Add mesh gradient usecases

Jetchat/app/src/main/java/com/example/compose/jetchat/components/MeshUtils.kt

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+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * 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
+ *
+ *     https://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 com.example.compose.jetchat.components
+
+import androidx.compose.animation.core.LinearEasing
+import androidx.compose.animation.core.RepeatMode
+import androidx.compose.animation.core.animateFloat
+import androidx.compose.animation.core.infiniteRepeatable
+import androidx.compose.animation.core.rememberInfiniteTransition
+import androidx.compose.animation.core.tween
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.MeshGradientPainter
+import kotlin.math.PI
+import kotlin.math.cos
+import kotlin.math.sin
+
+/**
+ * A gently animated mesh gradient used as the glow behind the chat [UserInput] bar.
+ *
+ * The softness comes entirely from the mesh:
+ *  - [MeshGradientPainter.hasBicubicColor] gives smooth (non-linear) colour blending, and
+ *  - the outer ring of vertices is fully transparent (alpha 0x00), so the glow feathers to
+ *    nothing at its edges.
+ *
+ * That means no `.blur()` and no linear gradient are needed to reproduce the effect.
+ */
+@Composable
+fun rememberUserInputGlowMeshGradientPainter(): MeshGradientPainter {
+    val transition = rememberInfiniteTransition(label = "userInputGlowMesh")
+    val phase1 by transition.animateFloat(
+        initialValue = 0f,
+        targetValue = (2 * PI).toFloat(),
+        animationSpec = infiniteRepeatable(
+            animation = tween(durationMillis = 2800, easing = LinearEasing),
+            repeatMode = RepeatMode.Restart,
+        ),
+        label = "glowPhase1",
+    )
+    val phase2 by transition.animateFloat(
+        initialValue = 0f,
+        targetValue = (2 * PI).toFloat(),
+        animationSpec = infiniteRepeatable(
+            animation = tween(durationMillis = 4200, easing = LinearEasing),
+            repeatMode = RepeatMode.Restart,
+        ),
+        label = "glowPhase2",
+    )
+
+    // Helper for smooth organic orbital displacement per interior vertex.
+    fun orbit(colIdx: Int, rowIdx: Int, ampX: Float, ampY: Float): Offset {
+        val angle1 = phase1 + colIdx * 0.85f + rowIdx * 0.65f
+        val angle2 = phase2 - colIdx * 0.55f + rowIdx * 0.90f
+        val dx = ampX * (0.72f * cos(angle1) + 0.28f * sin(angle2))
+        val dy = ampY * (0.72f * sin(angle1) + 0.28f * cos(angle2))
+        return Offset(dx, dy)
+    }
+
+    return remember(phase1, phase2) {
+        val uCols = floatArrayOf(0.00f, 0.12f, 0.27f, 0.56f, 0.78f, 1.00f)
+        val vRows = floatArrayOf(0.00f, 0.20f, 0.33f, 0.43f, 0.64f, 0.85f, 1.00f)
+
+        val gridColors = arrayOf(
+            // Row 0: transparent royal-blue boundary (top of the glow).
+            arrayOf(
+                Color(0x000B57D0),
+                Color(0x000B57D0),
+                Color(0x000B57D0),
+                Color(0x000B57D0),
+                Color(0x000B57D0),
+                Color(0x000B57D0),
+            ),
+            // Row 1: high royal-blue aura.
+            arrayOf(
+                Color(0x00125CCF),
+                Color(0x3C1F62D8),
+                Color(0x5C2365D7),
+                Color(0x66125CCF),
+                Color(0x451D63D1),
+                Color(0x001D63D1),
+            ),
+            // Row 2: mid-upper sky-cerulean aura.
+            arrayOf(
+                Color(0x006B88EE),
+                Color(0x80829CF2),
+                Color(0xA86E8DF0),
+                Color(0xB46488EE),
+                Color(0x825C86EC),
+                Color(0x005C86EC),
+            ),
+            // Row 3: lavender left, periwinkle centre, cobalt right shoulder.
