perf: replace nested Row/Column with custom NoteComposeLayout

Create a single-pass custom Layout for NoteCompose that replaces
the nested Row > Column > Column structure with direct constraint
calculation using known fixed dimensions (55dp author column, 10dp
gap, 12dp padding).

This eliminates Row's two-pass measurement (measure author first,
then content with remaining width), reduces content Column children
from ~6 to ~3, and pre-computes all pixel dimensions once.

https://claude.ai/code/session_01Fam5VHNaNkKBBafg1gRfFS

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/layouts/NoteComposeLayout.kt

@@ -0,0 +1,207 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.layouts
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.Layout
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.unit.Constraints
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.ui.theme.Size55dp
+
+private val ZeroConstraints = Constraints.fixed(0, 0)
+
+@Immutable
+private data class NoteLayoutPx(
+    val authorWidth: Int,
+    val authorContentGap: Int,
+    val authorBadgeGap: Int,
+    val contentSpacer: Int,
+    val padStart: Int,
+    val padEnd: Int,
+    val padTop: Int,
+)
+
+/**
+ * Custom single-pass layout for note items that replaces nested Row/Column
+ * measurements with direct constraint calculation using known fixed dimensions.
+ *
+ * Layout structure (when [showAuthorColumn] is true):
+ * ```
+ * ┌──────────────────────────────────────────────┐
+ * │ padding (start=12, end=12, top=10)           │
+ * │ ┌──────┐ 10dp ┌────────────────────────────┐ │
+ * │ │author│  gap  │ firstRow                   │ │
+ * │ │ 55dp │       │ secondRow (optional)       │ │
+ * │ │      │       │ 4dp spacer (optional)      │ │
+ * │ ├──────┤ 5dp   │ noteContent                │ │
+ * │ │relay │  gap  │                            │ │
+ * │ │badges│       │                            │ │
+ * │ └──────┘       └────────────────────────────┘ │
+ * ├───────────────────────────────────────────────┤
+ * │ reactionsRow (full width, no side padding)    │
+ * └───────────────────────────────────────────────┘
+ * ```
+ *
+ * Performance benefits over nested Row/Column:
+ * - Eliminates Row's two-pass measurement (measure author, then content with remaining width)
+ * - Uses pre-computed pixel dimensions for author column width (55dp) and gaps
+ * - Reduces content Column children from ~6 to ~3
+ * - Single measure pass positions all sections with known constraints
+ *
+ * @param addPadding Whether to add standard note padding (12dp sides, 10dp top)
+ * @param showAuthorColumn Whether to reserve space for the author picture column
+ * @param showSecondRow Whether to measure and place the second info row
+ * @param showContentSpacer Whether to add a 4dp spacer between header rows and content
+ */
+@Composable
+fun NoteComposeLayout(
+    modifier: Modifier = Modifier,
+    addPadding: Boolean = true,
+    showAuthorColumn: Boolean = true,
+    showSecondRow: Boolean = false,
+    showContentSpacer: Boolean = true,
+    authorPicture: @Composable () -> Unit,
+    relayBadges: @Composable () -> Unit,
+    firstRow: @Composable () -> Unit,
+    secondRow: @Composable () -> Unit,
+    noteContent: @Composable () -> Unit,
+    reactionsRow: @Composable () -> Unit,
+) {
+    val density = LocalDensity.current
+    val px =
+        remember(density) {
+            with(density) {
+                NoteLayoutPx(
+                    authorWidth = Size55dp.roundToPx(),
+                    authorContentGap = 10.dp.roundToPx(),
+                    authorBadgeGap = 5.dp.roundToPx(),
+                    contentSpacer = 4.dp.roundToPx(),
+                    padStart = 12.dp.roundToPx(),
+                    padEnd = 12.dp.roundToPx(),
+                    padTop = 10.dp.roundToPx(),
+                )
+            }
+        }
+
+    Layout(
+        content = {
+            // Slot 0: Author picture (55x55 area)
+            Box { authorPicture() }
+            // Slot 1: Relay badges (55dp wide, below author)
+            Box { relayBadges() }
+            // Slot 2: First row (author name, time, options)
+            Box { firstRow() }
+            // Slot 3: Second row (NIP05, location, PoW)
+            Box { secondRow() }
+            // Slot 4: Note content (event-specific + zap splits + approval)
+            Column(Modifier.fillMaxWidth()) { noteContent() }
+            // Slot 5: Reactions row (full width)
+            Column(Modifier.fillMaxWidth()) { reactionsRow() }
+        },
+        modifier = modifier,
+    ) { measurables, constraints ->
+        val maxWidth = constraints.maxWidth
+
+        // Compute padding offsets
+        val padStart = if (addPadding) px.padStart else 0
+        val padEnd = if (addPadding) px.padEnd else 0
+        val padTop = if (addPadding) px.padTop else 0
+
+        // Compute column widths from known dimensions
+        val innerWidth = maxWidth - padStart - padEnd
+        val authorW = if (showAuthorColumn) px.authorWidth else 0
+        val gap = if (showAuthorColumn) px.authorContentGap else 0
+        val contentWidth = (innerWidth - authorW - gap).coerceAtLeast(0)
+
+        // Build constraints for each section
+        val authorConstraints =
+            if (showAuthorColumn) Constraints(maxWidth = px.authorWidth) else ZeroConstraints
+        val contentConstraints = Constraints(maxWidth = contentWidth)
+
+        // Measure all children in a single pass with pre-computed constraints
+        val authorPlaceable = measurables[0].measure(authorConstraints)
+        val relayPlaceable = measurables[1].measure(authorConstraints)
+        val firstRowPlaceable = measurables[2].measure(contentConstraints)
+        val secondRowPlaceable =
+            measurables[3].measure(
+                if (showSecondRow) contentConstraints else ZeroConstraints,
+            )
+        val contentPlaceable = measurables[4].measure(contentConstraints)
+        val reactionsPlaceable =
+            measurables[5].measure(Constraints(maxWidth = maxWidth))
+
+        // Calculate section heights
+        val spacer = if (showContentSpacer) px.contentSpacer else 0
+
+        val contentColumnHeight =
+            firstRowPlaceable.height +
+                (if (showSecondRow) secondRowPlaceable.height else 0) +
+                spacer +
+                contentPlaceable.height
+
+        val authorColumnHeight =
+            if (showAuthorColumn) {
+                authorPlaceable.height + px.authorBadgeGap + relayPlaceable.height
+            } else {
+                0
+            }
+
+        val mainAreaHeight = maxOf(authorColumnHeight, contentColumnHeight)
+        val totalHeight = padTop + mainAreaHeight + reactionsPlaceable.height
+
+        layout(maxWidth, totalHeight.coerceAtLeast(constraints.minHeight)) {
+            // Place author column (inside padding)
+            if (showAuthorColumn) {
+                authorPlaceable.placeRelative(padStart, padTop)
+                relayPlaceable.placeRelative(
+                    padStart,
+                    padTop + authorPlaceable.height + px.authorBadgeGap,
+                )
+            }
+
+            // Place content column (to the right of author, inside padding)
+            val contentX = padStart + authorW + gap
+            var y = padTop
+
+            firstRowPlaceable.placeRelative(contentX, y)
+            y += firstRowPlaceable.height
+
+            if (showSecondRow) {
+                secondRowPlaceable.placeRelative(contentX, y)
+                y += secondRowPlaceable.height
+            }
+
+            y += spacer
+
+            contentPlaceable.placeRelative(contentX, y)
+
+            // Place reactions row at full width, below main area
+            reactionsPlaceable.placeRelative(0, padTop + mainAreaHeight)
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/NoteCompose.kt

