FlexGanttFX Goes Open Source
Dirk Lemmerman has open sourced FlexGanttFX, a resource-scheduling framework for generating Gantt charts, after 15 years of development. The library is now available under the AGPL license, which will help address project maintenance and increase the code’s availability for use.
FlexGanttFX runs on JavaFX, enabling it to be used on desktops as well as mobile devices. The project includes runnable demos that demonstrate chart creation and rendering techniques.
Gantt Charts and Their Applications
Gantt charts represent the progress of multiple tasks over time, either parallel or sequential. They are commonly used in project or resource planning to understand how one thing impacts another, crossing industries like logistics, aviation, healthcare, as well as software project planning.
The framework operates high-performance charts by mixing Canvas rendering with standard FX nodes. This allows the application to render the chart itself as a single Canvas without re-applying the full effects for every element in the chart.
Key Features of FlexGanttFX
The framework is built on four primitives: rows, activities, layers, and links. Time is modeled with java.time.Instant throughout, and the timeline renders at any granularity from milliseconds to decades, with time zones, daylight-saving transitions, weekends, and working hours treated as part of the model rather than display settings.
Each row can carry its own layout: the standard layout draws classic bars, the chart layout renders activities as line or area charts so a capacity curve can sit beside the bars it constrains, and the pool layout packs overlapping activities into stacked lines. Editing is direct manipulation, with constraint hooks so the application’s own rules decide which moves are allowed.
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In comparison to other open-source projects, FlexGanttFX‘s selection of the AGPL license is similar to decisions made by other projects, such as iText, which also uses the AGPL license. This license contains a clause about modified versions of the software being used over a network, which may impact how companies use and modify the library.
They use this license to ensure that modifications are shared publicly.
Companies that modify the library must make their source code available to the public, even if they do not redistribute the modified version.
Larger vendors have made similar decisions, such as Elastic‘s return to open source and Grafana‘s 2021 license change. Other vendors like MongoDB selected AGPL before migrating away in 2018.
The AGPL license used by FlexGanttFX is a key aspect of its open-source release, and its implications will be interesting to watch as the project evolves.
It is now available for use.
