src/com/android/launcher3/MultipageCellLayout.java

/*
 * Copyright (C) 2022 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.launcher3;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;

import com.android.launcher3.celllayout.CellLayoutLayoutParams;
import com.android.launcher3.util.CellAndSpan;
import com.android.launcher3.util.GridOccupancy;

import java.util.function.Supplier;

/**
 * CellLayout that simulates a split in the middle for use in foldable devices.
 */
public class MultipageCellLayout extends CellLayout {

    private final Drawable mLeftBackground;
    private final Drawable mRightBackground;

    private View mSeam;

    private boolean mSeamWasAdded = false;

    public MultipageCellLayout(Context context) {
        this(context, null);
    }

    public MultipageCellLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MultipageCellLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mLeftBackground = getContext().getDrawable(R.drawable.bg_celllayout);
        mLeftBackground.setCallback(this);
        mLeftBackground.setAlpha(0);

        mRightBackground = getContext().getDrawable(R.drawable.bg_celllayout);
        mRightBackground.setCallback(this);
        mRightBackground.setAlpha(0);

        DeviceProfile deviceProfile = mActivity.getDeviceProfile();

        mCountX = deviceProfile.inv.numColumns * 2;
        mCountY = deviceProfile.inv.numRows;
        mSeam = new View(getContext());
        setGridSize(mCountX, mCountY);
    }

    @Override
    boolean createAreaForResize(int cellX, int cellY, int spanX, int spanY, View dragView,
            int[] direction, boolean commit) {
        // Add seam to x position
        if (cellX >= mCountX / 2) {
            cellX++;
        }
        int finalCellX = cellX;
        return simulateSeam(
                () -> super.createAreaForResize(finalCellX, cellY, spanX, spanY, dragView,
                        direction, commit));
    }

    @Override
    ItemConfiguration closestEmptySpaceReorder(int pixelX, int pixelY, int minSpanX, int minSpanY,
            int spanX, int spanY) {
        return removeSeamFromSolution(simulateSeam(
                () -> super.closestEmptySpaceReorder(pixelX, pixelY, minSpanX, minSpanY, spanX,
                        spanY)));
    }

    @Override
    protected ItemConfiguration findReorderSolution(int pixelX, int pixelY, int minSpanX,
            int minSpanY, int spanX, int spanY, int[] direction, View dragView, boolean decX,
            ItemConfiguration solution) {
        return removeSeamFromSolution(simulateSeam(
                () -> super.findReorderSolution(pixelX, pixelY, minSpanX, minSpanY, spanX, spanY,
                        direction, dragView, decX, solution)));
    }

    @Override
    public ItemConfiguration dropInPlaceSolution(int pixelX, int pixelY, int spanX, int spanY,
            View dragView) {
        return removeSeamFromSolution(simulateSeam(
                () -> super.dropInPlaceSolution(pixelX, pixelY, spanX, spanY, dragView)));
    }

    void addSeam() {
        CellLayoutLayoutParams lp = new CellLayoutLayoutParams(mCountX / 2, 0, 1, mCountY);
        mSeamWasAdded = true;
        lp.canReorder = false;
        mCountX++;
        mShortcutsAndWidgets.addViewInLayout(mSeam, lp);
        mOccupied = createGridOccupancyWithSeam(mOccupied);
        mTmpOccupied = new GridOccupancy(mCountX, mCountY);
    }

    void removeSeam() {
        mCountX--;
        mShortcutsAndWidgets.removeViewInLayout(mSeam);
        mTmpOccupied = new GridOccupancy(mCountX, mCountY);
        mSeamWasAdded = false;
    }

    protected <T> T simulateSeam(Supplier<T> f) {
        if (mSeamWasAdded) {
            return f.get();
        }
        GridOccupancy auxGrid = mOccupied;
        addSeam();
        T res = f.get();
        removeSeam();
        mOccupied = auxGrid;
        return res;
    }

    private ItemConfiguration removeSeamFromSolution(ItemConfiguration solution) {
        solution.map.forEach((view, cell) -> cell.cellX = cell.cellX > mCountX / 2
                ? cell.cellX - 1 : cell.cellX);
        solution.cellX = solution.cellX > mCountX / 2 ? solution.cellX - 1 : solution.cellX;
        return solution;
    }



    GridOccupancy createGridOccupancyWithSeam(GridOccupancy gridOccupancy) {
        GridOccupancy grid = new GridOccupancy(getCountX(), getCountY());
        for (int x = 0; x < getCountX(); x++) {
            for (int y = 0; y < getCountY(); y++) {
                int offset = x >= getCountX() / 2 ? 1 : 0;
                if (x == getCountX() / 2) {
                    grid.cells[x][y] = true;
                } else {
                    grid.cells[x][y] = gridOccupancy.cells[x - offset][y];
                }
            }
        }
        return grid;
    }

    @Override
    protected void copyCurrentStateToSolution(ItemConfiguration solution, boolean temp) {
        int childCount = mShortcutsAndWidgets.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = mShortcutsAndWidgets.getChildAt(i);
            CellLayoutLayoutParams lp = (CellLayoutLayoutParams) child.getLayoutParams();
            int seamOffset = lp.getCellX() >= mCountX / 2 && lp.canReorder ? 1 : 0;
            CellAndSpan c = new CellAndSpan(lp.getCellX() + seamOffset, lp.getCellY(), lp.cellHSpan,
                    lp.cellVSpan);
            solution.add(child, c);
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (mLeftBackground.getAlpha() > 0) {
            mLeftBackground.setState(mBackground.getState());
            mLeftBackground.draw(canvas);
        }
        if (mRightBackground.getAlpha() > 0) {
            mRightBackground.setState(mBackground.getState());
            mRightBackground.draw(canvas);
        }

        super.onDraw(canvas);
    }

    @Override
    protected void updateBgAlpha() {
        mLeftBackground.setAlpha((int) (mSpringLoadedProgress * 255));
        mRightBackground.setAlpha((int) (mSpringLoadedProgress * 255));
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        Rect rect = mBackground.getBounds();
        mLeftBackground.setBounds(rect.left, rect.top, rect.right / 2 - 20, rect.bottom);
        mRightBackground.setBounds(rect.right / 2 + 20, rect.top, rect.right, rect.bottom);
    }
}