src/vs/editor/browser/viewParts/currentLineHighlight/currentLineHighlight.ts/AbstractLineHighlightOverlay/prepareRender
class AbstractLineHighlightOverlay:	public prepareRender(ctx: RenderingContext): void {
		if (!this._shouldRenderThis()) {
			this._renderData = null;
			return;
		}
		const renderedLine = this._renderOne(ctx);
		const visibleStartLineNumber = ctx.visibleRange.startLineNumber;
		const visibleEndLineNumber = ctx.visibleRange.endLineNumber;
		const len = this._cursorLineNumbers.length;
		let index = 0;
		const renderData: string[] = [];
		for (let lineNumber = visibleStartLineNumber; lineNumber <= visibleEndLineNumber; lineNumber++) {
			const lineIndex = lineNumber - visibleStartLineNumber;
			while (index < len && this._cursorLineNumbers[index] < lineNumber) {
				index++;
			}
			if (index < len && this._cursorLineNumbers[index] === lineNumber) {
				renderData[lineIndex] = renderedLine;
			} else {
				renderData[lineIndex] = '';
			}
		}
		this._renderData = renderData;
	}