+            arrayOf(
+                Color(0x00B6ABFB),
+                Color(0xEEB6ABFB),
+                Color(0xF4A39BFC),
+                Color(0xF59D98FC),
+                Color(0xF25C7CF5),
+                Color(0x18728CF5),
+            ),
+            // Row 4: vibrant orchid-lavender left, electric cobalt right (card height).
+            arrayOf(
+                Color(0x00C2A7FF),
+                Color(0xFFC2A7FF),
+                Color(0xFFC1A6FF),
+                Color(0xFF687DF9),
+                Color(0xF04E6EFA),
+                Color(0x205875FA),
+            ),
+            // Row 5: crisp indigo-cobalt shadow along the bottom.
+            arrayOf(
+                Color(0x007E8AF4),
+                Color(0xE27E8AF4),
+                Color(0xF45A6DFB),
+                Color(0xF6556AFC),
+                Color(0xFA3C5CFC),
+                Color(0x204D6AFB),
+            ),
+            // Row 6: transparent cobalt boundary (bottom of the glow).
+            arrayOf(
+                Color(0x005A6DFB),
+                Color(0x005A6DFB),
+                Color(0x005A6DFB),
+                Color(0x00556AFC),
+                Color(0x003C5CFC),
+                Color(0x003C5CFC),
+            ),
+        )
+
+        MeshGradientPainter(
+            rows = 6,
+            columns = 5,
+            hasBicubicColor = true,
+        ) {
+            for (r in 0..6) {
+                for (c in 0..5) {
+                    val baseU = uCols[c]
+                    val baseV = vRows[r]
+                    val offset = if (r in 1..5 && c in 1..4) {
+                        val ampX = when (r) {
+                            1, 2 -> 0.048f
+                            3 -> 0.042f
+                            4 -> 0.028f
+                            else -> 0.036f
+                        }
+                        val ampY = when (r) {
+                            1, 2 -> 0.028f
+                            3 -> 0.020f
+                            4 -> 0.022f
+                            else -> 0.016f
+                        }
+                        val d = orbit(c, r, ampX, ampY)
+                        Offset(
+                            x = (baseU + d.x).coerceIn(0.04f, 0.96f),
+                            y = (baseV + d.y).coerceIn(0.05f, 0.95f),
+                        )
+                    } else {
+                        Offset(baseU, baseV)
+                    }
+                    setVertex(r, c, offset, gridColors[r][c])
+                }
+            }
+        }
+    }
+}
+
+/**
+ * A small static mesh gradient for the Gemini spark button: a pink → purple → blue diagonal
+ * built from a 2x2-cell mesh (3x3 vertices) with bicubic colour blending. This reproduces the
+ * Figma diagonal fill without a linear gradient, keeping the screen mesh-only.
+ */
+@Composable
+fun rememberUserInputSparkMeshGradientPainter(): MeshGradientPainter {
+    val pink = Color(0xFFF96BD6)
+    val pinkPurple = Color(0xFFC072EA)
+    val purple = Color(0xFF9378FF)
+    val purpleBlue = Color(0xFF585CFF)
+    val blue = Color(0xFF1E40FF)
+
+    return remember {
+        val positions = floatArrayOf(0f, 0.5f, 1f)
+        val colors = arrayOf(
+            arrayOf(pink, pinkPurple, purple),
+            arrayOf(pinkPurple, purple, purpleBlue),
+            arrayOf(purple, purpleBlue, blue),
+        )
+        MeshGradientPainter(
+            rows = 2,
+            columns = 2,
+            hasBicubicColor = true,
+        ) {
+            for (r in 0..2) {
+                for (c in 0..2) {
+                    setVertex(r, c, Offset(positions[c], positions[r]), colors[r][c])
+                }
+            }
+        }
+    }
+}