html2canvas/src/render/bound-curves.ts

import {ElementContainer} from '../dom/element-container';
import {getAbsoluteValue, getAbsoluteValueForTuple} from '../css/types/length-percentage';
import {Vector} from './vector';
import {BezierCurve} from './bezier-curve';
import {Path} from './path';

export class BoundCurves {
    readonly topLeftBorderDoubleOuterBox: Path;
    readonly topRightBorderDoubleOuterBox: Path;
    readonly bottomRightBorderDoubleOuterBox: Path;
    readonly bottomLeftBorderDoubleOuterBox: Path;
    readonly topLeftBorderDoubleInnerBox: Path;
    readonly topRightBorderDoubleInnerBox: Path;
    readonly bottomRightBorderDoubleInnerBox: Path;
    readonly bottomLeftBorderDoubleInnerBox: Path;
    readonly topLeftBorderStroke: Path;
    readonly topRightBorderStroke: Path;
    readonly bottomRightBorderStroke: Path;
    readonly bottomLeftBorderStroke: Path;
    readonly topLeftBorderBox: Path;
    readonly topRightBorderBox: Path;
    readonly bottomRightBorderBox: Path;
    readonly bottomLeftBorderBox: Path;
    readonly topLeftPaddingBox: Path;
    readonly topRightPaddingBox: Path;
    readonly bottomRightPaddingBox: Path;
    readonly bottomLeftPaddingBox: Path;
    readonly topLeftContentBox: Path;
    readonly topRightContentBox: Path;
    readonly bottomRightContentBox: Path;
    readonly bottomLeftContentBox: Path;

    constructor(element: ElementContainer) {
        const styles = element.styles;
        const bounds = element.bounds;

        let [tlh, tlv] = getAbsoluteValueForTuple(styles.borderTopLeftRadius, bounds.width, bounds.height);
        let [trh, trv] = getAbsoluteValueForTuple(styles.borderTopRightRadius, bounds.width, bounds.height);
        let [brh, brv] = getAbsoluteValueForTuple(styles.borderBottomRightRadius, bounds.width, bounds.height);
        let [blh, blv] = getAbsoluteValueForTuple(styles.borderBottomLeftRadius, bounds.width, bounds.height);

        const factors = [];
        factors.push((tlh + trh) / bounds.width);
        factors.push((blh + brh) / bounds.width);
        factors.push((tlv + blv) / bounds.height);
        factors.push((trv + brv) / bounds.height);
        const maxFactor = Math.max(...factors);

        if (maxFactor > 1) {
            tlh /= maxFactor;
            tlv /= maxFactor;
            trh /= maxFactor;
            trv /= maxFactor;
            brh /= maxFactor;
            brv /= maxFactor;
            blh /= maxFactor;
            blv /= maxFactor;
        }

        const topWidth = bounds.width - trh;
        const rightHeight = bounds.height - brv;
        const bottomWidth = bounds.width - brh;
        const leftHeight = bounds.height - blv;

        const borderTopWidth = styles.borderTopWidth;
        const borderRightWidth = styles.borderRightWidth;
        const borderBottomWidth = styles.borderBottomWidth;
        const borderLeftWidth = styles.borderLeftWidth;

        const paddingTop = getAbsoluteValue(styles.paddingTop, element.bounds.width);
        const paddingRight = getAbsoluteValue(styles.paddingRight, element.bounds.width);
        const paddingBottom = getAbsoluteValue(styles.paddingBottom, element.bounds.width);
        const paddingLeft = getAbsoluteValue(styles.paddingLeft, element.bounds.width);

        this.topLeftBorderDoubleOuterBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth / 3,
                      bounds.top + borderTopWidth / 3,
                      tlh - borderLeftWidth / 3,
                      tlv - borderTopWidth / 3,
                      CORNER.TOP_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth / 3, bounds.top + borderTopWidth / 3);
        this.topRightBorderDoubleOuterBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + topWidth,
                      bounds.top + borderTopWidth / 3,
                      trh - borderRightWidth / 3,
                      trv - borderTopWidth / 3,
                      CORNER.TOP_RIGHT
                  )
                : new Vector(bounds.left + bounds.width - borderRightWidth / 3, bounds.top + borderTopWidth / 3);
        this.bottomRightBorderDoubleOuterBox =
            brh > 0 || brv > 0
                ? getCurvePoints(
                      bounds.left + bottomWidth,
                      bounds.top + rightHeight,
                      brh - borderRightWidth / 3,
                      brv - borderBottomWidth / 3,
                      CORNER.BOTTOM_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - borderRightWidth / 3,
                      bounds.top + bounds.height - borderBottomWidth / 3
                  );
        this.bottomLeftBorderDoubleOuterBox =
            blh > 0 || blv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth / 3,
                      bounds.top + leftHeight,
                      blh - borderLeftWidth / 3,
                      blv - borderBottomWidth / 3,
                      CORNER.BOTTOM_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth / 3, bounds.top + bounds.height - borderBottomWidth / 3);
        this.topLeftBorderDoubleInnerBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + (borderLeftWidth * 2) / 3,
                      bounds.top + (borderTopWidth * 2) / 3,
                      tlh - (borderLeftWidth * 2) / 3,
                      tlv - (borderTopWidth * 2) / 3,
                      CORNER.TOP_LEFT
                  )
                : new Vector(bounds.left + (borderLeftWidth * 2) / 3, bounds.top + (borderTopWidth * 2) / 3);
        this.topRightBorderDoubleInnerBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + topWidth,
                      bounds.top + (borderTopWidth * 2) / 3,
                      trh - (borderRightWidth * 2) / 3,
                      trv - (borderTopWidth * 2) / 3,
                      CORNER.TOP_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - (borderRightWidth * 2) / 3,
                      bounds.top + (borderTopWidth * 2) / 3
                  );
        this.bottomRightBorderDoubleInnerBox =
            brh > 0 || brv > 0
                ? getCurvePoints(
                      bounds.left + bottomWidth,
                      bounds.top + rightHeight,
                      brh - (borderRightWidth * 2) / 3,
                      brv - (borderBottomWidth * 2) / 3,
                      CORNER.BOTTOM_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - (borderRightWidth * 2) / 3,
                      bounds.top + bounds.height - (borderBottomWidth * 2) / 3
                  );
        this.bottomLeftBorderDoubleInnerBox =
            blh > 0 || blv > 0
                ? getCurvePoints(
                      bounds.left + (borderLeftWidth * 2) / 3,
                      bounds.top + leftHeight,
                      blh - (borderLeftWidth * 2) / 3,
                      blv - (borderBottomWidth * 2) / 3,
                      CORNER.BOTTOM_LEFT
                  )
                : new Vector(
                      bounds.left + (borderLeftWidth * 2) / 3,
                      bounds.top + bounds.height - (borderBottomWidth * 2) / 3
                  );
        this.topLeftBorderStroke =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth / 2,
                      bounds.top + borderTopWidth / 2,
                      tlh - borderLeftWidth / 2,
                      tlv - borderTopWidth / 2,
                      CORNER.TOP_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth / 2, bounds.top + borderTopWidth / 2);
        this.topRightBorderStroke =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + topWidth,
                      bounds.top + borderTopWidth / 2,
                      trh - borderRightWidth / 2,
                      trv - borderTopWidth / 2,
                      CORNER.TOP_RIGHT
                  )
                : new Vector(bounds.left + bounds.width - borderRightWidth / 2, bounds.top + borderTopWidth / 2);
        this.bottomRightBorderStroke =
            brh > 0 || brv > 0
                ? getCurvePoints(
                      bounds.left + bottomWidth,
                      bounds.top + rightHeight,
                      brh - borderRightWidth / 2,
                      brv - borderBottomWidth / 2,
                      CORNER.BOTTOM_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - borderRightWidth / 2,
                      bounds.top + bounds.height - borderBottomWidth / 2
                  );
        this.bottomLeftBorderStroke =
            blh > 0 || blv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth / 2,
                      bounds.top + leftHeight,
                      blh - borderLeftWidth / 2,
                      blv - borderBottomWidth / 2,
                      CORNER.BOTTOM_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth / 2, bounds.top + bounds.height - borderBottomWidth / 2);
