dist/famous-flex.js
function _layout(size, scrollOffset, nested) {

        // Track the number of times the layout-function was executed
        this._debug.layoutCount++;
        //_log.call(this, 'Layout, scrollOffset: ', scrollOffset, ', particle: ', this._scroll.particle.getPosition1D());

        // Determine start & end
        var scrollStart = 0 - Math.max(this.options.extraBoundsSpace[0], 1);
        var scrollEnd = size[this._direction] + Math.max(this.options.extraBoundsSpace[1], 1);
        if (this.options.paginated && (this.options.paginationMode === PaginationMode.PAGE)) {
            scrollStart = scrollOffset - this.options.extraBoundsSpace[0];
            scrollEnd = scrollOffset + size[this._direction] + this.options.extraBoundsSpace[1];
            if ((scrollOffset + size[this._direction]) < 0) {
                scrollStart += size[this._direction];
                scrollEnd += size[this._direction];
            }
            else if ((scrollOffset - size[this._direction]) > 0) {
                scrollStart -= size[this._direction];
                scrollEnd -= size[this._direction];
            }
        }
        if (this.options.layoutAll) {
            scrollStart = -1000000;
            scrollEnd = 1000000;
        }

        // Prepare for layout
        var layoutContext = this._nodes.prepareForLayout(
            this._viewSequence,     // first node to layout
            this._nodesById, {      // so we can do fast id lookups
                size: size,
                direction: this._direction,
                reverse: this.options.alignment ? true : false,
                scrollOffset: this.options.alignment ? (scrollOffset + size[this._direction]) : scrollOffset,
                scrollStart: scrollStart,
                scrollEnd: scrollEnd
            }
        );

        // Layout objects
        if (this._layout._function) {
            this._layout._function(
                layoutContext,          // context which the layout-function can use
                this._layout.options    // additional layout-options
            );
        }
        this._scroll.unnormalizedScrollOffset = scrollOffset;

        // Call post-layout function
        if (this._postLayout) {
            this._postLayout(size, scrollOffset);
        }

        // Mark non-invalidated nodes for removal
        this._nodes.removeNonInvalidatedNodes(this.options.flowOptions.removeSpec);

        // Check whether the bounds have been reached
        //var oldBoundsReached = this._scroll.boundsReached;
        _calcBounds.call(this, size, scrollOffset);
        //if (oldBoundsReached !== this._scroll.boundsReached) {
        //    _log.call(this, 'bounds reached changed (', oldBoundsReached, ' != ', this._scroll.boundsReached, ')');
        //}

        // Update scroll-to spring
        _calcScrollToOffset.call(this, size, scrollOffset);

        // When pagination is enabled, snap to page
        _snapToPage.call(this);

        // If the bounds have changed, and the scroll-offset would be different
        // than before, then re-layout entirely using the new offset.
        var newScrollOffset = _calcScrollOffset.call(this, true);
        if (!nested && (newScrollOffset !== scrollOffset)) {
            //_log.call(this, 'offset changed, re-layouting... (', scrollOffset, ' != ', newScrollOffset, ')');
            return _layout.call(this, size, newScrollOffset, true);
        }

        // Normalize scroll offset so that the current viewsequence node is as close to the
        // top as possible and the layout function will need to process the least amount
        // of renderables.
        scrollOffset = _normalizeViewSequence.call(this, size, scrollOffset);

        // Update spring
        _updateSpring.call(this);

        // Cleanup any nodes in case of a VirtualViewSequence
        this._nodes.removeVirtualViewSequenceNodes();

        // Calculate scroll-length and use that as the true-size (height)
        if (this.options.size && (this.options.size[this._direction] === true)) {
            var scrollLength = 0;
            var node = this._nodes.getStartEnumNode();
            while (node) {
                if (node._invalidated && node.scrollLength) {
                    scrollLength += node.scrollLength;
                }
                node = node._next;
            }
            this._size = this._size || [0, 0];
            this._size[0] = this.options.size[0];
            this._size[1] = this.options.size[1];
            this._size[this._direction] = scrollLength;
        }

        return scrollOffset;
    }
function _layout(size, scrollOffset, nested) {

        // Track the number of times the layout-function was executed
        this._debug.layoutCount++;
        //_log.call(this, 'Layout, scrollOffset: ', scrollOffset, ', particle: ', this._scroll.particle.getPosition1D());

