Scale Launcher folders on hover.

Bug: 243191650
Test: PreviewBackgroundTest
Flag: ENABLE_CURSOR_HOVER_STATES
Change-Id: I8035501203af5c2d97b62cc79e576303e57f8b99
diff --git a/src/com/android/launcher3/folder/FolderIcon.java b/src/com/android/launcher3/folder/FolderIcon.java
index d78bfba..53d0efb 100644
--- a/src/com/android/launcher3/folder/FolderIcon.java
+++ b/src/com/android/launcher3/folder/FolderIcon.java
@@ -16,6 +16,7 @@
 
 package com.android.launcher3.folder;
 
+import static com.android.launcher3.config.FeatureFlags.ENABLE_CURSOR_HOVER_STATES;
 import static com.android.launcher3.folder.ClippedFolderIconLayoutRule.ICON_OVERLAP_FACTOR;
 import static com.android.launcher3.folder.ClippedFolderIconLayoutRule.MAX_NUM_ITEMS_IN_PREVIEW;
 import static com.android.launcher3.folder.PreviewItemManager.INITIAL_ITEM_ANIMATION_DURATION;
@@ -627,7 +628,7 @@
             Utilities.scaleRectAboutCenter(iconBounds, iconScale);
 
             // If we are animating to the accepting state, animate the dot out.
-            mDotParams.scale = Math.max(0, mDotScale - mBackground.getScaleProgress());
+            mDotParams.scale = Math.max(0, mDotScale - mBackground.getAcceptScaleProgress());
             mDotParams.dotColor = mBackground.getDotColor();
             mDotRenderer.draw(canvas, mDotParams);
         }
@@ -801,6 +802,14 @@
         }
     }
 
+    @Override
+    public void onHoverChanged(boolean hovered) {
+        super.onHoverChanged(hovered);
+        if (ENABLE_CURSOR_HOVER_STATES.get()) {
+            mBackground.setHovered(hovered);
+        }
+    }
+
     /**
      * Interface that provides callbacks to a parent ViewGroup that hosts this FolderIcon.
      */
diff --git a/src/com/android/launcher3/folder/PreviewBackground.java b/src/com/android/launcher3/folder/PreviewBackground.java
index 406955c..b320ceb 100644
--- a/src/com/android/launcher3/folder/PreviewBackground.java
+++ b/src/com/android/launcher3/folder/PreviewBackground.java
@@ -16,6 +16,8 @@
 
 package com.android.launcher3.folder;
 
+import static com.android.app.animation.Interpolators.ACCELERATE_DECELERATE;
+import static com.android.app.animation.Interpolators.EMPHASIZED_DECELERATE;
 import static com.android.launcher3.folder.ClippedFolderIconLayoutRule.ICON_OVERLAP_FACTOR;
 import static com.android.launcher3.graphics.IconShape.getShape;
 import static com.android.launcher3.icons.GraphicsUtils.setColorAlphaBound;
@@ -39,6 +41,9 @@
 import android.graphics.Shader;
 import android.util.Property;
 import android.view.View;
+import android.view.animation.Interpolator;
+
+import androidx.annotation.VisibleForTesting;
 
 import com.android.launcher3.CellLayout;
 import com.android.launcher3.DeviceProfile;
@@ -55,7 +60,10 @@
     private static final boolean DRAW_SHADOW = false;
     private static final boolean DRAW_STROKE = false;
 
-    private static final int CONSUMPTION_ANIMATION_DURATION = 100;
+    @VisibleForTesting protected static final int CONSUMPTION_ANIMATION_DURATION = 100;
+
+    @VisibleForTesting protected static final float HOVER_SCALE = 1.1f;
+    @VisibleForTesting protected static final int HOVER_ANIMATION_DURATION = 300;
 
     private final PorterDuffXfermode mShadowPorterDuffXfermode
             = new PorterDuffXfermode(PorterDuff.Mode.DST_OUT);
@@ -86,17 +94,21 @@
     public boolean isClipping = true;
 
     // Drawing / animation configurations
-    private static final float ACCEPT_SCALE_FACTOR = 1.20f;
+    @VisibleForTesting protected static final float ACCEPT_SCALE_FACTOR = 1.20f;
 
     // Expressed on a scale from 0 to 255.
     private static final int BG_OPACITY = 255;
     private static final int MAX_BG_OPACITY = 255;
     private static final int SHADOW_OPACITY = 40;
 
