Function prepare

src/renderers/createHighlightRenderer.ts:108–165

(point, cssColor, sizeCssPx)

  };

  const prepare: HighlightRenderer['prepare'] = (point, cssColor, sizeCssPx) => {
    assertNotDisposed();

    if (!Number.isFinite(point.centerDeviceX) || !Number.isFinite(point.centerDeviceY)) {
      throw new Error('HighlightRenderer.prepare: point center must be finite.');
    }
    if (!Number.isFinite(point.canvasWidth) || !Number.isFinite(point.canvasHeight) || point.canvasWidth <= 0 || point.canvasHeight <= 0) {
      throw new Error('HighlightRenderer.prepare: canvasWidth/canvasHeight must be positive finite numbers.');
    }
    if (!isFiniteScissor(point.scissor)) {
      throw new Error('HighlightRenderer.prepare: scissor must be finite.');
    }
    if (!Number.isFinite(sizeCssPx) || sizeCssPx < 0) {
      throw new Error('HighlightRenderer.prepare: size must be a finite non-negative number.');
    }

    const dprRaw = point.devicePixelRatio;
    const dpr = Number.isFinite(dprRaw) && dprRaw > 0 ? dprRaw : 1;
    const baseRadiusDevicePx = sizeCssPx * dpr;

    // Slightly larger than the implied "normal" point size.
    const radius = Math.max(1, baseRadiusDevicePx * 1.5);
    const thickness = Math.max(1, Math.round(Math.max(2, radius * 0.25)));

    const seriesRgba = parseCssColorToRgba01(cssColor) ?? DEFAULT_RGBA;
    const ringRgba = brighten(seriesRgba, 1.25);
    const useDarkOutline = luminance(seriesRgba) > 0.7;
    const outlineRgba: readonly [number, number, number, number] = useDarkOutline ? [0, 0, 0, 0.9] : [1, 1, 1, 0.9];

    const buf = new ArrayBuffer(12 * 4);
    new Float32Array(buf).set([
      point.centerDeviceX,
      point.centerDeviceY,
      radius,
      thickness,
      ringRgba[0],
      ringRgba[1],
      ringRgba[2],
      1.0,
      outlineRgba[0],
      outlineRgba[1],
      outlineRgba[2],
      outlineRgba[3],
    ]);
    writeUniformBuffer(device, uniformBuffer, buf);

    lastCanvasWidth = point.canvasWidth;
    lastCanvasHeight = point.canvasHeight;

    // Clamp scissor to valid canvas bounds (defensive).
    const x0 = clampInt(Math.floor(point.scissor.x), 0, Math.max(0, point.canvasWidth));
    const y0 = clampInt(Math.floor(point.scissor.y), 0, Math.max(0, point.canvasHeight));
    const x1 = clampInt(Math.ceil(point.scissor.x + point.scissor.w), 0, Math.max(0, point.canvasWidth));
    const y1 = clampInt(Math.ceil(point.scissor.y + point.scissor.h), 0, Math.max(0, point.canvasHeight));
    lastScissor = { x: x0, y: y0, w: Math.max(0, x1 - x0), h: Math.max(0, y1 - y0) };

    hasPrepared = true;
  };