        // Determine start & end
        var scrollStart = 0 - Math.max(this.options.extraBoundsSpace[0], 1);
        var scrollEnd = size[this._direction] + Math.max(this.options.extraBoundsSpace[1], 1);
        if (this.options.paginated && (this.options.paginationMode === PaginationMode.PAGE)) {
            scrollStart = scrollOffset - this.options.extraBoundsSpace[0];
            scrollEnd = scrollOffset + size[this._direction] + this.options.extraBoundsSpace[1];
            if ((scrollOffset + size[this._direction]) < 0) {
                scrollStart += size[this._direction];
                scrollEnd += size[this._direction];
            }
            else if ((scrollOffset - size[this._direction]) > 0) {
                scrollStart -= size[this._direction];
                scrollEnd -= size[this._direction];
            }
        }
        if (this.options.layoutAll) {
            scrollStart = -1000000;
            scrollEnd = 1000000;
        }

        // Prepare for layout
        var layoutContext = this._nodes.prepareForLayout(
            this._viewSequence,     // first node to layout
            this._nodesById, {      // so we can do fast id lookups
                size: size,
                direction: this._direction,
                reverse: this.options.alignment ? true : false,
                scrollOffset: this.options.alignment ? (scrollOffset + size[this._direction]) : scrollOffset,
                scrollStart: scrollStart,
                scrollEnd: scrollEnd
            }
        );

        // Layout objects
        if (this._layout._function) {
            this._layout._function(
                layoutContext,          // context which the layout-function can use
                this._layout.options    // additional layout-options
            );
        }
        this._scroll.unnormalizedScrollOffset = scrollOffset;

        // Call post-layout function
        if (this._postLayout) {
            this._postLayout(size, scrollOffset);
        }

        // Mark non-invalidated nodes for removal
        this._nodes.removeNonInvalidatedNodes(this.options.flowOptions.removeSpec);

        // Check whether the bounds have been reached
        //var oldBoundsReached = this._scroll.boundsReached;
        _calcBounds.call(this, size, scrollOffset);
        //if (oldBoundsReached !== this._scroll.boundsReached) {
        //    _log.call(this, 'bounds reached changed (', oldBoundsReached, ' != ', this._scroll.boundsReached, ')');
        //}

        // Update scroll-to spring
        _calcScrollToOffset.call(this, size, scrollOffset);

        // When pagination is enabled, snap to page
        _snapToPage.call(this);

        // If the bounds have changed, and the scroll-offset would be different
        // than before, then re-layout entirely using the new offset.
        var newScrollOffset = _calcScrollOffset.call(this, true);
        if (!nested && (newScrollOffset !== scrollOffset)) {
            //_log.call(this, 'offset changed, re-layouting... (', scrollOffset, ' != ', newScrollOffset, ')');
            return _layout.call(this, size, newScrollOffset, true);
        }

        // Normalize scroll offset so that the current viewsequence node is as close to the
        // top as possible and the layout function will need to process the least amount
        // of renderables.
        scrollOffset = _normalizeViewSequence.call(this, size, scrollOffset);

        // Update spring
        _updateSpring.call(this);

        // Cleanup any nodes in case of a VirtualViewSequence
        this._nodes.removeVirtualViewSequenceNodes();

        // Calculate scroll-length and use that as the true-size (height)
        if (this.options.size && (this.options.size[this._direction] === true)) {
            var scrollLength = 0;
            var node = this._nodes.getStartEnumNode();
            while (node) {
                if (node._invalidated && node.scrollLength) {
                    scrollLength += node.scrollLength;
                }
                node = node._next;
            }
            this._size = this._size || [0, 0];
            this._size[0] = this.options.size[0];
            this._size[1] = this.options.size[1];
            this._size[this._direction] = scrollLength;
        }

        return scrollOffset;
    }
Executes the layout and updates the state of the scrollview.