lawnchair/src/com/android/launcher3/graphics/DragPreviewProvider.java

/*
 * Copyright (C) 2016 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.graphics;

import static com.android.launcher3.util.Executors.UI_HELPER_EXECUTOR;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.view.View;

import com.android.launcher3.BubbleTextView;
import com.android.launcher3.Launcher;
import com.android.launcher3.R;
import com.android.launcher3.config.FeatureFlags;
import com.android.launcher3.dragndrop.DraggableView;
import com.android.launcher3.icons.BitmapRenderer;
import com.android.launcher3.widget.LauncherAppWidgetHostView;

import java.nio.ByteBuffer;

/**
 * A utility class to generate preview bitmap for dragging.
 */
public class DragPreviewProvider {

    private final Rect mTempRect = new Rect();

    protected final View mView;

    // The padding added to the drag view during the preview generation.
    public final int previewPadding;

    public final int blurSizeOutline;

    private OutlineGeneratorCallback mOutlineGeneratorCallback;
    public Bitmap generatedDragOutline;

    public DragPreviewProvider(View view) {
        this(view, view.getContext());
    }

    public DragPreviewProvider(View view, Context context) {
        mView = view;
        blurSizeOutline =
                context.getResources().getDimensionPixelSize(R.dimen.blur_size_medium_outline);
        previewPadding = blurSizeOutline;
    }

    /**
     * Draws the {@link #mView} into the given {@param destCanvas}.
     */
    protected void drawDragView(Canvas destCanvas, float scale) {
        int saveCount = destCanvas.save();
        destCanvas.scale(scale, scale);

        if (mView instanceof DraggableView) {
            DraggableView dv = (DraggableView) mView;
            dv.prepareDrawDragView();
            dv.getSourceVisualDragBounds(mTempRect);
            destCanvas.translate(blurSizeOutline / 2 - mTempRect.left,
                    blurSizeOutline / 2 - mTempRect.top);
            mView.draw(destCanvas);
        }
        destCanvas.restoreToCount(saveCount);
    }

    /**
     * Returns a new bitmap to show when the {@link #mView} is being dragged around.
     * Responsibility for the bitmap is transferred to the caller.
     */
    public Bitmap createDragBitmap() {
        int width = 0;
        int height = 0;
        // Assume scaleX == scaleY, which is always the case for workspace items.
        float scale = mView.getScaleX();
        if (mView instanceof DraggableView) {
            ((DraggableView) mView).getSourceVisualDragBounds(mTempRect);
            width = mTempRect.width();
            height = mTempRect.height();
        } else {
            width = mView.getWidth();
            height = mView.getHeight();
        }

        return BitmapRenderer.createHardwareBitmap(width + blurSizeOutline,
                height + blurSizeOutline, (c) -> drawDragView(c, scale));
    }

    public final void generateDragOutline(Bitmap preview) {
        if (FeatureFlags.IS_STUDIO_BUILD && mOutlineGeneratorCallback != null) {
            throw new RuntimeException("Drag outline generated twice");
        }

        mOutlineGeneratorCallback = new OutlineGeneratorCallback(preview);
        UI_HELPER_EXECUTOR.post(mOutlineGeneratorCallback);
    }

    protected static Rect getDrawableBounds(Drawable d) {
        Rect bounds = new Rect();
        d.copyBounds(bounds);
        if (bounds.width() == 0 || bounds.height() == 0) {
            bounds.set(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
        } else {
            bounds.offsetTo(0, 0);
        }
        return bounds;
    }

    public float getScaleAndPosition(Bitmap preview, int[] outPos) {
        float scale = Launcher.getLauncher(mView.getContext())
                .getDragLayer().getLocationInDragLayer(mView, outPos);
        if (mView instanceof LauncherAppWidgetHostView) {
            // App widgets are technically scaled, but are drawn at their expected size -- so the
            // app widget scale should not affect the scale of the preview.
            scale /= ((LauncherAppWidgetHostView) mView).getScaleToFit();
        }

        outPos[0] = Math.round(outPos[0] -
                (preview.getWidth() - scale * mView.getWidth() * mView.getScaleX()) / 2);
        outPos[1] = Math.round(outPos[1] - (1 - scale) * preview.getHeight() / 2
                - previewPadding / 2);
        return scale;
    }

    protected Bitmap convertPreviewToAlphaBitmap(Bitmap preview) {
        return preview.copy(Bitmap.Config.ALPHA_8, true);
    }

    private class OutlineGeneratorCallback implements Runnable {

        private final Bitmap mPreviewSnapshot;
        private final Context mContext;
        private final boolean mIsIcon;

