src/vs/workbench/contrib/search/common/searchModel.ts/Match/preview
class Match:	preview(): { before: string; inside: string; after: string; } {
		let before = this._oneLinePreviewText.substring(0, this._rangeInPreviewText.startColumn - 1),
			inside = this.getMatchString(),
			after = this._oneLinePreviewText.substring(this._rangeInPreviewText.endColumn - 1);

		before = lcut(before, 26);
		before = before.trimLeft();

		let charsRemaining = Match.MAX_PREVIEW_CHARS - before.length;
		inside = inside.substr(0, charsRemaining);
		charsRemaining -= inside.length;
		after = after.substr(0, charsRemaining);

		return {
			before,
			inside,
			after,
		};
	}