src/vs/editor/browser/viewParts/marginDecorations/marginDecorations.ts/MarginViewLineDecorationsOverlay/prepareRender
class MarginViewLineDecorationsOverlay:	public prepareRender(ctx: RenderingContext): void {
		const visibleStartLineNumber = ctx.visibleRange.startLineNumber;
		const visibleEndLineNumber = ctx.visibleRange.endLineNumber;
		const toRender = this._render(visibleStartLineNumber, visibleEndLineNumber, this._getDecorations(ctx));

		const output: string[] = [];
		for (let lineNumber = visibleStartLineNumber; lineNumber <= visibleEndLineNumber; lineNumber++) {
			const lineIndex = lineNumber - visibleStartLineNumber;
			const classNames = toRender[lineIndex];
			let lineOutput = '';
			for (let i = 0, len = classNames.length; i < len; i++) {
				lineOutput += '<div class="cmdr ' + classNames[i] + '" style=""></div>';
			}
			output[lineIndex] = lineOutput;
		}

		this._renderResult = output;
	}