ...) returns a new instance each call),
which invalidated the remember(font) cache in rememberMaterialSymbolsFontFamily
and forced a fresh TextMeasurer per call site. Tint was also baked into
the TextStyle passed to measure(), so any tint change (selected /
unselected reaction icons, hover states) produced a cache miss.

Hoist the FontFamily + TextMeasurer to CompositionLocals provided once
at the root (AmethystTheme on Android, MaterialTheme wrapper on desktop)
via ProvideMaterialSymbols. Every icon in the subtree now reuses:

- One FontFamily (Skia typeface cache hit for every subsequent glyph)
- One TextMeasurer with a 64-entry LRU, shared across all call sites
  so its measurement cache is hit across 300+ MaterialSymbols usages
- Tint applied via drawText(layout, color = tint) instead of TextStyle,
  so the measured TextLayoutResult is reused across tint variations

Icon(symbol = ...) now delegates to Material3's Icon(painter = ...),
restoring proper sizing/semantics without the custom Box+drawBehind
workaround. autoMirror handled inside the painter's onDraw. The
previously-unused MaterialSymbolPainter is now the single render path.

The weight parameter is dropped from the Icon/Painter APIs since the
app uses a single weight globally (MaterialSymbolsDefaults.WEIGHT).

A local fallback path keeps @Preview composables that don't wrap in
the theme renderable (per-composition allocation, same cost as before).

https://claude.ai/code/session_01V9esGUFH72ujCQNWCAnjKN

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/theme/Theme.kt

@@ -61,6 +61,7 @@ import com.halilibo.richtext.ui.resolveDefaults
 import com.patrykandpatrick.vico.compose.common.VicoTheme
 import com.patrykandpatrick.vico.compose.common.VicoTheme.CandlestickCartesianLayerColors
 import com.vitorpamplona.amethyst.Amethyst
+import com.vitorpamplona.amethyst.commons.icons.symbols.ProvideMaterialSymbols
 import com.vitorpamplona.amethyst.model.ThemeType
 
 private val DarkColorPalette =
@@ -591,7 +592,7 @@ fun AmethystTheme(
         colorScheme = colors,
         typography = Typography,
         shapes = Shapes,
-        content = content,
+        content = { ProvideMaterialSymbols(content) },
     )
 
     val view = LocalView.current

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/Icon.kt

@@ -20,29 +20,11 @@
  */
 package com.vitorpamplona.amethyst.commons.icons.symbols
 
-import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.defaultMinSize
 import androidx.compose.material3.LocalContentColor
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.drawBehind
-import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.drawscope.scale
+import androidx.compose.material3.Icon as Material3Icon
-import androidx.compose.ui.graphics.drawscope.translate
-import androidx.compose.ui.platform.LocalDensity
-import androidx.compose.ui.platform.LocalLayoutDirection
-import androidx.compose.ui.semantics.Role
-import androidx.compose.ui.semantics.contentDescription
-import androidx.compose.ui.semantics.role
-import androidx.compose.ui.semantics.semantics
-import androidx.compose.ui.text.TextStyle
-import androidx.compose.ui.text.drawText
-import androidx.compose.ui.text.rememberTextMeasurer
-import androidx.compose.ui.unit.LayoutDirection
-import androidx.compose.ui.unit.dp
-
-private val IconDefaultSize = 24.dp
 
 @Composable
 fun Icon(
@@ -50,49 +32,13 @@ fun Icon(
     contentDescription: String?,
     modifier: Modifier = Modifier,
     tint: Color = LocalContentColor.current,
-    weight: Int = MaterialSymbolsDefaults.WEIGHT,
 ) {
-    val fontFamily = rememberMaterialSymbolsFontFamily(weight)
+    Material3Icon(
-    val textMeasurer = rememberTextMeasurer()
+        painter = rememberMaterialSymbolPainter(symbol, tint),
-    val density = LocalDensity.current
+        contentDescription = contentDescription,
-    val mirror = symbol.autoMirror && LocalLayoutDirection.current == LayoutDirection.Rtl
+        modifier = modifier,
-
+        // Tint is already baked into the painter draw; pass Unspecified so Material3 doesn't
-    val semanticsModifier =
+        // double-tint via a ColorFilter.
-        if (contentDescription != null) {
+        tint = Color.Unspecified,
-            Modifier.semantics {
-                this.contentDescription = contentDescription
-                this.role = Role.Image
-            }
-        } else {
-            Modifier
-        }
-
-    Box(
-        modifier =
-            modifier
-                .defaultMinSize(IconDefaultSize, IconDefaultSize)
-                .drawBehind {
-                    val sizePx = size.minDimension
-                    val fontSize = with(density) { sizePx.toSp() }
-                    val layout =
-                        textMeasurer.measure(
-                            text = symbol.glyph,
-                            style =
-                                TextStyle(
-                                    fontFamily = fontFamily,
-                                    fontSize = fontSize,
-                                    color = tint,
-                                ),
-                        )
-                    val tx = (size.width - layout.size.width) / 2f
-                    val ty = (size.height - layout.size.height) / 2f
-                    if (mirror) {
-                        scale(scaleX = -1f, scaleY = 1f, pivot = Offset(size.width / 2f, size.height / 2f)) {
-                            translate(tx, ty) { drawText(layout) }
-                        }
-                    } else {
-                        translate(tx, ty) { drawText(layout) }
-                    }
-                }.then(semanticsModifier),
     )
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/MaterialSymbolPainter.kt