-    private ValueAnimator mScaleAnimator;
+    @VisibleForTesting protected ValueAnimator mScaleAnimator;
     private ObjectAnimator mStrokeAlphaAnimator;
     private ObjectAnimator mShadowAnimator;
 
+    @VisibleForTesting protected boolean mIsAccepting;
+    @VisibleForTesting protected boolean mIsHovered;
+    @VisibleForTesting protected boolean mIsHoveredOrAnimating;
+
     private static final Property<PreviewBackground, Integer> STROKE_ALPHA =
             new Property<PreviewBackground, Integer>(Integer.class, "strokeAlpha") {
                 @Override
@@ -203,11 +215,11 @@
     }
 
     /**
-     * Returns the progress of the scale animation, where 0 means the scale is at 1f
-     * and 1 means the scale is at ACCEPT_SCALE_FACTOR.
+     * Returns the progress of the scale animation to accept state, where 0 means the scale is at
+     * 1f and 1 means the scale is at ACCEPT_SCALE_FACTOR. Returns 0 when scaled due to hover.
      */
-    float getScaleProgress() {
-        return (mScale - 1f) / (ACCEPT_SCALE_FACTOR - 1f);
+    float getAcceptScaleProgress() {
+        return mIsHoveredOrAnimating ? 0 : (mScale - 1f) / (ACCEPT_SCALE_FACTOR - 1f);
     }
 
     void invalidate() {
@@ -385,60 +397,70 @@
         return mDrawingDelegate != null;
     }
 
-    private void animateScale(float finalScale, final Runnable onStart, final Runnable onEnd) {
-        final float scale0 = mScale;
-        final float scale1 = finalScale;
-
+    protected void animateScale(boolean isAccepting, boolean isHovered) {
         if (mScaleAnimator != null) {
             mScaleAnimator.cancel();
         }
 
-        mScaleAnimator = ValueAnimator.ofFloat(0f, 1.0f);
-
-        mScaleAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
-            @Override
-            public void onAnimationUpdate(ValueAnimator animation) {
-                float prog = animation.getAnimatedFraction();
-                mScale = prog * scale1 + (1 - prog) * scale0;
-                invalidate();
+        final float startScale = mScale;
+        final float endScale = isAccepting ? ACCEPT_SCALE_FACTOR : (isHovered ? HOVER_SCALE : 1f);
+        Interpolator interpolator =
+                isAccepting != mIsAccepting ? ACCELERATE_DECELERATE : EMPHASIZED_DECELERATE;
+        int duration = isAccepting != mIsAccepting ? CONSUMPTION_ANIMATION_DURATION
+                : HOVER_ANIMATION_DURATION;
+        mIsAccepting = isAccepting;
+        mIsHovered = isHovered;
+        if (startScale == endScale) {
+            if (!mIsAccepting) {
+                clearDrawingDelegate();
             }
+            mIsHoveredOrAnimating = mIsHovered;
+            return;
+        }
+
+
+        mScaleAnimator = ValueAnimator.ofFloat(0f, 1.0f);
+        mScaleAnimator.addUpdateListener(animation -> {
+            float prog = animation.getAnimatedFraction();
+            mScale = prog * endScale + (1 - prog) * startScale;
+            invalidate();
         });
         mScaleAnimator.addListener(new AnimatorListenerAdapter() {
             @Override
             public void onAnimationStart(Animator animation) {
-                if (onStart != null) {
-                    onStart.run();
+                if (mIsHovered) {
+                    mIsHoveredOrAnimating = true;
                 }
             }
 
             @Override
             public void onAnimationEnd(Animator animation) {
-                if (onEnd != null) {
-                    onEnd.run();
+                if (!mIsAccepting) {
+                    clearDrawingDelegate();
                 }
+                mIsHoveredOrAnimating = mIsHovered;
                 mScaleAnimator = null;
             }
         });
-
-        mScaleAnimator.setDuration(CONSUMPTION_ANIMATION_DURATION);
+        mScaleAnimator.setInterpolator(interpolator);
+        mScaleAnimator.setDuration(duration);
         mScaleAnimator.start();
     }
 
     public void animateToAccept(CellLayout cl, int cellX, int cellY) {
-        animateScale(ACCEPT_SCALE_FACTOR, () -> delegateDrawing(cl, cellX, cellY), null);
+        delegateDrawing(cl, cellX, cellY);
+        animateScale(/* isAccepting= */ true, mIsHovered);
     }
 