        this.topLeftBorderBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(bounds.left, bounds.top, tlh, tlv, CORNER.TOP_LEFT)
                : new Vector(bounds.left, bounds.top);
        this.topRightBorderBox =
            trh > 0 || trv > 0
                ? getCurvePoints(bounds.left + topWidth, bounds.top, trh, trv, CORNER.TOP_RIGHT)
                : new Vector(bounds.left + bounds.width, bounds.top);
        this.bottomRightBorderBox =
            brh > 0 || brv > 0
                ? getCurvePoints(bounds.left + bottomWidth, bounds.top + rightHeight, brh, brv, CORNER.BOTTOM_RIGHT)
                : new Vector(bounds.left + bounds.width, bounds.top + bounds.height);
        this.bottomLeftBorderBox =
            blh > 0 || blv > 0
                ? getCurvePoints(bounds.left, bounds.top + leftHeight, blh, blv, CORNER.BOTTOM_LEFT)
                : new Vector(bounds.left, bounds.top + bounds.height);
        this.topLeftPaddingBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth,
                      bounds.top + borderTopWidth,
                      Math.max(0, tlh - borderLeftWidth),
                      Math.max(0, tlv - borderTopWidth),
                      CORNER.TOP_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth, bounds.top + borderTopWidth);
        this.topRightPaddingBox =
            trh > 0 || trv > 0
                ? getCurvePoints(
                      bounds.left + Math.min(topWidth, bounds.width - borderRightWidth),
                      bounds.top + borderTopWidth,
                      topWidth > bounds.width + borderRightWidth ? 0 : Math.max(0, trh - borderRightWidth),
                      Math.max(0, trv - borderTopWidth),
                      CORNER.TOP_RIGHT
                  )
                : new Vector(bounds.left + bounds.width - borderRightWidth, bounds.top + borderTopWidth);
        this.bottomRightPaddingBox =
            brh > 0 || brv > 0
                ? getCurvePoints(
                      bounds.left + Math.min(bottomWidth, bounds.width - borderLeftWidth),
                      bounds.top + Math.min(rightHeight, bounds.height - borderBottomWidth),
                      Math.max(0, brh - borderRightWidth),
                      Math.max(0, brv - borderBottomWidth),
                      CORNER.BOTTOM_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - borderRightWidth,
                      bounds.top + bounds.height - borderBottomWidth
                  );
        this.bottomLeftPaddingBox =
            blh > 0 || blv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth,
                      bounds.top + Math.min(leftHeight, bounds.height - borderBottomWidth),
                      Math.max(0, blh - borderLeftWidth),
                      Math.max(0, blv - borderBottomWidth),
                      CORNER.BOTTOM_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth, bounds.top + bounds.height - borderBottomWidth);
        this.topLeftContentBox =
            tlh > 0 || tlv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth + paddingLeft,
                      bounds.top + borderTopWidth + paddingTop,
                      Math.max(0, tlh - (borderLeftWidth + paddingLeft)),
                      Math.max(0, tlv - (borderTopWidth + paddingTop)),
                      CORNER.TOP_LEFT
                  )
                : new Vector(bounds.left + borderLeftWidth + paddingLeft, bounds.top + borderTopWidth + paddingTop);
        this.topRightContentBox =
            trh > 0 || trv > 0
                ? getCurvePoints(
                      bounds.left + Math.min(topWidth, bounds.width + borderLeftWidth + paddingLeft),
                      bounds.top + borderTopWidth + paddingTop,
                      topWidth > bounds.width + borderLeftWidth + paddingLeft ? 0 : trh - borderLeftWidth + paddingLeft,
                      trv - (borderTopWidth + paddingTop),
                      CORNER.TOP_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - (borderRightWidth + paddingRight),
                      bounds.top + borderTopWidth + paddingTop
                  );
        this.bottomRightContentBox =
            brh > 0 || brv > 0
                ? getCurvePoints(
                      bounds.left + Math.min(bottomWidth, bounds.width - (borderLeftWidth + paddingLeft)),
                      bounds.top + Math.min(rightHeight, bounds.height + borderTopWidth + paddingTop),
                      Math.max(0, brh - (borderRightWidth + paddingRight)),
                      brv - (borderBottomWidth + paddingBottom),
                      CORNER.BOTTOM_RIGHT
                  )
                : new Vector(
                      bounds.left + bounds.width - (borderRightWidth + paddingRight),
                      bounds.top + bounds.height - (borderBottomWidth + paddingBottom)
                  );
        this.bottomLeftContentBox =
            blh > 0 || blv > 0
                ? getCurvePoints(
                      bounds.left + borderLeftWidth + paddingLeft,
                      bounds.top + leftHeight,
                      Math.max(0, blh - (borderLeftWidth + paddingLeft)),
                      blv - (borderBottomWidth + paddingBottom),
                      CORNER.BOTTOM_LEFT
                  )
                : new Vector(
                      bounds.left + borderLeftWidth + paddingLeft,
                      bounds.top + bounds.height - (borderBottomWidth + paddingBottom)
                  );
    }
}

