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Commit ff532540 authored by Jeff Brown's avatar Jeff Brown
Browse files

Improve the screen dim duration calculation. 

Take into account whether the screen off timeout is very short.
If so, we use a shorter dim timeout.  Don't allow the dim
time to be more than 20% of the total screen on time so that
the screen remains bright at least 80% of the time even when
the timeout is short.

Bug: 7273646
Change-Id: Iccea764b90f0d8b1df7009d26160c6bcf6eabe5b
parent f3fb8952

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

+17 −4
Original line number Diff line number Diff line
@@ -130,11 +130,17 @@ public final class PowerManagerService extends IPowerManager.Stub 
    private static final int DEFAULT_SCREEN_OFF_TIMEOUT = 15 * 1000;

    private static final int MINIMUM_SCREEN_OFF_TIMEOUT = 10 * 1000;



    // The screen dim duration, in seconds.

    // The screen dim duration, in milliseconds.

    // This is subtracted from the end of the screen off timeout so the

    // minimum screen off timeout should be longer than this.

    private static final int SCREEN_DIM_DURATION = 7 * 1000;



    // The maximum screen dim time expressed as a ratio relative to the screen

    // off timeout.  If the screen off timeout is very short then we want the

    // dim timeout to also be quite short so that most of the time is spent on.

    // Otherwise the user won't get much screen on time before dimming occurs.

    private static final float MAXIMUM_SCREEN_DIM_RATIO = 0.2f;



    // Upper bound on the battery charge percentage in order to consider turning

    // the screen on when the device starts charging wirelessly.

    // See point of use for more details.
@@ -1168,7 +1174,7 @@ public final class PowerManagerService extends IPowerManager.Stub 
            long nextTimeout = 0;

            if (mWakefulness != WAKEFULNESS_ASLEEP) {

                final int screenOffTimeout = getScreenOffTimeoutLocked();

                final int screenDimDuration = getScreenDimDurationLocked();

                final int screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);



                mUserActivitySummary = 0;

                if (mLastUserActivityTime >= mLastWakeTime) {
@@ -1242,8 +1248,9 @@ public final class PowerManagerService extends IPowerManager.Stub 
        return Math.max(timeout, MINIMUM_SCREEN_OFF_TIMEOUT);

    }



    private int getScreenDimDurationLocked() {

        return SCREEN_DIM_DURATION;

    private int getScreenDimDurationLocked(int screenOffTimeout) {

        return Math.min(SCREEN_DIM_DURATION,

                (int)(screenOffTimeout * MAXIMUM_SCREEN_DIM_RATIO));

    }



    /**
@@ -1987,6 +1994,12 @@ public final class PowerManagerService extends IPowerManager.Stub 
            pw.println("  mScreenBrightnessSettingMaximum=" + mScreenBrightnessSettingMaximum);

            pw.println("  mScreenBrightnessSettingDefault=" + mScreenBrightnessSettingDefault);



            final int screenOffTimeout = getScreenOffTimeoutLocked();

            final int screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);

            pw.println();

            pw.println("Screen off timeout: " + screenOffTimeout + " ms");

            pw.println("Screen dim duration: " + screenDimDuration + " ms");



            pw.println();

            pw.println("Wake Locks: size=" + mWakeLocks.size());

            for (WakeLock wl : mWakeLocks) {