Apply colors to default user avatar in the timeline.

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemEventRow.kt

@@ -346,7 +346,7 @@ private fun MessageSenderInformation(
         }
         // Content
         Row {
-            Avatar(senderAvatar)
+            Avatar(senderAvatar, avatarColors = avatarColors)
             Spacer(modifier = Modifier.width(4.dp))
             Text(
                 text = sender,

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/components/avatar/Avatar.kt

@@ -33,6 +33,7 @@ import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import coil.compose.AsyncImage
+import io.element.android.libraries.designsystem.colors.AvatarColors
 import io.element.android.libraries.designsystem.preview.ElementThemedPreview
 import io.element.android.libraries.designsystem.preview.PreviewGroup
 import io.element.android.libraries.designsystem.preview.debugPlaceholderAvatar
@@ -45,6 +46,7 @@ import timber.log.Timber
 fun Avatar(
     avatarData: AvatarData,
     modifier: Modifier = Modifier,
+    avatarColors: AvatarColors? = null,
     contentDescription: String? = null,
 ) {
     val commonModifier = modifier
@@ -53,6 +55,7 @@ fun Avatar(
     if (avatarData.url.isNullOrBlank()) {
         InitialsAvatar(
             avatarData = avatarData,
+            avatarColors = avatarColors,
             modifier = commonModifier,
         )
     } else {
@@ -85,12 +88,13 @@ private fun ImageAvatar(
 @Composable
 private fun InitialsAvatar(
     avatarData: AvatarData,
+    avatarColors: AvatarColors?,
     modifier: Modifier = Modifier,
 ) {
     // Use temporary color for default avatar background
     val avatarColor = ElementTheme.colors.bgActionPrimaryDisabled
     Box(
-        modifier.background(color = avatarColor),
+        modifier.background(color = avatarColors?.background ?: avatarColor)
     ) {
         val fontSize = avatarData.size.dp.toSp() / 2
         val originalFont = ElementTheme.typography.fontBodyMdRegular
@@ -100,7 +104,7 @@ private fun InitialsAvatar(
             modifier = Modifier.align(Alignment.Center),
             text = avatarData.initial,
             style = originalFont.copy(fontSize = fontSize, lineHeight = lineHeight, letterSpacing = 0.sp),
-            color = Color.White,
+            color = avatarColors?.foreground ?: Color.White,
         )
     }
 }

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/components/avatar/UserAvatarPreview.kt

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.designsystem.components.avatar
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.padding
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import io.element.android.libraries.designsystem.colors.AvatarColors
+import io.element.android.libraries.designsystem.preview.DayNightPreviews
+import io.element.android.libraries.designsystem.preview.ElementPreview
+import io.element.android.libraries.designsystem.theme.components.Text
+import io.element.android.libraries.theme.colors.avatarColorsLight
+
+@DayNightPreviews
+@Composable
+internal fun UserAvatarPreview() = ElementPreview {
+    Column(
+        modifier = Modifier.padding(8.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        repeat(avatarColorsLight.size) {
+            Row(
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                verticalAlignment = Alignment.CenterVertically,
+            ) {
+                // Note: it's OK, since the hash of "0" is 0, the hash of "1" is 1, etc.
+                Avatar(anAvatarData(), avatarColors = AvatarColors("$it"))
+                Text(text = "Color index $it")
+            }
+        }
+    }
+}

libraries/designsystem/src/test/kotlin/io/element/android/libraries/designsystem/colors/AvatarColorsTest.kt

@@ -37,4 +37,16 @@ class AvatarColorsTest {
         assertThat("@bob:domain.org".toHash()).isEqualTo(3)
         assertThat("@charlie:domain.org".toHash()).isEqualTo(0)
     }
+
+    @Test
+    fun `compute string hash reverse`() {
+        assertThat("0".toHash()).isEqualTo(0)
+        assertThat("1".toHash()).isEqualTo(1)
+        assertThat("2".toHash()).isEqualTo(2)
+        assertThat("3".toHash()).isEqualTo(3)
+        assertThat("4".toHash()).isEqualTo(4)
+        assertThat("5".toHash()).isEqualTo(5)
+        assertThat("6".toHash()).isEqualTo(6)
+        assertThat("7".toHash()).isEqualTo(7)
+    }
 }