@@ -23,57 +23,63 @@ package com.vitorpamplona.amethyst.commons.icons.symbols
 import androidx.compose.material3.LocalContentColor
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.drawscope.DrawScope
+import androidx.compose.ui.graphics.drawscope.scale
 import androidx.compose.ui.graphics.drawscope.translate
 import androidx.compose.ui.graphics.painter.Painter
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.text.TextMeasurer
 import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.drawText
 import androidx.compose.ui.text.font.FontFamily
-import androidx.compose.ui.text.rememberTextMeasurer
 import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.LayoutDirection
 
 @Composable
 fun rememberMaterialSymbolPainter(
     symbol: MaterialSymbol,
     tint: Color = LocalContentColor.current,
-    weight: Int = MaterialSymbolsDefaults.WEIGHT,
 ): Painter {
-    val fontFamily = rememberMaterialSymbolsFontFamily(weight)
+    val fontFamily = materialSymbolsFontFamily()
-    val textMeasurer = rememberTextMeasurer()
+    val textMeasurer = materialSymbolsTextMeasurer()
     val density = LocalDensity.current
-    return remember(symbol, fontFamily, tint, density) {
+    val rtl = LocalLayoutDirection.current == LayoutDirection.Rtl
-        MaterialSymbolPainter(symbol, fontFamily, tint, textMeasurer, density)
+    return remember(symbol, fontFamily, textMeasurer, density, tint, rtl) {
+        MaterialSymbolPainter(symbol, fontFamily, textMeasurer, density, tint, rtl)
     }
 }
 
 private class MaterialSymbolPainter(
     private val symbol: MaterialSymbol,
     private val fontFamily: FontFamily,
-    private val tint: Color,
     private val textMeasurer: TextMeasurer,
     private val density: Density,
+    private val tint: Color,
+    private val rtl: Boolean,
 ) : Painter() {
     override val intrinsicSize: Size = Size.Unspecified
 
     override fun DrawScope.onDraw() {
         val sizePx = size.minDimension
         val fontSize = with(density) { sizePx.toSp() }
+        // TextStyle omits color; we override at draw time so TextMeasurer's cache hits across tints.
         val layout =
             textMeasurer.measure(
                 text = symbol.glyph,
-                style =
+                style = TextStyle(fontFamily = fontFamily, fontSize = fontSize),
-                    TextStyle(
-                        fontFamily = fontFamily,
-                        fontSize = fontSize,
-                        color = tint,
-                    ),
             )
         val tx = (size.width - layout.size.width) / 2f
         val ty = (size.height - layout.size.height) / 2f
-        translate(tx, ty) { drawText(layout) }
+        if (symbol.autoMirror && rtl) {
+            scale(scaleX = -1f, scaleY = 1f, pivot = Offset(size.width / 2f, size.height / 2f)) {
+                translate(tx, ty) { drawText(layout, color = tint) }
+            }
+        } else {
+            translate(tx, ty) { drawText(layout, color = tint) }
+        }
     }
 }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/MaterialSymbolsFont.kt

@@ -21,27 +21,79 @@
 package com.vitorpamplona.amethyst.commons.icons.symbols
 
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.ProvidableCompositionLocal
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.staticCompositionLocalOf
+import androidx.compose.ui.text.TextMeasurer
 import androidx.compose.ui.text.font.FontFamily
 import androidx.compose.ui.text.font.FontVariation
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.rememberTextMeasurer
 import com.vitorpamplona.amethyst.commons.resources.Res
 import com.vitorpamplona.amethyst.commons.resources.material_symbols_outlined
 import org.jetbrains.compose.resources.Font
 
