src/vs/editor/common/viewLayout/viewLineRenderer.ts/CharacterMapping/charOffsetToPartData
class CharacterMapping:	private charOffsetToPartData(charOffset: number): number {
		if (this.length === 0) {
			return 0;
		}
		if (charOffset < 0) {
			return this._data[0];
		}
		if (charOffset >= this.length) {
			return this._data[this.length - 1];
		}
		return this._data[charOffset];
	}