Implement skeleton for backup sheets.

core-ui/src/main/java/org/signal/core/ui/Icons.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2024 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.ui
+
+import androidx.compose.material3.Icon
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.drawWithCache
+import androidx.compose.ui.graphics.BlendMode
+import androidx.compose.ui.graphics.Brush
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.CompositingStrategy
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.graphics.painter.Painter
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.tooling.preview.Preview
+
+object Icons {
+  /**
+   * Icon that takes a Brush instead of a Color for its foreground
+   */
+  @Composable
+  fun BrushedForeground(
+    painter: Painter,
+    contentDescription: String?,
+    foregroundBrush: Brush,
+    modifier: Modifier = Modifier
+  ) {
+    Icon(
+      painter = painter,
+      contentDescription = contentDescription,
+      modifier = modifier
+        .graphicsLayer { compositingStrategy = CompositingStrategy.Offscreen }
+        .drawWithCache {
+          onDrawWithContent {
+            drawContent()
+            drawRect(foregroundBrush, blendMode = BlendMode.SrcAtop)
+          }
+        }
+    )
+  }
+}
+
+@Preview
+@Composable
+private fun BrushedForegroundPreview() {
+  Previews.Preview {
+    Icons.BrushedForeground(
+      painter = painterResource(id = android.R.drawable.ic_menu_camera),
+      contentDescription = null,
+      foregroundBrush = Brush.linearGradient(listOf(Color.Red, Color.Blue))
+    )
+  }
+}