Function prepare

src/renderers/createReferenceLineRenderer.ts:218–338

(gridArea, lines)

  };

  const prepare: ReferenceLineRenderer['prepare'] = (gridArea, lines) => {
    assertNotDisposed();

    if (!Array.isArray(lines)) {
      throw new Error('ReferenceLineRenderer.prepare: lines must be an array.');
    }
    if (!isFiniteGridArea(gridArea)) {
      throw new Error('ReferenceLineRenderer.prepare: gridArea dimensions must be finite numbers.');
    }
    if (gridArea.canvasWidth <= 0 || gridArea.canvasHeight <= 0) {
      throw new Error('ReferenceLineRenderer.prepare: canvas dimensions must be positive.');
    }
    if (gridArea.left < 0 || gridArea.right < 0 || gridArea.top < 0 || gridArea.bottom < 0) {
      throw new Error('ReferenceLineRenderer.prepare: gridArea margins must be non-negative.');
    }

    // Be resilient: older call sites may omit/incorrectly pass DPR. Defaulting avoids hard crashes.
    const dpr =
      Number.isFinite(gridArea.devicePixelRatio) && gridArea.devicePixelRatio > 0 ? gridArea.devicePixelRatio : 1;

    const plotLeftDevice = gridArea.left * dpr;
    const plotTopDevice = gridArea.top * dpr;
    const plotRightDevice = gridArea.canvasWidth - gridArea.right * dpr;
    const plotBottomDevice = gridArea.canvasHeight - gridArea.bottom * dpr;
    const plotWidthDevice = plotRightDevice - plotLeftDevice;
    const plotHeightDevice = plotBottomDevice - plotTopDevice;

    if (!(plotWidthDevice > 0) || !(plotHeightDevice > 0)) {
      instanceCount = 0;
      return;
    }

    // Write uniforms.
    const uniforms = new Float32Array(8);
    uniforms[0] = gridArea.canvasWidth;
    uniforms[1] = gridArea.canvasHeight;
    uniforms[2] = plotLeftDevice;
    uniforms[3] = plotTopDevice;
    uniforms[4] = plotWidthDevice;
    uniforms[5] = plotHeightDevice;
    uniforms[6] = dpr;
    uniforms[7] = 0;
    writeUniformBuffer(device, vsUniformBuffer, uniforms);

    // Early out: no instances.
    if (lines.length === 0) {
      instanceCount = 0;
      return;
    }

    // Ensure instance buffer capacity.
    if (!instanceBuffer || instanceCapacity < lines.length) {
      const nextCapacity = Math.max(1, Math.ceil(lines.length * 1.5));
      const size = Math.max(4, nextCapacity * INSTANCE_STRIDE_BYTES);

      if (instanceBuffer) {
        try {
          instanceBuffer.destroy();