  Creating suitable diagrams for technical and scientific publications is
challenging and time-consuming, as manual control over the layout is required
to communicate information effectively. Existing diagramming tools usually
allow modeling the diagrams via a textual domain-specific language (DSL) that
can be rendered and auto-layouted or via a graphical editor. While auto-layout
is fast, the results are often not satisfying for most publications. However,
graphical editors are time-consuming to create large diagrams. The blended or
hybrid modeling concept enables creating diagrams efficiently using a DSL and
editing the rendered diagram via the graphical editor for fine-tuning. However,
hybrid modeling editors are limited to individual diagram types and do not save
the layout and style information in the textual description. Therefore, we
propose HyLiMo, a hybrid live-synchronized modular diagramming editor. In
HyLiMo, diagrams are created using an internal DSL and live synchronized with
an interactive graphical editor for the rendered diagram, allowing a
straightforward layout and style change, which is stored in the DSL code.
HyLiMo is independent of specific diagram types, but we offer specific
functionality for UML class diagrams. Using the language server protocol, we
implement it as a web app and IDE extension. The results of our user study
indicate that such an approach enables fast and precise diagramming.
