jphelan

    if len > MAX_FRAME_BYTES {
      return Err(format!(
        "requested frame buffer too large: {width}x{height} => {len} bytes"
      ));
    }

    // Deterministic per-frame fill color to help catch cross-talk in tests/debugging.
    let id = frame_id.0;
    let url_hash = match self.navigation.as_ref() {
      Some(IframeNavigation::Url(url)) => Self::url_hash(url),
      Some(IframeNavigation::AboutBlank) => Self::url_hash("about:blank"),
      Some(IframeNavigation::Srcdoc { content_hash }) => {
        let folded = (*content_hash as u32) ^ ((*content_hash >> 32) as u32);
        Self::url_hash("about:srcdoc") ^ folded
      }
      None => 0,
    };
    let r = (id as u8) ^ (url_hash as u8);
    let g = ((id >> 8) as u8) ^ ((url_hash >> 8) as u8);
    let b = ((id >> 16) as u8) ^ ((url_hash >> 16) as u8);
    let a = 0xFF;

    let mut rgba8 = vec![0u8; len];
    for px in rgba8.chunks_exact_mut(4) {
      px[0] = r;
      px[1] = g;
      px[2] = b;
      px[3] = a;
    }

    Ok(FrameBuffer {
      width,
      height,
      rgba8,
    })
  }