Merge "DO NOT MERGE Improved anti-aliasing for circular display mask" into cw-f-dev

import static com.android.server.wm.WindowManagerDebugConfig.TAG_WITH_CLASS_NAME;

import static com.android.server.wm.WindowManagerDebugConfig.TAG_WM;

import android.graphics.Bitmap;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

        mSurfaceControl = ctrl;

        mDrawNeeded = true;

        mPaint = new Paint();

        mPaint.setAntiAlias(true);

        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));

        mScreenOffset = screenOffset;

        mMaskThickness = maskThickness;

    }

    static private double distanceFromCenterSquared(double x, double y) {

        return x*x + y*y;

    }

    static private double distanceFromCenter(double x, double y) {

        return Math.sqrt(distanceFromCenterSquared(x, y));

    }

    static private double verticalLineIntersectsCircle(double x, double radius) {

        return Math.sqrt(radius*radius - x*x);

    }

    static private double  horizontalLineIntersectsCircle(double y, double radius) {

        return Math.sqrt(radius*radius - y*y);

    }

    static private double triangleArea(double width, double height) {

        return width * height / 2.0;

    }

    static private double trapezoidArea(double width, double height1, double height2) {

        return width * (height1 + height2) / 2.0;

    }

    static private double areaUnderChord(double radius, double chordLength) {

        double isocelesHeight = Math.sqrt(radius*radius - chordLength * chordLength / 4.0);

        double areaUnderIsoceles = isocelesHeight * chordLength / 2.0;

        double halfAngle = Math.asin(chordLength / (2.0 * radius));

        double areaUnderArc = halfAngle * radius * radius;

        return areaUnderArc - triangleArea(chordLength, isocelesHeight);

    }

    // Returns the fraction of the pixel at (px, py) covered by

    // the circle with center (cx, cy) and radius 'radius'

    static private double calcPixelShading(double cx, double cy, double px,

            double py, double radius) {

        // Translate so the center is at the origin

        px -= cx;

        py -= cy;

        // Reflect across the axis so the point is in the first quadrant

        px = Math.abs(px);

        py = Math.abs(py);

        // One more transformation which simplifies the logic later

        if (py > px) {

            double temp;

            temp = px;

            px = py;

            py = temp;

        }

        double left = px - 0.5;

        double right = px + 0.5;

        double bottom = py - 0.5;

        double top = py + 0.5;

        if (distanceFromCenterSquared(left, bottom) > radius*radius) {

            return 0.0;

        }

        if (distanceFromCenterSquared(right, top) < radius*radius) {

            return 1.0;

        }

        // Check if only the bottom-left corner of the pixel is inside the circle

        if (distanceFromCenterSquared(left, top) > radius*radius) {

            double triangleWidth = horizontalLineIntersectsCircle(bottom, radius) - left;

            double triangleHeight = verticalLineIntersectsCircle(left, radius) - bottom;

            double chordLength = distanceFromCenter(triangleWidth, triangleHeight);

            return triangleArea(triangleWidth, triangleHeight)

                   + areaUnderChord(radius, chordLength);

        }

        // Check if only the top-right corner of the pixel is outside the circle

        if (distanceFromCenterSquared(right, bottom) < radius*radius) {

            double triangleWidth = right - horizontalLineIntersectsCircle(top, radius);

            double triangleHeight = top - verticalLineIntersectsCircle(right, radius);

            double chordLength = distanceFromCenter(triangleWidth, triangleHeight);

            return 1 - triangleArea(triangleWidth, triangleHeight)

                   + areaUnderChord(radius, chordLength);

        }

        // It must be that the top-left and bottom-left corners are inside the circle

        double trapezoidWidth1 = horizontalLineIntersectsCircle(top, radius) - left;

        double trapezoidWidth2 = horizontalLineIntersectsCircle(bottom, radius) - left;

        double chordLength = distanceFromCenter(1, trapezoidWidth2 - trapezoidWidth1);

        double shading = trapezoidArea(1.0, trapezoidWidth1, trapezoidWidth2)

                         + areaUnderChord(radius, chordLength);

        // When top >= 0 and bottom <= 0 it's possible for the circle to intersect the pixel 4 times.

        // If so, remove the area of the section which crosses the right-hand edge.

        if (top >= 0 && bottom <= 0 && radius > right) {

            shading -= areaUnderChord(radius, 2 * verticalLineIntersectsCircle(right, radius));

        }

        return shading;

    }

    private void drawIfNeeded() {

        if (!mDrawNeeded || !mVisible || mDimensionsUnequal) {

            return;

            break;

        }

        int circleRadius = mScreenSize.x / 2;

        c.drawColor(Color.BLACK);

        // The radius is reduced by mMaskThickness to provide an anti aliasing effect on the display edges.

        c.drawCircle(circleRadius, circleRadius, circleRadius - mMaskThickness, mPaint);

        int maskWidth = mScreenSize.x - 2*mMaskThickness;

        int maskHeight;

        // Don't render the whole mask if it is partly offscreen.

        if (maskWidth > mScreenSize.y) {

            maskHeight = mScreenSize.y;

        } else {

            // To ensure the mask can be properly centered on the canvas the

            // bitmap dimensions must have the same parity as those of the canvas.

            maskHeight = mScreenSize.y - ((mScreenSize.y - maskWidth) & ~1);

        }

        double cx = (maskWidth - 1.0) / 2.0;

        double cy = (maskHeight - 1.0) / 2.0;

        double radius = maskWidth / 2.0;

        int[] pixels = new int[maskWidth * maskHeight];

        for (int py=0; py<maskHeight; py++) {

            for (int px=0; px<maskWidth; px++) {

                double shading = calcPixelShading(cx, cy, px, py, radius);

                pixels[maskWidth*py + px] =

                    Color.argb(255 - (int)Math.round(255.0*shading), 0, 0, 0);

            }

        }

        Bitmap transparency = Bitmap.createBitmap(pixels, maskWidth, maskHeight,

            Bitmap.Config.ARGB_8888);

        c.drawBitmap(transparency,

                     (float)mMaskThickness,

                     (float)((mScreenSize.y - maskHeight) / 2),

                     mPaint);

        mSurface.unlockCanvasAndPost(c);

    }