Add new PropertyTransformation DrawScale

Test: added DrawScaleTest
Bug: b/290184746
Flag: NONE
Change-Id: I5f7107eb5b976ee9541a6ff7088cc2fa6c6a5b76

7 files changed, 200 insertions, 4 deletions

diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt
index eb10afc1ee57..aae61bd0f554 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt
@@ -33,7 +33,9 @@ import androidx.compose.ui.composed
 import androidx.compose.ui.draw.drawWithContent
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.isSpecified
+import androidx.compose.ui.geometry.isUnspecified
 import androidx.compose.ui.geometry.lerp
+import androidx.compose.ui.graphics.drawscope.scale
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.layout.IntermediateMeasureScope
 import androidx.compose.ui.layout.Measurable
@@ -85,6 +87,9 @@ internal class Element(val key: ElementKey) {
         /** The size of this element. */
         var size = SizeUnspecified
 
+        /** The draw scale of this element. */
+        var drawScale = Scale.Default
+
         /** The alpha of this element. */
         var alpha = AlphaUnspecified
     }
@@ -110,6 +115,13 @@ internal class Element(val key: ElementKey) {
     }
 }
 
+data class Scale(val scaleX: Float, val scaleY: Float, val pivot: Offset = Offset.Unspecified) {
+
+    companion object {
+        val Default = Scale(1f, 1f, Offset.Unspecified)
+    }
+}
+
 /** The implementation of [SceneScope.element]. */
 @OptIn(ExperimentalComposeUiApi::class)
 internal fun Modifier.element(
@@ -160,9 +172,24 @@ internal fun Modifier.element(
         }
     }
 
+    val drawScale by
+        remember(layoutImpl, element, scene, sceneValues) {
+            derivedStateOf { getDrawScale(layoutImpl, element, scene, sceneValues) }
+        }
+
     drawWithContent {
             if (shouldDrawElement(layoutImpl, scene, element)) {
-                drawContent()
+                if (drawScale == Scale.Default) {
+                    this@drawWithContent.drawContent()
+                } else {
+                    scale(
+                        drawScale.scaleX,
+                        drawScale.scaleY,
+                        if (drawScale.pivot.isUnspecified) center else drawScale.pivot
+                    ) {
+                        this@drawWithContent.drawContent()
+                    }
+                }
             }
         }
         .modifierTransformations(layoutImpl, scene, element, sceneValues)
@@ -377,6 +404,28 @@ private fun IntermediateMeasureScope.measure(
     return placeable
 }
 
+private fun getDrawScale(
+    layoutImpl: SceneTransitionLayoutImpl,
+    element: Element,
+    scene: Scene,
+    sceneValues: Element.TargetValues
+): Scale {
+    return computeValue(
+        layoutImpl,
+        scene,
+        element,
+        sceneValue = { Scale.Default },
+        transformation = { it.drawScale },
+        idleValue = Scale.Default,
+        currentValue = { Scale.Default },
+        lastValue = {
+            sceneValues.lastValues.drawScale.takeIf { it != Scale.Default }
+                ?: element.lastSharedValues.drawScale
+        },
+        ::lerp,
+    )
+}
+
 @OptIn(ExperimentalComposeUiApi::class)
 private fun IntermediateMeasureScope.place(
     layoutImpl: SceneTransitionLayoutImpl,
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitions.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitions.kt
index b163a2a96039..72a2d612d8e3 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitions.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitions.kt
@@ -25,6 +25,7 @@ import androidx.compose.ui.util.fastForEach
 import androidx.compose.ui.util.fastMap
 import com.android.compose.animation.scene.transformation.AnchoredSize
 import com.android.compose.animation.scene.transformation.AnchoredTranslate
+import com.android.compose.animation.scene.transformation.DrawScale
 import com.android.compose.animation.scene.transformation.EdgeTranslate
 import com.android.compose.animation.scene.transformation.Fade
 import com.android.compose.animation.scene.transformation.ModifierTransformation
@@ -126,6 +127,7 @@ data class TransitionSpec(
         val modifier = mutableListOf<ModifierTransformation>()
         var offset: PropertyTransformation<Offset>? = null
         var size: PropertyTransformation<IntSize>? = null
+        var drawScale: PropertyTransformation<Scale>? = null
         var alpha: PropertyTransformation<Float>? = null
 
         fun <T> onPropertyTransformation(
@@ -144,6 +146,10 @@ data class TransitionSpec(
                     throwIfNotNull(size, element, name = "size")
                     size = root as PropertyTransformation<IntSize>
                 }
+                is DrawScale -> {
+                    throwIfNotNull(drawScale, element, name = "drawScale")
+                    drawScale = root as PropertyTransformation<Scale>
+                }
                 is Fade -> {
                     throwIfNotNull(alpha, element, name = "alpha")
                     alpha = root as PropertyTransformation<Float>
@@ -167,7 +173,7 @@ data class TransitionSpec(
             }
         }
 
