Only call saveLayerAlpha when alpha is not at max or min values

Bug: 282226587
Bug: 282677494
Bug: 282769559
Test: Checked use cases on device
Change-Id: Id8dd5c61db6b654c30ebeba32d9d16e83c76c55c

4 files changed, 31 insertions, 14 deletions

diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardClockFrame.kt b/packages/SystemUI/src/com/android/keyguard/KeyguardClockFrame.kt
index d821d309adde..635f0fa44234 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardClockFrame.kt
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardClockFrame.kt
@@ -18,14 +18,24 @@ class KeyguardClockFrame(
     }
 
     protected override fun dispatchDraw(canvas: Canvas) {
-        val restoreTo = saveCanvasAlpha(this, canvas, drawAlpha)
-        super.dispatchDraw(canvas)
-        canvas.restoreToCount(restoreTo)
+        saveCanvasAlpha(this, canvas, drawAlpha) { super.dispatchDraw(it) }
     }
 
     companion object {
         @JvmStatic
-        fun saveCanvasAlpha(view: View, canvas: Canvas, alpha: Int): Int {
+        fun saveCanvasAlpha(view: View, canvas: Canvas, alpha: Int, drawFunc: (Canvas) -> Unit) {
+            if (alpha <= 0) {
+                // Zero Alpha -> skip drawing phase
+                return
+            }
+
+            if (alpha >= 255) {
+                // Max alpha -> no need for layer
+                drawFunc(canvas)
+                return
+            }
+
+            // Find x & y of view on screen
             var (x, y) =
                 run {
                     val locationOnScreen = IntArray(2)
@@ -33,7 +43,10 @@ class KeyguardClockFrame(
                     Pair(locationOnScreen[0].toFloat(), locationOnScreen[1].toFloat())
                 }
 
-            return canvas.saveLayerAlpha(-1f * x, -1f * y, x + view.width, y + view.height, alpha)
+            val restoreTo =
+                canvas.saveLayerAlpha(-1f * x, -1f * y, x + view.width, y + view.height, alpha)
+            drawFunc(canvas)
+            canvas.restoreToCount(restoreTo)
         }
     }
 }
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
index 05a8f9fc9ae2..e54d4739dc97 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
@@ -130,9 +130,12 @@ public class KeyguardClockSwitch extends RelativeLayout {
 
     @Override
     protected void dispatchDraw(Canvas canvas) {
-        int restoreTo = KeyguardClockFrame.saveCanvasAlpha(this, canvas, mDrawAlpha);
-        super.dispatchDraw(canvas);
-        canvas.restoreToCount(restoreTo);
+        KeyguardClockFrame.saveCanvasAlpha(
+                this, canvas, mDrawAlpha,
+                c -> {
+                    super.dispatchDraw(c);
+                    return kotlin.Unit.INSTANCE;
+                });
     }
 
     public void setLogBuffer(LogBuffer logBuffer) {
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusContainer.kt b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusContainer.kt
index d885892ec0ab..298eff27060b 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusContainer.kt
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusContainer.kt
@@ -17,8 +17,6 @@ class KeyguardStatusContainer(
     }
 
     protected override fun dispatchDraw(canvas: Canvas) {
-        val restoreTo = KeyguardClockFrame.saveCanvasAlpha(this, canvas, drawAlpha)
-        super.dispatchDraw(canvas)
-        canvas.restoreToCount(restoreTo)
+        KeyguardClockFrame.saveCanvasAlpha(this, canvas, drawAlpha) { super.dispatchDraw(canvas) }
     }
 }
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusView.java b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusView.java
index 553af5b8fa41..a6252a39ee8a 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusView.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusView.java
@@ -146,8 +146,11 @@ public class KeyguardStatusView extends GridLayout {
 
     @Override
     protected void dispatchDraw(Canvas canvas) {
-        int restoreTo = KeyguardClockFrame.saveCanvasAlpha(this, canvas, mDrawAlpha);
-        super.dispatchDraw(canvas);
-        canvas.restoreToCount(restoreTo);
+        KeyguardClockFrame.saveCanvasAlpha(
+                this, canvas, mDrawAlpha,
+                c -> {
+                    super.dispatchDraw(c);
+                    return kotlin.Unit.INSTANCE;
+                });
     }
 }