Method displayIfNeeded

packages/react-devtools-timeline/src/view-base/View.js:193–223

* Executes the display flow if this view needs to be drawn. * * 1. Lays out subviews with `layoutSubviews`. * 2. Draws content with `draw`.

(context: CanvasRenderingContext2D, viewRefs: ViewRefs)

   * 2. Draws content with `draw`.
   */
  displayIfNeeded(context: CanvasRenderingContext2D, viewRefs: ViewRefs) {
    if (
      (this._needsDisplay || this._subviewsNeedDisplay) &&
      rectIntersectsRect(this.frame, this.visibleArea) &&
      !sizeIsEmpty(this.visibleArea.size)
    ) {
      this.layoutSubviews();
      if (this._needsDisplay) {
        this._needsDisplay = false;
      }
      if (this._subviewsNeedDisplay) this._subviewsNeedDisplay = false;

      // Clip anything drawn by the view to prevent it from overflowing its visible area.
      const visibleArea = this.visibleArea;
      const region = new Path2D();
      region.rect(
        visibleArea.origin.x,
        visibleArea.origin.y,
        visibleArea.size.width,
        visibleArea.size.height,
      );
      context.save();
      context.clip(region);
      context.beginPath();

      this.draw(context, viewRefs);

      // Stop clipping
      context.restore();
    }
  }

  /**
   * Layout self and subviews.