-        return ElementTransformations(shared, modifier, offset, size, alpha)
+        return ElementTransformations(shared, modifier, offset, size, drawScale, alpha)
     }
 
     private fun throwIfNotNull(
@@ -187,5 +193,6 @@ internal class ElementTransformations(
     val modifier: List<ModifierTransformation>,
     val offset: PropertyTransformation<Offset>?,
     val size: PropertyTransformation<IntSize>?,
+    val drawScale: PropertyTransformation<Scale>?,
     val alpha: PropertyTransformation<Float>?,
 )
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
index 7b7ddfa5ec4e..ca66dff5e231 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
@@ -17,6 +17,7 @@
 package com.android.compose.animation.scene
 
 import androidx.compose.animation.core.AnimationSpec
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.RectangleShape
 import androidx.compose.ui.graphics.Shape
 import androidx.compose.ui.unit.Dp
@@ -224,12 +225,22 @@ interface PropertyTransformationBuilder {
     /**
      * Scale the [width] and [height] of the element(s) matching [matcher]. Note that this scaling
      * is done during layout, so it will potentially impact the size and position of other elements.
-     *
-     * TODO(b/290184746): Also provide a scaleDrawing() to scale an element at drawing time.
      */
     fun scaleSize(matcher: ElementMatcher, width: Float = 1f, height: Float = 1f)
 
     /**
+     * Scale the drawing with [scaleX] and [scaleY] of the element(s) matching [matcher]. Note this
+     * will only scale the draw inside of an element, therefore it won't impact layout of elements
+     * around it.
+     */
+    fun scaleDraw(
+        matcher: ElementMatcher,
+        scaleX: Float = 1f,
+        scaleY: Float = 1f,
+        pivot: Offset = Offset.Unspecified
+    )
+
+    /**
      * Scale the element(s) matching [matcher] so that it grows/shrinks to the same size as [anchor]
      * .
      *
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDslImpl.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDslImpl.kt
index d2bfd91842ae..d4909892f492 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDslImpl.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDslImpl.kt
@@ -21,10 +21,12 @@ import androidx.compose.animation.core.DurationBasedAnimationSpec
 import androidx.compose.animation.core.Spring
 import androidx.compose.animation.core.VectorConverter
 import androidx.compose.animation.core.spring
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Shape
 import androidx.compose.ui.unit.Dp
 import com.android.compose.animation.scene.transformation.AnchoredSize
 import com.android.compose.animation.scene.transformation.AnchoredTranslate
+import com.android.compose.animation.scene.transformation.DrawScale
 import com.android.compose.animation.scene.transformation.EdgeTranslate
 import com.android.compose.animation.scene.transformation.Fade
 import com.android.compose.animation.scene.transformation.PropertyTransformation
@@ -178,6 +180,10 @@ internal class TransitionBuilderImpl : TransitionBuilder {
         transformation(ScaleSize(matcher, width, height))
     }
 