+// Held on CompositionLocal so every Material Symbol call site in the tree reuses one FontFamily
+// instance. Without this, every Icon() composition allocates a new Font wrapper, breaks its own
+// remember cache, and forces a fresh TextMeasurer per call site.
+val LocalMaterialSymbolsFontFamily: ProvidableCompositionLocal<FontFamily?> = staticCompositionLocalOf { null }
+
+// Shared TextMeasurer so its internal LRU cache is hit by every icon draw in the tree.
+val LocalMaterialSymbolsTextMeasurer: ProvidableCompositionLocal<TextMeasurer?> = staticCompositionLocalOf { null }
+
+private const val TEXT_MEASURER_CACHE_SIZE = 64
+
+/**
+ * Builds the Material Symbols FontFamily and a shared TextMeasurer once for the subtree and
+ * exposes them via CompositionLocal. Wrap app roots (AmethystTheme, desktop MaterialTheme) in this.
+ */
 @Composable
-fun rememberMaterialSymbolsFontFamily(weight: Int = MaterialSymbolsDefaults.WEIGHT): FontFamily {
+fun ProvideMaterialSymbols(content: @Composable () -> Unit) {
     val font =
         Font(
             resource = Res.font.material_symbols_outlined,
-            weight = FontWeight(weight),
+            weight = FontWeight(MaterialSymbolsDefaults.WEIGHT),
             variationSettings =
                 FontVariation.Settings(
-                    FontVariation.weight(weight),
+                    FontVariation.weight(MaterialSymbolsDefaults.WEIGHT),
                     FontVariation.Setting("FILL", MaterialSymbolsDefaults.FILL),
                     FontVariation.Setting("opsz", MaterialSymbolsDefaults.OPTICAL_SIZE),
                     FontVariation.Setting("GRAD", MaterialSymbolsDefaults.GRADE),
                 ),
         )
-    return remember(font) { FontFamily(font) }
+    // Keyless remember: the Font wrapper identity changes every composition but the underlying
+    // resource is a compile-time constant, so one FontFamily for the lifetime of the subtree.
+    val fontFamily = remember { FontFamily(font) }
+    val textMeasurer = rememberTextMeasurer(cacheSize = TEXT_MEASURER_CACHE_SIZE)
+    CompositionLocalProvider(
+        LocalMaterialSymbolsFontFamily provides fontFamily,
+        LocalMaterialSymbolsTextMeasurer provides textMeasurer,
+        content = content,
+    )
+}
+
+@Composable
+internal fun materialSymbolsFontFamily(): FontFamily = LocalMaterialSymbolsFontFamily.current ?: localMaterialSymbolsFontFamilyFallback()
+
+@Composable
+internal fun materialSymbolsTextMeasurer(): TextMeasurer =
+    LocalMaterialSymbolsTextMeasurer.current
+        ?: rememberTextMeasurer(cacheSize = TEXT_MEASURER_CACHE_SIZE)
+
+@Composable
+private fun localMaterialSymbolsFontFamilyFallback(): FontFamily {
+    val font =
+        Font(
+            resource = Res.font.material_symbols_outlined,
+            weight = FontWeight(MaterialSymbolsDefaults.WEIGHT),
+            variationSettings =
+                FontVariation.Settings(
+                    FontVariation.weight(MaterialSymbolsDefaults.WEIGHT),
+                    FontVariation.Setting("FILL", MaterialSymbolsDefaults.FILL),
+                    FontVariation.Setting("opsz", MaterialSymbolsDefaults.OPTICAL_SIZE),
+                    FontVariation.Setting("GRAD", MaterialSymbolsDefaults.GRADE),
+                ),
+        )
+    return remember { FontFamily(font) }
 }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -71,6 +71,7 @@ import androidx.compose.ui.window.application
 import androidx.compose.ui.window.rememberWindowState
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.commons.icons.symbols.ProvideMaterialSymbols
 import com.vitorpamplona.amethyst.commons.relayClient.nip17Dm.unwrapAndUnsealOrNull
 import com.vitorpamplona.amethyst.desktop.account.AccountManager
 import com.vitorpamplona.amethyst.desktop.account.AccountState
@@ -740,6 +741,7 @@ fun App(
     MaterialTheme(
         colorScheme = darkColorScheme(),
     ) {
+        ProvideMaterialSymbols {
             Surface(
                 modifier = Modifier.fillMaxSize(),
                 color = MaterialTheme.colorScheme.background,
@@ -886,6 +888,7 @@ fun App(
             }
         }
     }
+}
 
 @Composable
 fun MainContent(