Graph layout algorithm

We are building a web-based flowchart diagram application, based on an underlying content structure that can be represented as a directed graph. The application involves the interactive creation of a flowchart diagram based on an underlying semantic content structure. We are using mxGraph as the graph diagramming/visualization library. The library provides an out-the-box implementation of a hierarchical layout algorithm, which provides the basis of what we need. However, we have a set of specific visual layout requirements and constraints that need to be incorporated into the algorithm. This will almost certainly require in-depth knowledge of graph layout theory. To give you an idea, some of these requirements are: * Sibling nodes appear in their natural order from left to right (and top down). A node should appear to the right and/or below a node that precedes it in the sequence. * Ability to switch from LTR to RTL orientation. * Nodes are horizontally aligned appropriately (e.g. a node is horizontally centered relative to its parent(s)) * Use node sequence metadata (that may override the natural node sequence) to determine the ordering of nodes in the graph. JavaScript experience will be a huge advantage, as the code is all in JavaScript. Please do not apply to this job if you do not have knowledge of graph layout theory. More detailed information will be provided on start of the project or if needed beforehand.