message: expose brush single displayable on specifed ctx.
diff: @@ -526,6 +526,10 @@ function setContextTransform(ctx: CanvasRenderingContext2D, el: Displayable) {
  const tmpRect = new BoundingRect(0, 0, 0, 0);
  const viewRect = new BoundingRect(0, 0, 0, 0);
  function isDisplayableCulled(el: Displayable, width: number, height: number) {
  + // Disable culling when width or height is 0
  + if (!width || !height) {
  + return false;
  + }
  tmpRect.copy(el.getBoundingRect());
  if (el.transform) {
  tmpRect.applyTransform(el.transform);
  @@ -640,6 +644,10 @@ function getStyle(el: Displayable, inHover?: boolean) {
  return inHover ? (el.__hoverStyle || el.style) : el.style;
  }
  +export function brushSingle(ctx: CanvasRenderingContext2D, el: Displayable) {
  + brush(ctx, el, { inHover: false, viewWidth: 0, viewHeight: 0 }, true);
  +}
  +
  // Brush different type of elements.
  export function brush(
  ctx: CanvasRenderingContext2D,
  