enum CORNER {
    TOP_LEFT = 0,
    TOP_RIGHT = 1,
    BOTTOM_RIGHT = 2,
    BOTTOM_LEFT = 3
}

const getCurvePoints = (x: number, y: number, r1: number, r2: number, position: CORNER): BezierCurve => {
    const kappa = 4 * ((Math.sqrt(2) - 1) / 3);
    const ox = r1 * kappa; // control point offset horizontal
    const oy = r2 * kappa; // control point offset vertical
    const xm = x + r1; // x-middle
    const ym = y + r2; // y-middle

    switch (position) {
        case CORNER.TOP_LEFT:
            return new BezierCurve(
                new Vector(x, ym),
                new Vector(x, ym - oy),
                new Vector(xm - ox, y),
                new Vector(xm, y)
            );
        case CORNER.TOP_RIGHT:
            return new BezierCurve(
                new Vector(x, y),
                new Vector(x + ox, y),
                new Vector(xm, ym - oy),
                new Vector(xm, ym)
            );
        case CORNER.BOTTOM_RIGHT:
            return new BezierCurve(
                new Vector(xm, y),
                new Vector(xm, y + oy),
                new Vector(x + ox, ym),
                new Vector(x, ym)
            );
        case CORNER.BOTTOM_LEFT:
        default:
            return new BezierCurve(
                new Vector(xm, ym),
                new Vector(xm - ox, ym),
                new Vector(x, y + oy),
                new Vector(x, y)
            );
    }
};

export const calculateBorderBoxPath = (curves: BoundCurves): Path[] => {
    return [curves.topLeftBorderBox, curves.topRightBorderBox, curves.bottomRightBorderBox, curves.bottomLeftBorderBox];
};

export const calculateContentBoxPath = (curves: BoundCurves): Path[] => {
    return [
        curves.topLeftContentBox,
        curves.topRightContentBox,
        curves.bottomRightContentBox,
        curves.bottomLeftContentBox
    ];
};

export const calculatePaddingBoxPath = (curves: BoundCurves): Path[] => {
    return [
        curves.topLeftPaddingBox,
        curves.topRightPaddingBox,
        curves.bottomRightPaddingBox,
        curves.bottomLeftPaddingBox
    ];
};