src/vs/editor/browser/viewParts/overviewRuler/overviewRuler.ts/OverviewRuler/_renderOneLane
class OverviewRuler:	private _renderOneLane(ctx: CanvasRenderingContext2D, colorZones: ColorZone[], id2Color: string[], width: number): void {

		let currentColorId = 0;
		let currentFrom = 0;
		let currentTo = 0;

		for (const zone of colorZones) {

			const zoneColorId = zone.colorId;
			const zoneFrom = zone.from;
			const zoneTo = zone.to;

			if (zoneColorId !== currentColorId) {
				ctx.fillRect(0, currentFrom, width, currentTo - currentFrom);

				currentColorId = zoneColorId;
				ctx.fillStyle = id2Color[currentColorId];
				currentFrom = zoneFrom;
				currentTo = zoneTo;
			} else {
				if (currentTo >= zoneFrom) {
					currentTo = Math.max(currentTo, zoneTo);
				} else {
					ctx.fillRect(0, currentFrom, width, currentTo - currentFrom);
					currentFrom = zoneFrom;
					currentTo = zoneTo;
				}
			}
		}

		ctx.fillRect(0, currentFrom, width, currentTo - currentFrom);

	}