RoomListFilters: try to improve ui with animation and fading edges

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2024 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.modifiers
+
+import androidx.compose.animation.animateColorAsState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.drawWithContent
+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
+
+@Composable
+fun horizontalFadingEdgesBrush(
+    showLeft: Boolean,
+    showRight: Boolean,
+    percent: Float = 0.1f,
+): Brush {
+    val leftColor by animateColorAsState(
+        targetValue = if (showLeft) Color.Transparent else Color.White,
+        label = "AnimateLeftColor",
+    )
+    val rightColor by animateColorAsState(
+        targetValue = if (showRight) Color.Transparent else Color.White,
+        label = "AnimateRightColor",
+    )
+    return Brush.horizontalGradient(
+        0f to leftColor,
+        percent to Color.White,
+        1f - percent to Color.White,
+        1f to rightColor
+    )
+}
+
+fun Modifier.fadingEdge(brush: Brush) = this
+    .graphicsLayer(compositingStrategy = CompositingStrategy.Offscreen)
+    .drawWithContent {
+        drawContent()
+        drawRect(brush = brush, blendMode = BlendMode.DstIn)
+    }