     public void animateToRest() {
-        // This can be called multiple times -- we need to make sure the drawing delegate
-        // is saved and restored at the beginning of the animation, since cancelling the
-        // existing animation can clear the delgate.
-        CellLayout cl = mDrawingDelegate;
-        int cellX = mDelegateCellX;
-        int cellY = mDelegateCellY;
-        animateScale(1f, () -> delegateDrawing(cl, cellX, cellY), this::clearDrawingDelegate);
+        animateScale(/* isAccepting= */ false, mIsHovered);
     }
 
     public float getStrokeWidth() {
         return mStrokeWidth;
     }
+
+    protected void setHovered(boolean hovered) {
+        animateScale(mIsAccepting, /* isHovered= */ hovered);
+    }
 }
diff --git a/tests/src/com/android/launcher3/folder/PreviewBackgroundTest.java b/tests/src/com/android/launcher3/folder/PreviewBackgroundTest.java
new file mode 100644
index 0000000..715a1f8
--- /dev/null
+++ b/tests/src/com/android/launcher3/folder/PreviewBackgroundTest.java
@@ -0,0 +1,323 @@
+/*
+ * Copyright (C) 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.launcher3.folder;
+
+import static com.android.launcher3.folder.PreviewBackground.ACCEPT_SCALE_FACTOR;
+import static com.android.launcher3.folder.PreviewBackground.CONSUMPTION_ANIMATION_DURATION;
+import static com.android.launcher3.folder.PreviewBackground.HOVER_ANIMATION_DURATION;
+import static com.android.launcher3.folder.PreviewBackground.HOVER_SCALE;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+import android.testing.AndroidTestingRunner;
+import android.testing.TestableLooper;
+import android.view.animation.AccelerateDecelerateInterpolator;
+import android.view.animation.PathInterpolator;
+
+import androidx.test.filters.SmallTest;
+
+import com.android.launcher3.CellLayout;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+@SmallTest
+@RunWith(AndroidTestingRunner.class)
+@TestableLooper.RunWithLooper(setAsMainLooper = true)
+public class PreviewBackgroundTest {
+
+    private static final float REST_SCALE = 1f;
+    private static final float EPSILON = 0.00001f;
+
+    @Mock
+    CellLayout mCellLayout;
+
+    private final PreviewBackground mPreviewBackground = new PreviewBackground();
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mPreviewBackground.mScale = REST_SCALE;
+        mPreviewBackground.mIsAccepting = false;
+        mPreviewBackground.mIsHovered = false;
+        mPreviewBackground.mIsHoveredOrAnimating = false;
+        mPreviewBackground.invalidate();
+    }
+
+    @Test
+    public void testAnimateScale_restToHovered() {
+        mPreviewBackground.setHovered(true);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                HOVER_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator() instanceof PathInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_restToNotHovered() {
+        mPreviewBackground.setHovered(false);
+
+        assertEquals("Scale changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertNull("Animator not null.", mPreviewBackground.mScaleAnimator);
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_hoveredToHovered() {
+        mPreviewBackground.mScale = HOVER_SCALE;
+        mPreviewBackground.mIsHovered = true;
+        mPreviewBackground.mIsHoveredOrAnimating = true;
+        mPreviewBackground.invalidate();
+
+        mPreviewBackground.setHovered(true);
+
+        assertEquals("Scale changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        assertNull("Animator not null.", mPreviewBackground.mScaleAnimator);
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_hoveredToRest() {
+        mPreviewBackground.mScale = HOVER_SCALE;
+        mPreviewBackground.mIsHovered = true;
+        mPreviewBackground.mIsHoveredOrAnimating = true;
+        mPreviewBackground.invalidate();
+
+        mPreviewBackground.setHovered(false);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                HOVER_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator() instanceof PathInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_restToAccept() {
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale changed.", mPreviewBackground.mScale, ACCEPT_SCALE_FACTOR, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                CONSUMPTION_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator()
+                        instanceof AccelerateDecelerateInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 1.", mPreviewBackground.getAcceptScaleProgress(), 1,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_restToRest() {
+        mPreviewBackground.animateToRest();
+
+        assertEquals("Scale changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertNull("Animator not null.", mPreviewBackground.mScaleAnimator);
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_acceptToRest() {
+        mPreviewBackground.mScale = ACCEPT_SCALE_FACTOR;
+        mPreviewBackground.mIsAccepting = true;
+        mPreviewBackground.invalidate();
+
+        mPreviewBackground.animateToRest();
