Set backlight brightness in correct order.

Disable backlight before turning off the screen.
Enable backlight after turning on the screen.

Bug: 7016215
Change-Id: Idb763f85f7a40e852483c57e0a0d1b27eb943f08

Author: Jeff Brown

services/java/com/android/server/power/DisplayPowerState.java

@@ -239,22 +239,24 @@ private void invalidate(int dirty) {
     private void apply() {
         if (mDirty != 0) {
             if ((mDirty & DIRTY_SCREEN_ON) != 0 && !mScreenOn) {
+                mScreenBrightnessModulator.setBrightness(0, true /*sync*/);
                 PowerManagerService.nativeSetScreenState(false);
             }
 
             if ((mDirty & DIRTY_ELECTRON_BEAM) != 0) {
                 mElectronBeam.draw(mElectronBeamLevel);
             }
 
-            if ((mDirty & (DIRTY_BRIGHTNESS | DIRTY_SCREEN_ON | DIRTY_ELECTRON_BEAM)) != 0) {
-                mScreenBrightnessModulator.setBrightness(mScreenOn ?
-                        (int)(mScreenBrightness * mElectronBeamLevel) : 0);
-            }
-
             if ((mDirty & DIRTY_SCREEN_ON) != 0 && mScreenOn) {
                 PowerManagerService.nativeSetScreenState(true);
             }
 
+            if ((mDirty & (DIRTY_BRIGHTNESS | DIRTY_SCREEN_ON | DIRTY_ELECTRON_BEAM)) != 0
+                    && mScreenOn) {
+                mScreenBrightnessModulator.setBrightness(
+                        (int)(mScreenBrightness * mElectronBeamLevel), false /*sync*/);
+            }
+
             mDirty = 0;
 
             if (mCleanListener != null) {

services/java/com/android/server/power/PhotonicModulator.java

@@ -49,11 +49,12 @@ public PhotonicModulator(Executor executor, LightsService.Light light,
     }
 
     /**
-     * Asynchronously sets the backlight brightness.
+     * Sets the backlight brightness, synchronously or asynchronously.
      *
      * @param lightValue The new light value, from 0 to 255.
+     * @param sync If true, waits for the brightness change to complete before returning.
      */
-    public void setBrightness(int lightValue) {
+    public void setBrightness(int lightValue, boolean sync) {
         synchronized (mLock) {
             if (lightValue != mPendingLightValue) {
                 mPendingLightValue = lightValue;
@@ -63,6 +64,15 @@ public void setBrightness(int lightValue) {
                     mExecutor.execute(mTask);
                 }
             }
+            if (sync) {
+                while (mPendingChange) {
+                    try {
+                        mLock.wait();
+                    } catch (InterruptedException ex) {
+                        // ignore it
+                    }
+                }
+            }
         }
     }
 
@@ -76,6 +86,7 @@ public void run() {
                     if (newLightValue == mActualLightValue) {
                         mSuspendBlocker.release();
                         mPendingChange = false;
+                        mLock.notifyAll();
                         return;
                     }
                     mActualLightValue = newLightValue;