Which language and framework are best for building a cross-platform 2D animation editor?

C++ is a common choice for software like this because it gives you strong performance and low-level control over rendering, memory, and GPU integration. That said, C# or another higher-level language can be a much friendlier way to prototype and build the editor. You may give up some control and potentially some performance, but a well-designed application can still be very capable. If profiling later shows that certain operations are too slow, those parts can often be optimized separately.

Python with Manim is useful for generating programmatic animations, especially mathematical or educational ones, but it probably isn’t the best foundation for a full drawing-focused editor with interactive brushes, layers, and a timeline. For this project, a desktop framework with strong GPU-backed canvas support would likely be a better starting point.

C# has worked well for projects in this general space. It’s easier to develop with than C++ and provides a large ecosystem for desktop UI, graphics, and file handling. The garbage collector usually isn’t a major issue for an animation editor if you avoid creating excessive temporary objects during rendering and keep the real-time drawing path carefully designed. It could be a practical choice for getting a usable version running quickly.

If cross-platform support is important, .NET paired with Avalonia is worth investigating. Avalonia can provide a native-feeling desktop UI across Windows and other platforms, while its rendering stack supports hardware acceleration. It may be a good fit for the editor interface, timelines, panels, and tools. You could also evaluate a game engine such as Godot or Unity if you want ready-made real-time 2D rendering, though you would still need to build much of the document, layer, brush, and editing architecture yourself.