src/vs/editor/browser/viewParts/lines/viewLines.ts/ViewLines/_updateLineWidths
class ViewLines:	private _updateLineWidths(fast: boolean): boolean {
		const rendStartLineNumber = this._visibleLines.getStartLineNumber();
		const rendEndLineNumber = this._visibleLines.getEndLineNumber();

		let localMaxLineWidth = 1;
		let allWidthsComputed = true;
		for (let lineNumber = rendStartLineNumber; lineNumber <= rendEndLineNumber; lineNumber++) {
			const visibleLine = this._visibleLines.getVisibleLine(lineNumber);

			if (fast && !visibleLine.getWidthIsFast()) {
				// Cannot compute width in a fast way for this line
				allWidthsComputed = false;
				continue;
			}

			localMaxLineWidth = Math.max(localMaxLineWidth, visibleLine.getWidth());
		}

		if (allWidthsComputed && rendStartLineNumber === 1 && rendEndLineNumber === this._context.viewModel.getLineCount()) {
			// we know the max line width for all the lines
			this._maxLineWidth = 0;
		}

		this._ensureMaxLineWidth(localMaxLineWidth);

		return allWidthsComputed;
	}