Method resizeToFitContent

src/cdk/text-field/autosize.ts:297–336

* Resize the textarea to fit its content. * @param force Whether to force a height recalculation. By default the height will be * recalculated only if the value changed since the last call.

(force: boolean = false)

   *    recalculated only if the value changed since the last call.
   */
  resizeToFitContent(force: boolean = false) {
    // If autosizing is disabled, just skip everything else
    if (!this._enabled) {
      return;
    }

    this._cacheTextareaLineHeight();
    this._cacheTextareaPlaceholderHeight();

    // If we haven't determined the line-height yet, we know we're still hidden and there's no point
    // in checking the height of the textarea.
    if (!this._cachedLineHeight) {
      return;
    }

    const textarea = this._elementRef.nativeElement as HTMLTextAreaElement;
    const value = textarea.value;

    // Only resize if the value or minRows have changed since these calculations can be expensive.
    if (!force && this._minRows === this._previousMinRows && value === this._previousValue) {
      return;
    }

    const scrollHeight = this._measureScrollHeight();
    const height = Math.max(scrollHeight, this._cachedPlaceholderHeight || 0);

    // Use the scrollHeight to know how large the textarea *would* be if fit its entire value.
    textarea.style.height = `${height}px`;

    this._ngZone.runOutsideAngular(() => {
      if (typeof requestAnimationFrame !== 'undefined') {
        requestAnimationFrame(() => this._scrollToCaretPosition(textarea));
      } else {
        setTimeout(() => this._scrollToCaretPosition(textarea));
      }
    });

    this._previousValue = value;
    this._previousMinRows = this._minRows;
  }

  /**
   * Resets the textarea to its original size