Centralize gradient color definitions

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/colors/Gradient.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.designsystem.colors
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.ReadOnlyComposable
+import androidx.compose.ui.graphics.Color
+import io.element.android.compound.theme.ElementTheme
+
+@Composable
+@ReadOnlyComposable
+fun gradientActionColors(): List<Color> = listOf(
+    ElementTheme.colors.gradientActionStop1,
+    ElementTheme.colors.gradientActionStop2,
+    ElementTheme.colors.gradientActionStop3,
+    ElementTheme.colors.gradientActionStop4,
+)
+
+@Composable
+@ReadOnlyComposable
+fun gradientSubtleColors(): List<Color> = listOf(
+    ElementTheme.colors.gradientSubtleStop1,
+    ElementTheme.colors.gradientSubtleStop2,
+    ElementTheme.colors.gradientSubtleStop3,
+    ElementTheme.colors.gradientSubtleStop4,
+    ElementTheme.colors.gradientSubtleStop5,
+    ElementTheme.colors.gradientSubtleStop6,
+)
+
+@Composable
+@ReadOnlyComposable
+fun gradientInfoColors(): List<Color> = listOf(
+    ElementTheme.colors.gradientInfoStop1,
+    ElementTheme.colors.gradientInfoStop2,
+    ElementTheme.colors.gradientInfoStop3,
+    ElementTheme.colors.gradientInfoStop4,
+    ElementTheme.colors.gradientInfoStop5,
+    ElementTheme.colors.gradientInfoStop6,
+)

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/components/button/SuperButton.kt

@@ -37,6 +37,7 @@ import androidx.compose.ui.graphics.Shape
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.unit.dp
 import io.element.android.compound.theme.ElementTheme
+import io.element.android.libraries.designsystem.colors.gradientActionColors
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.LocalBuildMeta
@@ -68,12 +69,7 @@ fun SuperButton(
             ElementTheme.colors.textActionAccent,
         )
     } else {
-        listOf(
-            ElementTheme.colors.gradientActionStop1,
-            ElementTheme.colors.gradientActionStop2,
-            ElementTheme.colors.gradientActionStop3,
-            ElementTheme.colors.gradientActionStop4,
-        )
+        gradientActionColors()
     }
 
     val shaderBrush = remember(colors) {

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/modifiers/Gradient.kt

@@ -18,6 +18,7 @@ import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.unit.dp
 import io.element.android.compound.theme.ElementTheme
+import io.element.android.libraries.designsystem.colors.gradientSubtleColors
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.LocalBuildMeta
@@ -51,12 +52,10 @@ fun subtleColorStops(
             add(0.75f to ElementTheme.colors.bgCanvasDefault)
             add(1f to Color.Transparent)
         } else {
-            add(0f to ElementTheme.colors.gradientSubtleStop1)
-            add(1 / 5f to ElementTheme.colors.gradientSubtleStop2)
-            add(2 / 5f to ElementTheme.colors.gradientSubtleStop3)
-            add(3 / 5f to ElementTheme.colors.gradientSubtleStop4)
-            add(4 / 5f to ElementTheme.colors.gradientSubtleStop5)
-            add(1f to ElementTheme.colors.gradientSubtleStop6)
+            val colors = gradientSubtleColors()
+            colors.forEachIndexed { index, color ->
+                add(index.toFloat() / (colors.size - 1) to color)
+            }
         }
     }.toTypedArray()
 }

libraries/textcomposer/impl/src/main/kotlin/io/element/android/libraries/textcomposer/components/SendButton.kt

@@ -23,6 +23,7 @@ import androidx.compose.ui.graphics.ShaderBrush
 import androidx.compose.ui.unit.dp
 import io.element.android.compound.theme.ElementTheme
 import io.element.android.compound.tokens.generated.CompoundIcons
+import io.element.android.libraries.designsystem.colors.gradientActionColors
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.components.Icon
@@ -89,12 +90,7 @@ private fun Modifier.buttonBackgroundModifier(
     canSendMessage: Boolean,
 ) = then(
     if (canSendMessage) {
-        val colors = listOf(
-            ElementTheme.colors.gradientActionStop1,
-            ElementTheme.colors.gradientActionStop2,
-            ElementTheme.colors.gradientActionStop3,
-            ElementTheme.colors.gradientActionStop4,
-        )
+        val colors = gradientActionColors()
         Modifier.drawWithCache {
             val verticalGradientBrush = ShaderBrush(
                 LinearGradientShader(