        OutlineGeneratorCallback(Bitmap preview) {
            mPreviewSnapshot = preview;
            mContext = mView.getContext();
            mIsIcon = mView instanceof BubbleTextView;
        }

        @Override
        public void run() {
            Bitmap preview = convertPreviewToAlphaBitmap(mPreviewSnapshot);
            if (mIsIcon) {
                int size = Launcher.getLauncher(mContext).getDeviceProfile().iconSizePx;
                preview = Bitmap.createScaledBitmap(preview, size, size, false);
            }
            //else case covers AppWidgetHost (doesn't drag/drop across different device profiles)

            // We start by removing most of the alpha channel so as to ignore shadows, and
            // other types of partial transparency when defining the shape of the object
            byte[] pixels = new byte[preview.getWidth() * preview.getHeight()];
            ByteBuffer buffer = ByteBuffer.wrap(pixels);
            buffer.rewind();
            preview.copyPixelsToBuffer(buffer);

            for (int i = 0; i < pixels.length; i++) {
                if ((pixels[i] & 0xFF) < 188) {
                    pixels[i] = 0;
                }
            }

            buffer.rewind();
            preview.copyPixelsFromBuffer(buffer);

            final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
            Canvas canvas = new Canvas();

            // calculate the outer blur first
            paint.setMaskFilter(new BlurMaskFilter(blurSizeOutline, BlurMaskFilter.Blur.OUTER));
            int[] outerBlurOffset = new int[2];
            Bitmap thickOuterBlur = preview.extractAlpha(paint, outerBlurOffset);

            paint.setMaskFilter(new BlurMaskFilter(
                    mContext.getResources().getDimension(R.dimen.blur_size_thin_outline),
                    BlurMaskFilter.Blur.OUTER));
            int[] brightOutlineOffset = new int[2];
            Bitmap brightOutline = preview.extractAlpha(paint, brightOutlineOffset);

            // calculate the inner blur
            canvas.setBitmap(preview);
            canvas.drawColor(0xFF000000, PorterDuff.Mode.SRC_OUT);
            paint.setMaskFilter(new BlurMaskFilter(blurSizeOutline, BlurMaskFilter.Blur.NORMAL));
            int[] thickInnerBlurOffset = new int[2];
            Bitmap thickInnerBlur = preview.extractAlpha(paint, thickInnerBlurOffset);

            // mask out the inner blur
            paint.setMaskFilter(null);
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
            canvas.setBitmap(thickInnerBlur);
            canvas.drawBitmap(preview, -thickInnerBlurOffset[0],
                    -thickInnerBlurOffset[1], paint);
            canvas.drawRect(0, 0, -thickInnerBlurOffset[0], thickInnerBlur.getHeight(), paint);
            canvas.drawRect(0, 0, thickInnerBlur.getWidth(), -thickInnerBlurOffset[1], paint);

            // draw the inner and outer blur
            paint.setXfermode(null);
            canvas.setBitmap(preview);
            canvas.drawColor(0, PorterDuff.Mode.CLEAR);
            canvas.drawBitmap(thickInnerBlur, thickInnerBlurOffset[0], thickInnerBlurOffset[1],
                    paint);
            canvas.drawBitmap(thickOuterBlur, outerBlurOffset[0], outerBlurOffset[1], paint);

            // draw the bright outline
            canvas.drawBitmap(brightOutline, brightOutlineOffset[0], brightOutlineOffset[1], paint);

            // cleanup
            canvas.setBitmap(null);
            brightOutline.recycle();
            thickOuterBlur.recycle();
            thickInnerBlur.recycle();

            generatedDragOutline = preview;
        }
    }
}