src/com/android/launcher3/LauncherRootView.java

package com.android.launcher3;

import static com.android.launcher3.config.FeatureFlags.SEPARATE_RECENTS_ACTIVITY;

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.os.Build;
import android.util.AttributeSet;
import android.view.ViewDebug;
import android.view.WindowInsets;

import com.android.launcher3.graphics.SysUiScrim;
import com.android.launcher3.statemanager.StatefulActivity;

import java.util.Collections;
import java.util.List;

public class LauncherRootView extends InsettableFrameLayout {

    private final Rect mTempRect = new Rect();

    private final StatefulActivity mActivity;

    @ViewDebug.ExportedProperty(category = "launcher")
    private static final List<Rect> SYSTEM_GESTURE_EXCLUSION_RECT =
            Collections.singletonList(new Rect());

    private WindowStateListener mWindowStateListener;
    @ViewDebug.ExportedProperty(category = "launcher")
    private boolean mDisallowBackGesture;
    @ViewDebug.ExportedProperty(category = "launcher")
    private boolean mForceHideBackArrow;

    private SysUiScrim mSysUiScrim;

    public LauncherRootView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mActivity = StatefulActivity.fromContext(context);
    }

    private void handleSystemWindowInsets(Rect insets) {
        DeviceProfile dp = mActivity.getDeviceProfile();

        // Taskbar provides insets, but we don't want that for most Launcher elements so remove it.
        mTempRect.set(insets);
        insets = mTempRect;
        insets.bottom = Math.max(0, insets.bottom - dp.nonOverlappingTaskbarInset);

        // Update device profile before notifying the children.
        dp.updateInsets(insets);
        boolean resetState = !insets.equals(mInsets);
        setInsets(insets);

        if (resetState) {
            mActivity.getStateManager().reapplyState(true /* cancelCurrentAnimation */);
        }
    }

    @Override
    public WindowInsets onApplyWindowInsets(WindowInsets insets) {
        mTempRect.set(insets.getSystemWindowInsetLeft(), insets.getSystemWindowInsetTop(),
                insets.getSystemWindowInsetRight(), insets.getSystemWindowInsetBottom());
        handleSystemWindowInsets(mTempRect);
        return insets;
    }

    @Override
    public void setInsets(Rect insets) {
        // If the insets haven't changed, this is a no-op. Avoid unnecessary layout caused by
        // modifying child layout params.
        if (!insets.equals(mInsets)) {
            super.setInsets(insets);
        }
    }

    public void dispatchInsets() {
        mActivity.getDeviceProfile().updateInsets(mInsets);
        super.setInsets(mInsets);
    }

    public void setWindowStateListener(WindowStateListener listener) {
        mWindowStateListener = listener;
    }

    @Override
    public void onWindowFocusChanged(boolean hasWindowFocus) {
        super.onWindowFocusChanged(hasWindowFocus);
        if (mWindowStateListener != null) {
            mWindowStateListener.onWindowFocusChanged(hasWindowFocus);
        }
    }

    @Override
    protected void onWindowVisibilityChanged(int visibility) {
        super.onWindowVisibilityChanged(visibility);
        if (mWindowStateListener != null) {
            mWindowStateListener.onWindowVisibilityChanged(visibility);
        }
    }

    public void setSysUiScrim(SysUiScrim scrim) {
        mSysUiScrim = scrim;
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        if (mSysUiScrim != null) {
            mSysUiScrim.draw(canvas);
        }
        super.dispatchDraw(canvas);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        SYSTEM_GESTURE_EXCLUSION_RECT.get(0).set(l, t, r, b);
        setDisallowBackGesture(mDisallowBackGesture);
    }

    @TargetApi(Build.VERSION_CODES.Q)
    public void setForceHideBackArrow(boolean forceHideBackArrow) {
        this.mForceHideBackArrow = forceHideBackArrow;
        setDisallowBackGesture(mDisallowBackGesture);
    }

    @TargetApi(Build.VERSION_CODES.Q)
    public void setDisallowBackGesture(boolean disallowBackGesture) {
        if (!Utilities.ATLEAST_Q || SEPARATE_RECENTS_ACTIVITY.get()) {
            return;
        }
        mDisallowBackGesture = disallowBackGesture;
        setSystemGestureExclusionRects((mForceHideBackArrow || mDisallowBackGesture)
                ? SYSTEM_GESTURE_EXCLUSION_RECT
                : Collections.emptyList());
    }

    public interface WindowStateListener {

        void onWindowFocusChanged(boolean hasFocus);

        void onWindowVisibilityChanged(int visibility);
    }
}