Adaptive welcome screen with compact, medium, and large layouts.

core/ui/src/main/java/org/signal/core/ui/WindowSizeClassExtensions.kt

@@ -6,6 +6,10 @@
 package org.signal.core.ui
 
 import android.content.res.Resources
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalResources
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import androidx.window.core.layout.WindowSizeClass
@@ -31,6 +35,16 @@ fun Resources.getWindowSizeClass(): WindowSizeClass {
   )
 }
 
+@Composable
+fun rememberWindowBreakpoint(): WindowBreakpoint {
+  val resources = LocalResources.current
+  val configuration = LocalConfiguration.current
+
+  return remember(resources, configuration) {
+    resources.getWindowBreakpoint()
+  }
+}
+
 /**
  * Determines the device's form factor (PHONE, FOLDABLE, or TABLET) based on the current
  * [Resources] and window size class.
@@ -39,7 +53,7 @@ fun Resources.getWindowSizeClass(): WindowSizeClass {
  * - Returns [WindowBreakpoint.SMALL] if the width or height is compact.
  * - Returns [WindowBreakpoint.LARGE] if the height is at least the expanded lower bound.
  * - Returns [WindowBreakpoint.MEDIUM] if the width is at least the medium lower bound.
- * - Otherwise, falls back to aspect ratio heuristics: wider (≥ 1.6) is [WindowBreakpoint.LARGE], else [WindowBreakpoint.MEDIUM].
+ * - Otherwise, falls back to aspect ratio heuristics: wider (≥ 1.5) is [WindowBreakpoint.LARGE], else [WindowBreakpoint.MEDIUM].
  *
  * @return the inferred [WindowBreakpoint] for the current device.
  */
@@ -58,7 +72,7 @@ fun Resources.getWindowBreakpoint(): WindowBreakpoint {
   val denominator = minOf(displayMetrics.widthPixels, displayMetrics.heightPixels)
   val aspectRatio = numerator.toFloat() / denominator
 
-  return if (aspectRatio >= 1.6f) {
+  return if (aspectRatio >= 1.5f) {
     WindowBreakpoint.LARGE
   } else {
     WindowBreakpoint.MEDIUM

core/ui/src/main/java/org/signal/core/ui/compose/Layouts.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2026 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.ui.compose
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.layout.SubcomposeLayout
+import androidx.compose.ui.tooling.preview.Preview
+
+/**
+ * Lays out [primary] and [secondary] side by side in a row. [primaryProportion] controls what
+ * fraction of the total width [primary] receives (e.g. 0.5f = equal split).
+ */
+@Composable
+fun SideBySideLayout(
+  primary: @Composable () -> Unit,
+  secondary: @Composable () -> Unit,
+  modifier: Modifier = Modifier,
+  primaryProportion: Float = 0.5f
+) {
+  SubcomposeLayout(modifier = modifier) { constraints ->
+    val primaryWidth = (constraints.maxWidth * primaryProportion).toInt()
+    val secondaryWidth = constraints.maxWidth - primaryWidth
+
+    val primaryPlaceables = subcompose("primary", primary).map { m ->
+      m.measure(constraints.copy(minWidth = primaryWidth, maxWidth = primaryWidth, minHeight = 0))
+    }
+    val primaryHeight = primaryPlaceables.maxOfOrNull { it.height } ?: 0
+
+    val secondaryMeasurables = subcompose("secondary", secondary)
+    val secondaryMinHeight = secondaryMeasurables.maxOfOrNull { it.minIntrinsicHeight(secondaryWidth) } ?: 0
+    val layoutHeight = maxOf(primaryHeight, secondaryMinHeight)
+
+    val secondaryPlaceables = secondaryMeasurables.map { m ->
+      m.measure(constraints.copy(minWidth = secondaryWidth, maxWidth = secondaryWidth, minHeight = layoutHeight, maxHeight = layoutHeight))
+    }
+
+    layout(constraints.maxWidth, layoutHeight) {
+      primaryPlaceables.forEach { it.placeRelative(0, 0) }
+      secondaryPlaceables.forEach { it.placeRelative(primaryWidth, 0) }
+    }
+  }
+}
+
+@Preview
+@Composable
+private fun SideBySideLayoutPreview() {
+  Previews.Preview {
+    SideBySideLayout(
+      primary = {
+        Box(
+          modifier = Modifier
+            .fillMaxSize()
+            .background(color = Color.Red)
+        )
+      },
+      secondary = {
+        Box(
+          modifier = Modifier
+            .fillMaxSize()
+            .background(color = Color.Blue)
+        )
+      },
+      modifier = Modifier.fillMaxSize()
+    )
+  }
+}

core/ui/src/main/java/org/signal/core/ui/compose/SignalPreviews.kt

@@ -100,10 +100,10 @@ annotation class TabletLandscapeDayPreview
 @TabletLandscapeDayPreview
 annotation class TabletDayPreviews
 
-@Preview(name = "tablet portrait (night)", uiMode = Configuration.UI_MODE_NIGHT_YES, device = "spec:width=1280dp,height=840dp,orientation=portrait")
+@Preview(name = "tablet portrait (night)", uiMode = Configuration.UI_MODE_NIGHT_YES, device = "spec:width=840dp,height=1280dp,orientation=portrait")
 annotation class TabletPortraitNightPreview
 
-@Preview(name = "tablet landscape (night)", uiMode = Configuration.UI_MODE_NIGHT_YES, device = "spec:width=840dp,height=1280dp,orientation=landscape")
+@Preview(name = "tablet landscape (night)", uiMode = Configuration.UI_MODE_NIGHT_YES, device = "spec:width=1280dp,height=840dp,orientation=landscape")
 annotation class TabletLandscapeNightPreview
 
 @TabletPortraitNightPreview