Presentation Layout

I’m working on a set of presentation capabilities inspired by MIT’s Exhibit widget set. A lot of the data management core is identical, but I’m trying to play around with the presentation and interaction a bit more. My goal is to have something sufficiently flexible that I can implement a simple game with it.

The standard Exhibit practice if you have multiple views into a data set is to show the views with what is essentially a tabbed interface. You can select which view you want, but you usually don’t get both at the same time.

I’m working on a second way of doing presentations of multiple views: an arranged set of views in a layer. Additional views might be done as windows above the layer, but the primary working set of views will be in a layer.

I could make a system in which the author would have to lay out each view by hand specifying heights and widths and placements on a grid, but that strikes me as being too close to the typesetting and too far from the idea. I want the author to specify a general idea of what they want and then have the system do a reasonably good job of presenting that idea.

What I’m playing with at the moment is a system by which the author specifies how many units they want the presentation to have for height and width. This is an arbitrary number that is used to scale other measurements so they fit in the display space. This lets the system work with computer displays, printed pages, or other devices that might not work in pixels or have the same pixel density.

Then, for each widget in the layout, the author specifies the stretchability and compressibility of bits of glue that tie the widget to other widgets and the frame. Glue is also used to specify the sizing of the inside part of the widget. The system can work with the glues to find a reasonable set of heights, widths, and distances to make everything reasonably visible. This models a bit of how (La)TeX manages text on a page.

The benefit of this system is that users can not only resize elements if they need to and everything will respond, but they can add new widgets in the layout and everything will automatically reshuffle to accomodate the new widget.

I’m still working on a simple implementation that will let me test this. I think it’s a reasonable first pass at the problem. I know I’m using the word ‘reasonable’ a lot, but I’m not going for perfect. I’m going for something that is good enough, at least for now.

My initial algorithm will try to lay out the widgets as points on a frame using the glue relationships to determine relative ordering. Once laid out, I’ll use the tensions in the glue to correct the centers. Then, I can do some slight adjustments to get the widget frames in place. It isn’t quite as simple as taking the distance between centers: the tension is between edges, so we take vertical or horizontal distance, but not diagonal distance.