NekoX/TMessagesProj/src/main/java/org/telegram/ui/Components/Paint/Input.java

package org.telegram.ui.Components.Paint;

import android.graphics.Matrix;
import android.view.MotionEvent;

import org.telegram.messenger.AndroidUtilities;

import java.util.Vector;

public class Input {

    private RenderView renderView;

    private boolean beganDrawing;
    private boolean isFirst;
    private boolean hasMoved;
    private boolean clearBuffer;

    private Point lastLocation;
    private double lastRemainder;

    private Point[] points = new Point[3];
    private int pointsCount;

    private Matrix invertMatrix;
    private float[] tempPoint = new float[2];

    public Input(RenderView render) {
        renderView = render;
    }

    public void setMatrix(Matrix m) {
        invertMatrix = new Matrix();
        m.invert(invertMatrix);
    }

    public void process(MotionEvent event, float scale) {
        int action = event.getActionMasked();
        float x = event.getX();
        float y = renderView.getHeight() - event.getY();

        tempPoint[0] = x;
        tempPoint[1] = y;
        invertMatrix.mapPoints(tempPoint);

        Point location = new Point(tempPoint[0], tempPoint[1], 1.0f);

        switch (action) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE: {
                if (!beganDrawing) {
                    beganDrawing = true;
                    hasMoved = false;
                    isFirst = true;

                    lastLocation = location;

                    points[0] = location;
                    pointsCount = 1;

                    clearBuffer = true;
                } else {
                    float distance = location.getDistanceTo(lastLocation);
                    if (distance < AndroidUtilities.dp(5.0f) / scale) {
                        return;
                    }

                    if (!hasMoved) {
                        renderView.onBeganDrawing();
                        hasMoved = true;
                    }

                    points[pointsCount] = location;
                    pointsCount++;

                    if (pointsCount == 3) {
                        smoothenAndPaintPoints(false);
                    }

                    lastLocation = location;
                }
                break;
            }
            case MotionEvent.ACTION_UP: {
                if (!hasMoved) {
                    if (renderView.shouldDraw()) {
                        location.edge = true;
                        paintPath(new Path(location));
                    }
                    reset();
                } else if (pointsCount > 0) {
                    smoothenAndPaintPoints(true);
                }

                pointsCount = 0;

                renderView.getPainting().commitStroke(renderView.getCurrentColor());
                beganDrawing = false;

                renderView.onFinishedDrawing(hasMoved);
                break;
            }
            case MotionEvent.ACTION_CANCEL: {
                renderView.getPainting().clearStroke();
                pointsCount = 0;
                beganDrawing = false;
                break;
            }
        }
    }

    private void reset() {
        pointsCount = 0;
    }

    private void smoothenAndPaintPoints(boolean ended) {
        if (pointsCount > 2) {
            Vector<Point> points = new Vector<>();

            Point prev2 = this.points[0];
            Point prev1 = this.points[1];
            Point cur = this.points[2];

            if (cur == null || prev1 == null || prev2 == null) {
                return;
            }

            Point midPoint1 = prev1.multiplySum(prev2, 0.5f);
            Point midPoint2 = cur.multiplySum(prev1, 0.5f);

            int segmentDistance = 1;
            float distance = midPoint1.getDistanceTo(midPoint2);
            int numberOfSegments = (int) Math.min(48, Math.max(Math.floor(distance / segmentDistance), 24));

            float t = 0.0f;
            float step = 1.0f / (float) numberOfSegments;

            for (int j = 0; j < numberOfSegments; j++) {
                Point point = smoothPoint(midPoint1, midPoint2, prev1, t);
                if (isFirst) {
                    point.edge = true;
                    isFirst = false;
                }
                points.add(point);
                t += step;
            }

            if (ended) {
                midPoint2.edge = true;
            }
            points.add(midPoint2);

            Point[] result = new Point[points.size()];
            points.toArray(result);

            Path path = new Path(result);
            paintPath(path);

            System.arraycopy(this.points, 1, this.points, 0, 2);

            if (ended) {
                pointsCount = 0;
            } else {
                pointsCount = 2;
            }
        } else {
            Point[] result = new Point[pointsCount];
            System.arraycopy(this.points, 0, result, 0, pointsCount);
            Path path = new Path(result);
            paintPath(path);
        }
    }

    private Point smoothPoint(Point midPoint1, Point midPoint2, Point prev1, float t) {
        double a1 = Math.pow(1.0f - t, 2);
        double a2 = (2.0f * (1.0f - t) * t);
        double a3 = t * t;

        return new Point(midPoint1.x * a1 + prev1.x * a2 + midPoint2.x * a3, midPoint1.y * a1 + prev1.y * a2 + midPoint2.y * a3, 1.0f);
    }

    private void paintPath(final Path path) {
        path.setup(renderView.getCurrentColor(), renderView.getCurrentWeight(), renderView.getCurrentBrush());

        if (clearBuffer) {
            lastRemainder = 0.0f;
        }

        path.remainder = lastRemainder;

        renderView.getPainting().paintStroke(path, clearBuffer, () -> AndroidUtilities.runOnUIThread(() -> lastRemainder = path.remainder));
        clearBuffer = false;
    }
}