getWhitespaceViewportData(verticalOffset1, verticalOffset2) {
        this._checkPendingChanges();
        verticalOffset1 = verticalOffset1 | 0;
        verticalOffset2 = verticalOffset2 | 0;
        const startIndex = this.getWhitespaceIndexAtOrAfterVerticallOffset(verticalOffset1);
        const endIndex = this.getWhitespacesCount() - 1;
        if (startIndex < 0) {
            return [];
        }
        const result = [];
        for (let i = startIndex; i <= endIndex; i++) {
            const top = this.getVerticalOffsetForWhitespaceIndex(i);
            const height = this.getHeightForWhitespaceIndex(i);
            if (top >= verticalOffset2) {
                break;
            }
            result.push({
                id: this.getIdForWhitespaceIndex(i),
                afterLineNumber: this.getAfterLineNumberForWhitespaceIndex(i),
                verticalOffset: top,
                height: height
            });
        }
        return result;
    }
Get a list of whitespaces that are positioned between `verticalOffset1` and `verticalOffset2`.

@param verticalOffset1 The beginning of the viewport.
@param verticalOffset2 The end of the viewport.
@return An array with all the whitespaces in the viewport. If no whitespace is in viewport, the array is empty.