Function prepare

src/renderers/createAnnotationMarkerRenderer.ts:167–247

({ canvasWidth, canvasHeight, devicePixelRatio, instances })

  };

  const prepare: AnnotationMarkerRenderer['prepare'] = ({ canvasWidth, canvasHeight, devicePixelRatio, instances }) => {
    assertNotDisposed();

    if (!Number.isFinite(canvasWidth) || !Number.isFinite(canvasHeight) || canvasWidth <= 0 || canvasHeight <= 0) {
      throw new Error('AnnotationMarkerRenderer.prepare: canvasWidth/canvasHeight must be positive finite numbers.');
    }
    if (!Array.isArray(instances)) {
      throw new Error('AnnotationMarkerRenderer.prepare: instances must be an array.');
    }

    writeVsUniforms(canvasWidth, canvasHeight, devicePixelRatio);

    ensureCpuInstanceCapacityFloats(instances.length * INSTANCE_STRIDE_FLOATS);
    const f32 = cpuInstanceStagingF32;
    let outFloats = 0;

    for (let i = 0; i < instances.length; i++) {
      const m = instances[i];
      if (!Number.isFinite(m.xCssPx) || !Number.isFinite(m.yCssPx)) continue;
      if (!Number.isFinite(m.sizeCssPx) || m.sizeCssPx <= 0) continue;

      const strokeWidthCss = m.strokeWidthCssPx ?? 0;
      const strokeRgba = m.strokeRgba ?? ([0, 0, 0, 0] as const);

      // Clamp colors to [0,1] for deterministic output.
      const fr = clamp01(m.fillRgba[0]);
      const fg = clamp01(m.fillRgba[1]);
      const fb = clamp01(m.fillRgba[2]);
      const fa = clamp01(m.fillRgba[3]);

      const sr = clamp01(strokeRgba[0]);
      const sg = clamp01(strokeRgba[1]);
      const sb = clamp01(strokeRgba[2]);
      const sa = clamp01(strokeRgba[3]);

      f32[outFloats + 0] = m.xCssPx;
      f32[outFloats + 1] = m.yCssPx;
      f32[outFloats + 2] = m.sizeCssPx;
      f32[outFloats + 3] = Number.isFinite(strokeWidthCss) ? Math.max(0, strokeWidthCss) : 0;

      f32[outFloats + 4] = fr;
      f32[outFloats + 5] = fg;
      f32[outFloats + 6] = fb;
      f32[outFloats + 7] = fa;

      f32[outFloats + 8] = sr;
      f32[outFloats + 9] = sg;
      f32[outFloats + 10] = sb;
      f32[outFloats + 11] = sa;

      outFloats += INSTANCE_STRIDE_FLOATS;
    }

    instanceCount = outFloats / INSTANCE_STRIDE_FLOATS;

    // PERFORMANCE: Early exit if no valid instances (skip buffer allocation/write)
    if (instanceCount === 0) {
      return;