Function prepare

src/renderers/createCrosshairRenderer.ts:317–351

(x, y, gridArea, renderOptions)

  };

  const prepare: CrosshairRenderer['prepare'] = (x, y, gridArea, renderOptions) => {
    assertNotDisposed();

    // Validate options up-front for deterministic behavior.
    if (typeof renderOptions.showX !== 'boolean' || typeof renderOptions.showY !== 'boolean') {
      throw new Error('CrosshairRenderer.prepare: showX/showY must be boolean.');
    }
    if (typeof renderOptions.color !== 'string') {
      throw new Error('CrosshairRenderer.prepare: color must be a string.');
    }
    if (!Number.isFinite(renderOptions.lineWidth) || renderOptions.lineWidth < 0) {
      throw new Error('CrosshairRenderer.prepare: lineWidth must be a finite non-negative number.');
    }

    const { vertices, scissor } = generateCrosshairVertices(x, y, gridArea, renderOptions);
    if (vertices.byteLength === 0) {
      vertexCount = 0;
    } else {
      stream.write(vertices);
      vertexCount = stream.getVertexCount();
    }

    // Identity transform (vertices are already in clip-space).
    writeUniformBuffer(device, vsUniformBuffer, createIdentityMat4Buffer());

    // Color.
    const rgba = parseCssColorToRgba01(renderOptions.color) ?? DEFAULT_CROSSHAIR_RGBA;
    const colorBuffer = new ArrayBuffer(4 * 4);
    new Float32Array(colorBuffer).set([rgba[0], rgba[1], rgba[2], rgba[3]]);
    writeUniformBuffer(device, fsUniformBuffer, colorBuffer);

    lastCanvasWidth = gridArea.canvasWidth;
    lastCanvasHeight = gridArea.canvasHeight;
    lastScissor = scissor;
  };

  const render: CrosshairRenderer['render'] = (passEncoder) => {
    assertNotDisposed();