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                CONSUMPTION_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator()
+                        instanceof AccelerateDecelerateInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_acceptToHover() {
+        mPreviewBackground.mScale = ACCEPT_SCALE_FACTOR;
+        mPreviewBackground.mIsAccepting = true;
+        mPreviewBackground.invalidate();
+
+        mPreviewBackground.mIsAccepting = false;
+        mPreviewBackground.setHovered(true);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                HOVER_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator() instanceof PathInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_hoverToAccept() {
+        mPreviewBackground.mScale = HOVER_SCALE;
+        mPreviewBackground.mIsHovered = true;
+        mPreviewBackground.mIsHoveredOrAnimating = true;
+        mPreviewBackground.invalidate();
+
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, ACCEPT_SCALE_FACTOR, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                CONSUMPTION_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator()
+                        instanceof AccelerateDecelerateInterpolator);
+        mPreviewBackground.mIsHovered = false;
+        endAnimation();
+        assertEquals("Scale progress not 1.", mPreviewBackground.getAcceptScaleProgress(), 1,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_midwayToHoverToAccept() {
+        mPreviewBackground.setHovered(true);
+        runAnimationToFraction(0.5f);
+        assertTrue("Scale not changed.",
+                mPreviewBackground.mScale > REST_SCALE && mPreviewBackground.mScale < HOVER_SCALE);
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, ACCEPT_SCALE_FACTOR, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                CONSUMPTION_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator()
+                        instanceof AccelerateDecelerateInterpolator);
+        mPreviewBackground.mIsHovered = false;
+        endAnimation();
+        assertEquals("Scale progress not 1.", mPreviewBackground.getAcceptScaleProgress(), 1,
+                EPSILON);
+        assertNull("Animator not null.", mPreviewBackground.mScaleAnimator);
+    }
+
+    @Test
+    public void testAnimateScale_partWayToAcceptToHover() {
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(0.25f);
+        assertTrue("Scale not changed part way.", mPreviewBackground.mScale > REST_SCALE
+                && mPreviewBackground.mScale < ACCEPT_SCALE_FACTOR);
+
+        mPreviewBackground.mIsAccepting = false;
+        mPreviewBackground.setHovered(true);
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                HOVER_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator() instanceof PathInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_midwayToAcceptEqualsHover() {
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(0.5f);
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        mPreviewBackground.mIsAccepting = false;
+
+        mPreviewBackground.setHovered(true);
+
+        assertEquals("Scale changed.", mPreviewBackground.mScale, HOVER_SCALE, EPSILON);
+        assertNull("Animator not null.", mPreviewBackground.mScaleAnimator);
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_midwayToHoverToRest() {
+        mPreviewBackground.setHovered(true);
+        runAnimationToFraction(0.5f);
+        assertTrue("Scale not changed midway.",
+                mPreviewBackground.mScale > REST_SCALE && mPreviewBackground.mScale < HOVER_SCALE);
+
+        mPreviewBackground.mIsHovered = false;
+        mPreviewBackground.animateToRest();
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                HOVER_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator() instanceof PathInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    @Test
+    public void testAnimateScale_midwayToAcceptToRest() {
+        mPreviewBackground.animateToAccept(mCellLayout, 0, 0);
+        runAnimationToFraction(0.5f);
+        assertTrue("Scale not changed.", mPreviewBackground.mScale > REST_SCALE
+                && mPreviewBackground.mScale < ACCEPT_SCALE_FACTOR);
+
+        mPreviewBackground.animateToRest();
+        runAnimationToFraction(1f);
+
+        assertEquals("Scale not changed.", mPreviewBackground.mScale, REST_SCALE, EPSILON);
+        assertEquals("Duration not correct.", mPreviewBackground.mScaleAnimator.getDuration(),
+                CONSUMPTION_ANIMATION_DURATION);
+        assertTrue("Wrong interpolator used.",
+                mPreviewBackground.mScaleAnimator.getInterpolator()
+                        instanceof AccelerateDecelerateInterpolator);
+        endAnimation();
+        assertEquals("Scale progress not 0.", mPreviewBackground.getAcceptScaleProgress(), 0,
+                EPSILON);
+    }
+
+    private void runAnimationToFraction(float animationFraction) {
+        mPreviewBackground.mScaleAnimator.setCurrentFraction(animationFraction);
+    }
+
+    private void endAnimation() {
+        mPreviewBackground.mScaleAnimator.end();
+    }
+}