@@ -70,6 +70,7 @@ import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNo
 import com.vitorpamplona.amethyst.ui.components.GenericLoadable
 import com.vitorpamplona.amethyst.ui.components.RobohashFallbackAsyncImage
 import com.vitorpamplona.amethyst.ui.layouts.GenericRepostLayout
+import com.vitorpamplona.amethyst.ui.layouts.NoteComposeLayout
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.navigation.routes.routeEditDraftTo
 import com.vitorpamplona.amethyst.ui.navigation.routes.routeFor
@@ -178,8 +179,6 @@ import com.vitorpamplona.amethyst.ui.theme.HalfDoubleVertSpacer
 import com.vitorpamplona.amethyst.ui.theme.HalfPadding
 import com.vitorpamplona.amethyst.ui.theme.HalfStartPadding
 import com.vitorpamplona.amethyst.ui.theme.Height4dpModifier
-import com.vitorpamplona.amethyst.ui.theme.RowColSpacing10dp
-import com.vitorpamplona.amethyst.ui.theme.RowColSpacing5dp
 import com.vitorpamplona.amethyst.ui.theme.Size10dp
 import com.vitorpamplona.amethyst.ui.theme.Size25dp
 import com.vitorpamplona.amethyst.ui.theme.Size30dp
@@ -189,12 +188,9 @@ import com.vitorpamplona.amethyst.ui.theme.Size55dp
 import com.vitorpamplona.amethyst.ui.theme.StdHorzSpacer
 import com.vitorpamplona.amethyst.ui.theme.UserNameMaxRowHeight
 import com.vitorpamplona.amethyst.ui.theme.UserNameRowHeight
-import com.vitorpamplona.amethyst.ui.theme.WidthAuthorPictureModifier
-import com.vitorpamplona.amethyst.ui.theme.boostedNoteModifier
 import com.vitorpamplona.amethyst.ui.theme.channelNotePictureModifier
 import com.vitorpamplona.amethyst.ui.theme.grayText
 import com.vitorpamplona.amethyst.ui.theme.newItemBackgroundColor
-import com.vitorpamplona.amethyst.ui.theme.normalWithTopMarginNoteModifier
 import com.vitorpamplona.amethyst.ui.theme.placeholderText
 import com.vitorpamplona.amethyst.ui.theme.replyModifier
 import com.vitorpamplona.quartz.experimental.attestations.attestation.AttestationEvent
@@ -632,74 +628,91 @@ fun InnerNoteWithReactions(
 ) {
     val notBoostedNorQuote = !isBoostedNote && !isQuotedNote
     val editState = observeEdits(baseNote = baseNote, accountViewModel = accountViewModel)
+    val isNotRepost = baseNote.event !is RepostEvent && baseNote.event !is GenericRepostEvent
+    val showSecondRow = isNotRepost && notBoostedNorQuote && accountViewModel.settings.isCompleteUIMode()
 
