packages/SystemUI/src/com/android/systemui/statusbar/phone/NavBarTintController.java

/*
 * Copyright (C) 2018 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.systemui.statusbar.phone;

import static android.view.Display.DEFAULT_DISPLAY;
import static android.view.WindowManagerPolicyConstants.NAV_BAR_MODE_3BUTTON;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Point;
import android.graphics.Rect;
import android.os.Handler;
import android.view.CompositionSamplingListener;
import android.view.View;

import com.android.systemui.R;
import com.android.systemui.shared.system.QuickStepContract;

import java.io.PrintWriter;

/**
 * Updates the nav bar tint based on the color of the content behind the nav bar.
 */
public class NavBarTintController implements View.OnAttachStateChangeListener,
        View.OnLayoutChangeListener {

    public static final int MIN_COLOR_ADAPT_TRANSITION_TIME = 400;
    public static final int DEFAULT_COLOR_ADAPT_TRANSITION_TIME = 1700;

    private final Handler mHandler = new Handler();
    private final NavigationBarView mNavigationBarView;
    private final LightBarTransitionsController mLightBarController;
    private int mNavBarMode = NAV_BAR_MODE_3BUTTON;
    private boolean mWindowVisible;

    private final CompositionSamplingListener mSamplingListener;
    private final Runnable mUpdateSamplingListener = this::updateSamplingListener;
    private final Rect mSamplingBounds = new Rect();
    private boolean mSamplingEnabled = false;
    private boolean mSamplingListenerRegistered = false;

    private float mLastMedianLuma;
    private float mCurrentMedianLuma;
    private boolean mUpdateOnNextDraw;

    private final int mNavBarHeight;
    private final int mNavColorSampleMargin;

    // Passing the threshold of this luminance value will make the button black otherwise white
    private final float mLuminanceThreshold;
    private final float mLuminanceChangeThreshold;

    public NavBarTintController(NavigationBarView navigationBarView,
            LightBarTransitionsController lightBarController) {
        mSamplingListener = new CompositionSamplingListener(
                navigationBarView.getContext().getMainExecutor()) {
            @Override
            public void onSampleCollected(float medianLuma) {
                updateTint(medianLuma);
            }
        };
        mNavigationBarView = navigationBarView;
        mNavigationBarView.addOnAttachStateChangeListener(this);
        mNavigationBarView.addOnLayoutChangeListener(this);
        mLightBarController = lightBarController;

        final Resources res = navigationBarView.getResources();
        mNavBarHeight = res.getDimensionPixelSize(R.dimen.navigation_bar_height);
        mNavColorSampleMargin =
                res.getDimensionPixelSize(R.dimen.navigation_handle_sample_horizontal_margin);
        mLuminanceThreshold = res.getFloat(R.dimen.navigation_luminance_threshold);
        mLuminanceChangeThreshold = res.getFloat(R.dimen.navigation_luminance_change_threshold);
    }

    void onDraw() {
        if (mUpdateOnNextDraw) {
            mUpdateOnNextDraw = false;
            requestUpdateSamplingListener();
        }
    }

    void start() {
        if (!isEnabled(mNavigationBarView.getContext(), mNavBarMode)) {
            return;
        }
        mSamplingEnabled = true;
        // Defer calling updateSamplingListener since we may have just reinflated prior to this
        requestUpdateSamplingListener();
    }

    void stop() {
        mSamplingEnabled = false;
        requestUpdateSamplingListener();
    }

    @Override
    public void onViewAttachedToWindow(View view) {
        requestUpdateSamplingListener();
    }

    @Override
    public void onViewDetachedFromWindow(View view) {
        // Defer calling updateSamplingListener the attach info has not yet been reset
        requestUpdateSamplingListener();
    }

    @Override
    public void onLayoutChange(View v, int left, int top, int right, int bottom,
            int oldLeft, int oldTop, int oldRight, int oldBottom) {
        mSamplingBounds.setEmpty();
        // TODO: Extend this to 2/3 button layout as well
        View view = mNavigationBarView.getHomeHandle().getCurrentView();
        if (view != null) {
            int[] pos = new int[2];
            view.getLocationOnScreen(pos);
            Point displaySize = new Point();
            view.getContext().getDisplay().getRealSize(displaySize);
            final Rect samplingBounds = new Rect(pos[0] - mNavColorSampleMargin,
                    displaySize.y - mNavBarHeight, pos[0] + view.getWidth() + mNavColorSampleMargin,
                    displaySize.y);
            if (!samplingBounds.equals(mSamplingBounds)) {
                mSamplingBounds.set(samplingBounds);
                requestUpdateSamplingListener();
            }
        }
    }

    private void requestUpdateSamplingListener() {
        mHandler.removeCallbacks(mUpdateSamplingListener);
        mHandler.post(mUpdateSamplingListener);
    }

    private void updateSamplingListener() {
        if (mSamplingListenerRegistered) {
            mSamplingListenerRegistered = false;
            CompositionSamplingListener.unregister(mSamplingListener);
        }
        if (mSamplingEnabled && mWindowVisible && !mSamplingBounds.isEmpty()
                && mNavigationBarView.isAttachedToWindow()) {
            if (!mNavigationBarView.getViewRootImpl().getSurfaceControl().isValid()) {
                // The view may still be attached, but the surface backing the window can be
                // destroyed, so wait until the next draw to update the listener again
                mUpdateOnNextDraw = true;
                return;
            }
            mSamplingListenerRegistered = true;
            CompositionSamplingListener.register(mSamplingListener, DEFAULT_DISPLAY,
                    mNavigationBarView.getViewRootImpl().getSurfaceControl().getHandle(),
                    mSamplingBounds);
        }
    }

    private void updateTint(float medianLuma) {
        mLastMedianLuma = medianLuma;

        // If the difference between the new luma and the current luma is larger than threshold
        // then apply the current luma, this is to prevent small changes causing colors to flicker
        if (Math.abs(mCurrentMedianLuma - mLastMedianLuma) > mLuminanceChangeThreshold) {
            if (medianLuma > mLuminanceThreshold) {
                // Black
                mLightBarController.setIconsDark(true /* dark */, true /* animate */);
            } else {
                // White
                mLightBarController.setIconsDark(false /* dark */, true /* animate */);
            }
            mCurrentMedianLuma = medianLuma;
        }
    }

    public void setWindowVisible(boolean visible) {
        mWindowVisible = visible;
        requestUpdateSamplingListener();
    }

    public void onNavigationModeChanged(int mode) {
        mNavBarMode = mode;
    }

    void dump(PrintWriter pw) {
        pw.println("NavBarTintController:");
        pw.println("  navBar isAttached: " + mNavigationBarView.isAttachedToWindow());
        pw.println("  navBar isScValid: " + (mNavigationBarView.isAttachedToWindow()
                ? mNavigationBarView.getViewRootImpl().getSurfaceControl().isValid()
                : "false"));
        pw.println("  mSamplingListenerRegistered: " + mSamplingListenerRegistered);
        pw.println("  mSamplingBounds: " + mSamplingBounds);
        pw.println("  mLastMedianLuma: " + mLastMedianLuma);
        pw.println("  mCurrentMedianLuma: " + mCurrentMedianLuma);
        pw.println("  mWindowVisible: " + mWindowVisible);
    }

    public static boolean isEnabled(Context context, int navBarMode) {
        return context.getDisplayId() == DEFAULT_DISPLAY
                && QuickStepContract.isGesturalMode(navBarMode);
    }
}