Method syncHidden

deps/v8/tools/turbolizer/src/views/range-view.ts:1834–1881

()

  // This function is used to hide the rows which are not currently in view and
  // so reduce the performance cost of things like hit tests and scrolling.
  public syncHidden(): void {
    const isFlipped = this.view.userSettings.get("flipped");
    const toHide = new Array<[HTMLElement, HTMLElement]>();

    const sampleCell = this.view.divs.registers.children[1] as HTMLElement;
    const buffer = 2 * (isFlipped ? sampleCell.clientWidth : sampleCell.clientHeight);
    const min = (isFlipped ? this.view.divs.grid.offsetLeft + this.view.divs.grid.scrollLeft
                           : this.view.divs.grid.offsetTop + this.view.divs.grid.scrollTop)
                - buffer;
    const max = (isFlipped ? min + this.view.divs.grid.clientWidth
                           : min + this.view.divs.grid.clientHeight)
                + buffer;

    // The rows are grouped by being contained within a group div. This is so as to allow
    // groups of rows to easily be displayed and hidden with less of a performance cost.
    // Each row in the mainGroup div is matched with an equivalent placeholder row in
    // the placeholderGroup div that will be shown when mainGroup is hidden so as to maintain
    // the dimensions and scroll positions of the grid.

    const rangeGroups = this.view.divs.grid.children;
    for (let i = 1; i < rangeGroups.length; i += 2) {
      const mainGroup = rangeGroups[i] as HTMLElement;
      const placeholderGroup = rangeGroups[i - 1] as HTMLElement;
      const isHidden = mainGroup.classList.contains("range-hidden");
      // The offsets are used to calculate whether the group is in view.
      const offsetMin = this.getOffset(mainGroup.firstChild as HTMLElement,
        placeholderGroup.firstChild as HTMLElement, isHidden, isFlipped);
      const offsetMax = this.getOffset(mainGroup.lastChild as HTMLElement,
        placeholderGroup.lastChild as HTMLElement, isHidden, isFlipped);

      if (offsetMax > min && offsetMin < max) {
        if (isHidden) {
          // Show the rows, hide the placeholders.
          mainGroup.classList.toggle("range-hidden", false);
          placeholderGroup.classList.toggle("range-hidden", true);
        }
      } else if (!isHidden) {
        // Only hide the rows once the new rows are shown so that scrollLeft is not lost.
        toHide.push([mainGroup, placeholderGroup]);
      }
    }

    for (const [mainGroup, placeholderGroup] of toHide) {
      // Hide the rows, show the placeholders.
      mainGroup.classList.toggle("range-hidden", true);
      placeholderGroup.classList.toggle("range-hidden", false);
    }
  }

  // This function is required to keep the axes labels in line with the grid
  // content when scrolling.