We are happy to announce an initial version of GT Diagrammer, an engine for constructing diagrams interactively. This is the newest addition to the next generation GT built on Bloc.
It looks like this:
One requirement we had from the beginning was to make it work with any Bloc element. This means that the editing part had to be reasonably generic. To this end, we now have elements that can define visual editors. This is somewhat a combination between Magritte descriptions, and inspector extensions. An interesting side effect is that now we can edit visual properties when inspecting any element. In other words, we got the basic infrastructure of a UI painter. It looks like this:
The user interface essentially relies on two widgets: scrollable list and toggle button. While the visual look of the toggle button is inspired from material design, the most interesting part is that now we have an implementation for controlling looks per element instance. A key issue here is that looks can react to events coming from the element and inject visual attributes and possible even change behavior (for example, changing an icon while pressing a button). We will post more about looks soon.
We now also have a nice solution for overlays. For example, we have an overlay showing selection and an overlay for resizing elements.
Perhaps less obvious, Diagrammer also offers a basic infrastructure for the area of visual languages. As Diagrammer works with any Bloc elements, we can simply create dedicated visual elements. As an example, Diagrammer comes with an implementation of a UML class figure. Furthermore, as the functionality does not impose a specific model, custom language semantics can be mapped on visual actions.
There are several things to do still for it to become a mature solution. An important next step is to serialize a diagram scene in a reproducible manner. Currently, the diagram (or any element) can be exported as pdf (https://twitter.com/feenkcom/status/976580153802358786), svg (https://twitter.com/feenkcom/status/976578060429484032), png, gif or jpeg by directly using the low level canvas. However, for the diagram to be truly useful we need to store the result in either code or another reloadable form such as STON. Other future directions are related to figure controlling (for example, custom anchors or line bending points) and to enhanced editors.
To play with it, the easiest way is to download the new GT in a Pharo 6.1 image:
And then inspect:
The feenk team