-    Row(
+    NoteComposeLayout(
-        modifier =
+        modifier = Modifier.fillMaxWidth(),
-            if (!isBoostedNote) {
+        addPadding = !isBoostedNote,
-                normalWithTopMarginNoteModifier
+        showAuthorColumn = notBoostedNorQuote,
-            } else {
+        showSecondRow = showSecondRow,
-                boostedNoteModifier
+        showContentSpacer = isNotRepost,
-            },
+        authorPicture = {
-        horizontalArrangement = RowColSpacing10dp,
+            if (notBoostedNorQuote) {
-    ) {
-        if (notBoostedNorQuote) {
-            Column(WidthAuthorPictureModifier, verticalArrangement = RowColSpacing5dp) {
-                // Draws the boosted picture outside the boosted card.
                 Box(modifier = Size55Modifier, contentAlignment = Alignment.BottomEnd) {
                     RenderAuthorImages(baseNote, nav, accountViewModel)
                 }
-
+            }
+        },
+        relayBadges = {
+            if (notBoostedNorQuote) {
                 BadgeBox(baseNote, accountViewModel, nav)
             }
-        }
+        },
-
+        firstRow = {
-        Column(Modifier.fillMaxWidth()) {
+            FirstUserInfoRow(
-            val showSecondRow =
-                baseNote.event !is RepostEvent &&
-                    baseNote.event !is GenericRepostEvent &&
-                    !isBoostedNote &&
-                    !isQuotedNote &&
-                    accountViewModel.settings.isCompleteUIMode()
-            NoteBody(
                 baseNote = baseNote,
                 showAuthorPicture = isQuotedNote,
-                unPackReply = unPackReply,
-                makeItShort = makeItShort,
-                canPreview = canPreview,
-                showSecondRow = showSecondRow,
                 isPinned = isPinned,
-                quotesLeft = quotesLeft,
-                backgroundColor = backgroundColor,
                 editState = editState,
                 accountViewModel = accountViewModel,
                 nav = nav,
                 moreOptions = moreOptions,
             )
-
+        },
-            RenderApprovalIfNeeded(baseNote, accountViewModel, nav)
+        secondRow = {
-        }
+            if (showSecondRow) {
-    }
+                SecondUserInfoRow(
-
+                    baseNote,
-    val isNotRepost = baseNote.event !is RepostEvent && baseNote.event !is GenericRepostEvent && baseNote.event !is DraftWrapEvent
+                    editState,
-
+                    accountViewModel,
-    if (isNotRepost) {
+                    nav,
-        if (makeItShort) {
+                )
-            Spacer(modifier = DoubleVertSpacer)
+            }
-        } else {
+        },
-            ReactionsRow(
+        noteContent = {
+            RenderNoteRow(
                 baseNote = baseNote,
-                showReactionDetail = notBoostedNorQuote,
+                backgroundColor = backgroundColor,
-                addPadding = !isBoostedNote,
+                makeItShort = makeItShort,
+                canPreview = canPreview,
                 editState = editState,
+                quotesLeft = quotesLeft,
+                unPackReply = unPackReply,
                 accountViewModel = accountViewModel,
                 nav = nav,
             )
-        }
+
-    } else {
+            if (!makeItShort) {
-        if (baseNote.event is DraftWrapEvent) {
+                val noteEvent = baseNote.event
-            Spacer(modifier = DoubleVertSpacer)
+                val zapSplits = remember(noteEvent) { noteEvent?.hasZapSplitSetup() ?: false }
-        }
+                if (zapSplits && noteEvent != null) {
-    }
+                    Spacer(modifier = HalfDoubleVertSpacer)
+                    DisplayZapSplits(noteEvent, false, accountViewModel, nav)
+                }
+            }
+
+            RenderApprovalIfNeeded(baseNote, accountViewModel, nav)
+        },
+        reactionsRow = {
+            if (isNotRepost && baseNote.event !is DraftWrapEvent) {
+                if (makeItShort) {
+                    Spacer(modifier = DoubleVertSpacer)
+                } else {
+                    ReactionsRow(
+                        baseNote = baseNote,
+                        showReactionDetail = notBoostedNorQuote,
+                        addPadding = !isBoostedNote,
+                        editState = editState,
+                        accountViewModel = accountViewModel,
+                        nav = nav,
+                    )
+                }
+            } else if (baseNote.event is DraftWrapEvent) {
+                Spacer(modifier = DoubleVertSpacer)
+            }
+        },
+    )
 }
 
 @Composable