src/vs/editor/browser/controller/mouseTarget.ts/HitTestContext/getFullLineRangeAtCoord
class HitTestContext:	public getFullLineRangeAtCoord(mouseVerticalOffset: number): { range: EditorRange; isAfterLines: boolean } {
		if (this._context.viewLayout.isAfterLines(mouseVerticalOffset)) {
			// Below the last line
			const lineNumber = this._context.viewModel.getLineCount();
			const maxLineColumn = this._context.viewModel.getLineMaxColumn(lineNumber);
			return {
				range: new EditorRange(lineNumber, maxLineColumn, lineNumber, maxLineColumn),
				isAfterLines: true
			};
		}

		const lineNumber = this._context.viewLayout.getLineNumberAtVerticalOffset(mouseVerticalOffset);
		const maxLineColumn = this._context.viewModel.getLineMaxColumn(lineNumber);
		return {
			range: new EditorRange(lineNumber, 1, lineNumber, maxLineColumn),
			isAfterLines: false
		};
	}