On Fri, Nov 1, 2013 at 12:51 PM, Armin Le Grand <armin.le.gr...@me.com> wrote: > Hi Rob, > > > On 01.11.2013 17:23, Rob Weir wrote: >> >> Yesterday I was create a diagram in Impress. It was a complicated >> diagram, around 20 small circles and squares, with a lot of connectors >> between them. I wasted a lot of time to make it look good, making the >> nodes so they did not overlap, getting the nodes arranged so the >> closely-connected ones were adjacent, optimizing the placement of the >> connectors, etc. It was a tedious manual process. >> >> I wish there was a button I could press in the toolbar called >> "optimize layout" that would do that all for me. >> >> This should be possible. Graph layout algorithms are well-known [1]. >> There are popular open source packages like graphviz that implement >> some of these algorithms. You define the nodes and the edges and >> graphviz determines an optimal layout. >> >> It should be possible to take an Impress (or Draw) diagram and extract >> the abstract qualities of the diagram (the nodes, and their >> connections), create an optimal layout using graphviz and then bring >> that layout back into the diagram and apply it. I know it could be >> done by directly operating on the ODF XML. I assume it could be done >> at runtime as well. > > > Nice idea, and surely useful, but connectors know only the two objects they > are connected with, thus there is no way for them to find out what 'other' > objects they should avoid to travel over. That would be a lot of 'guessing',
That's the point of a graph layout algorithm. All graphviz needs is a list of nodes and edges and it applies an algorithm to create an optimal layout. There are various algorithms. Some use physical analogies, treating the edges as idealized springs and use a simulation of the physical forces to determine the layout. Others apply simulated annealing with an objective function based on number of overlapping lines and similar aesthetic factors, > e.g. do you avoid objects on the masterpage, too? The rectangle shape the > whole structure is lying above? Who defines what the 'whole structure' is? When I do diagrams like this I do it on a blank page, with no masterpage objects. > Surely it can be done e.g. with an extension working on a selection of > objects; as input that selection would need something like the connectors > (how else to define the connecitons?), but potentially cannot use these for > output, simply because connectors are limited to 5 line segments currently > (the whole layouting is based on this, and - even worse - the possible > maximum thee control points to adjust the maximum three inner edges). > Thus, it may be possible by creating simple polygons as output instead of > the connectors, but else I doubt it could be done without core changes, > sorry > I'd do it as three stages: 1) Determine the ideal layout, based on just knowledge of the topology, i.e., the nodes and edges as points and lines. 2) Apply the ideal layout back to the original diagram. 3) Scale the nodes if needed to avoid overlap of nodes. (Or allow the user to tweak the diagram manually) It is worth reviewing the example graphviz layouts. It works rather well: http://www.graphviz.org/Gallery.php -Rob > Sincerely, > Armin > >> >> Something to think about. >> >> [1] http://en.wikipedia.org/wiki/Graph_drawing >> >> [2] http://www.graphviz.org/ >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@openoffice.apache.org >> For additional commands, e-mail: dev-h...@openoffice.apache.org >> > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@openoffice.apache.org > For additional commands, e-mail: dev-h...@openoffice.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@openoffice.apache.org For additional commands, e-mail: dev-h...@openoffice.apache.org