+    override fun scaleDraw(matcher: ElementMatcher, scaleX: Float, scaleY: Float, pivot: Offset) {
+        transformation(DrawScale(matcher, scaleX, scaleY, pivot))
+    }
+
     override fun anchoredSize(matcher: ElementMatcher, anchor: ElementKey) {
         transformation(AnchoredSize(matcher, anchor))
     }
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/transformation/DrawScale.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/transformation/DrawScale.kt
new file mode 100644
index 000000000000..d1cf8ee6ad4a
--- /dev/null
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/transformation/DrawScale.kt
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2023 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
+ *
+ *      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 com.android.compose.animation.scene.transformation
+
+import androidx.compose.ui.geometry.Offset
+import com.android.compose.animation.scene.Element
+import com.android.compose.animation.scene.ElementMatcher
+import com.android.compose.animation.scene.Scale
+import com.android.compose.animation.scene.Scene
+import com.android.compose.animation.scene.SceneTransitionLayoutImpl
+import com.android.compose.animation.scene.TransitionState
+
+/**
+ * Scales the draw size of an element. Note this will only scale the draw inside of an element,
+ * therefore it won't impact layout of elements around it.
+ */
+internal class DrawScale(
+    override val matcher: ElementMatcher,
+    private val scaleX: Float,
+    private val scaleY: Float,
+    private val pivot: Offset = Offset.Unspecified,
+) : PropertyTransformation<Scale> {
+
+    override fun transform(
+        layoutImpl: SceneTransitionLayoutImpl,
+        scene: Scene,
+        element: Element,
+        sceneValues: Element.TargetValues,
+        transition: TransitionState.Transition,
+        value: Scale,
+    ): Scale {
+        return Scale(scaleX, scaleY, pivot)
+    }
+}
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/ui/util/MathHelpers.kt b/packages/SystemUI/compose/scene/src/com/android/compose/ui/util/MathHelpers.kt
index eb1a634ff491..13747b72724e 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/ui/util/MathHelpers.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/ui/util/MathHelpers.kt
@@ -17,7 +17,10 @@
 
 package com.android.compose.ui.util
 
+import androidx.compose.ui.geometry.isSpecified
+import androidx.compose.ui.geometry.lerp
 import androidx.compose.ui.unit.IntSize
+import com.android.compose.animation.scene.Scale
 import kotlin.math.roundToInt
 import kotlin.math.roundToLong
 
@@ -43,3 +46,19 @@ fun lerp(start: IntSize, stop: IntSize, fraction: Float): IntSize {
         lerp(start.height, stop.height, fraction)
     )
 }
+
+/** Linearly interpolate between [start] and [stop] with [fraction] fraction between them. */
+fun lerp(start: Scale, stop: Scale, fraction: Float): Scale {
+    val pivot =
+        when {
+            start.pivot.isSpecified && stop.pivot.isSpecified ->
+                lerp(start.pivot, stop.pivot, fraction)
+            start.pivot.isSpecified -> start.pivot
+            else -> stop.pivot
+        }
+    return Scale(
+        lerp(start.scaleX, stop.scaleX, fraction),
+        lerp(start.scaleY, stop.scaleY, fraction),
+        pivot
+    )
+}
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/ui/util/MathHelpersTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/ui/util/MathHelpersTest.kt
new file mode 100644
index 000000000000..3ec73c793049
--- /dev/null
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/ui/util/MathHelpersTest.kt
@@ -0,0 +1,56 @@
+package com.android.compose.ui.util
+
+import androidx.compose.ui.geometry.Offset
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.android.compose.animation.scene.Scale
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class MathHelpersTest {
+
+    @Test
+    fun lerpScaleWithPivotUnspecified() {
+        val scale1 = Scale(1f, 1f)
+        val scale2 = Scale(5f, 3f)
+        val expectedScale = Scale(3f, 2f)
+
+        val actualScale = lerp(scale1, scale2, 0.5f)
+
+        assertThat(actualScale).isEqualTo(expectedScale)
+    }
+
+    @Test
+    fun lerpScaleWithFirstPivotSpecified() {
+        val scale1 = Scale(1f, 1f, Offset(1f, 1f))
+        val scale2 = Scale(5f, 3f)
+        val expectedScale = Scale(3f, 2f, Offset(1f, 1f))
+
+        val actualScale = lerp(scale1, scale2, 0.5f)
+
+        assertThat(actualScale).isEqualTo(expectedScale)
+    }
+
+    @Test
+    fun lerpScaleWithSecondPivotSpecified() {
+        val scale1 = Scale(1f, 1f)
+        val scale2 = Scale(5f, 3f, Offset(1f, 1f))
+        val expectedScale = Scale(3f, 2f, Offset(1f, 1f))
+
+        val actualScale = lerp(scale1, scale2, 0.5f)
+
+        assertThat(actualScale).isEqualTo(expectedScale)
+    }
+
+    @Test
+    fun lerpScaleWithBothPivotsSpecified() {
+        val scale1 = Scale(1f, 1f, Offset(1f, 1f))
+        val scale2 = Scale(5f, 3f, Offset(3f, 5f))
+        val expectedScale = Scale(3f, 2f, Offset(2f, 3f))
+
+        val actualScale = lerp(scale1, scale2, 0.5f)
+
+        assertThat(actualScale).isEqualTo(expectedScale)
+    }
+}