grafana/public/app/plugins/panel/candlestick/utils.ts

import { VizDisplayMode, ColorStrategy, CandleStyle } from './models.gen';
import uPlot from 'uplot';
import { colorManipulator } from '@grafana/data';

const { alpha } = colorManipulator;

export type FieldIndices = Record<string, number>;

interface RendererOpts {
  mode: VizDisplayMode;
  candleStyle: CandleStyle;
  fields: FieldIndices;
  colorStrategy: ColorStrategy;
  upColor: string;
  downColor: string;
  flatColor: string;
  volumeAlpha: number;
  flatAsUp: boolean;
}

export function drawMarkers(opts: RendererOpts) {
  let { mode, candleStyle, fields, colorStrategy, upColor, downColor, flatColor, volumeAlpha, flatAsUp = true } = opts;

  const drawPrice = mode !== VizDisplayMode.Volume && fields.high != null && fields.low != null;
  const asCandles = drawPrice && candleStyle === CandleStyle.Candles;
  const drawVolume = mode !== VizDisplayMode.Candles && fields.volume != null;

  function selectPath(priceDir: number, flatPath: Path2D, upPath: Path2D, downPath: Path2D, flatAsUp: boolean) {
    return priceDir > 0 ? upPath : priceDir < 0 ? downPath : flatAsUp ? upPath : flatPath;
  }

  let tIdx = 0,
    oIdx = fields.open,
    hIdx = fields.high,
    lIdx = fields.low,
    cIdx = fields.close,
    vIdx = fields.volume;

  return (u: uPlot) => {
    // split by discrete color to reduce draw calls
    let downPath, upPath, flatPath;
    // with adjusted reduced
    let downPathVol, upPathVol, flatPathVol;

    if (drawPrice) {
      flatPath = new Path2D();
      upPath = new Path2D();
      downPath = new Path2D();
    }

    if (drawVolume) {
      downPathVol = new Path2D();
      upPathVol = new Path2D();
      flatPathVol = new Path2D();
    }

    let hollowPath = new Path2D();

    let ctx = u.ctx;

    let tData = u.data[tIdx!];

    let oData = u.data[oIdx!];
    let cData = u.data[cIdx!];

    let hData = drawPrice ? u.data[hIdx!] : null;
    let lData = drawPrice ? u.data[lIdx!] : null;
    let vData = drawVolume ? u.data[vIdx!] : null;

    let zeroPx = vIdx != null ? Math.round(u.valToPos(0, u.series[vIdx!].scale!, true)) : null;

    let [idx0, idx1] = u.series[0].idxs!;

    let dataX = u.data[0];
    let dataY = oData;

    let colWidth = u.bbox.width;

    if (dataX.length > 1) {
      // prior index with non-undefined y data
      let prevIdx = null;

      // scan full dataset for smallest adjacent delta
      // will not work properly for non-linear x scales, since does not do expensive valToPosX calcs till end
      for (let i = 0, minDelta = Infinity; i < dataX.length; i++) {
        if (dataY[i] !== undefined) {
          if (prevIdx != null) {
            let delta = Math.abs(dataX[i] - dataX[prevIdx]);

            if (delta < minDelta) {
              minDelta = delta;
              colWidth = Math.abs(u.valToPos(dataX[i], 'x') - u.valToPos(dataX[prevIdx], 'x'));
            }
          }

          prevIdx = i;
        }
      }
    }

    let barWidth = Math.round(0.6 * colWidth);

    let stickWidth = 2;
    let outlineWidth = 2;

    if (barWidth <= 12) {
      stickWidth = outlineWidth = 1;
    }

    let halfWidth = Math.floor(barWidth / 2);

    for (let i = idx0; i <= idx1; i++) {
      let tPx = Math.round(u.valToPos(tData[i]!, 'x', true));

      // current close vs prior close
      let interDir = i === idx0 ? 0 : Math.sign(cData[i]! - cData[i - 1]!);
      // current close vs current open
      let intraDir = Math.sign(cData[i]! - oData[i]!);

      // volume
      if (drawVolume) {
        let outerPath = selectPath(
          colorStrategy === ColorStrategy.CloseClose ? interDir : intraDir,
          flatPathVol as Path2D,
          upPathVol as Path2D,
          downPathVol as Path2D,
          i === idx0 && ColorStrategy.CloseClose ? false : flatAsUp
        );

        let vPx = Math.round(u.valToPos(vData![i]!, u.series[vIdx!].scale!, true));
        outerPath.rect(tPx - halfWidth, vPx, barWidth, zeroPx! - vPx);
      }

      if (drawPrice) {
        let outerPath = selectPath(
          colorStrategy === ColorStrategy.CloseClose ? interDir : intraDir,
          flatPath as Path2D,
          upPath as Path2D,
          downPath as Path2D,
          i === idx0 && ColorStrategy.CloseClose ? false : flatAsUp
        );

        // stick
        let hPx = Math.round(u.valToPos(hData![i]!, u.series[hIdx!].scale!, true));
        let lPx = Math.round(u.valToPos(lData![i]!, u.series[lIdx!].scale!, true));
        outerPath.rect(tPx - Math.floor(stickWidth / 2), hPx, stickWidth, lPx - hPx);

        let oPx = Math.round(u.valToPos(oData[i]!, u.series[oIdx!].scale!, true));
        let cPx = Math.round(u.valToPos(cData[i]!, u.series[cIdx!].scale!, true));

        if (asCandles) {
          // rect
          let top = Math.min(oPx, cPx);
          let btm = Math.max(oPx, cPx);
          let hgt = Math.max(1, btm - top);
          outerPath.rect(tPx - halfWidth, top, barWidth, hgt);

          if (colorStrategy === ColorStrategy.CloseClose) {
            if (intraDir >= 0 && hgt > outlineWidth * 2) {
              hollowPath.rect(
                tPx - halfWidth + outlineWidth,
                top + outlineWidth,
                barWidth - outlineWidth * 2,
                hgt - outlineWidth * 2
              );
            }
          }
        } else {
          outerPath.rect(tPx - halfWidth, oPx, halfWidth, stickWidth);
          outerPath.rect(tPx, cPx, halfWidth, stickWidth);
        }
      }
    }

    ctx.save();

    ctx.rect(u.bbox.left, u.bbox.top, u.bbox.width, u.bbox.height);
    ctx.clip();

    if (drawVolume) {
      ctx.fillStyle = alpha(upColor, volumeAlpha);
      ctx.fill(upPathVol as Path2D);

      ctx.fillStyle = alpha(downColor, volumeAlpha);
      ctx.fill(downPathVol as Path2D);

      ctx.fillStyle = alpha(flatColor, volumeAlpha);
      ctx.fill(flatPathVol as Path2D);
    }

    if (drawPrice) {
      ctx.fillStyle = upColor;
      ctx.fill(upPath as Path2D);

      ctx.fillStyle = downColor;
      ctx.fill(downPath as Path2D);

      ctx.fillStyle = flatColor;
      ctx.fill(flatPath as Path2D);

      ctx.globalCompositeOperation = 'destination-out';
      ctx.fill(hollowPath);
    }

    ctx.restore();
  };
}