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setzer22 / egui_node_graph

Build your node graph applications in Rust, using egui
MIT License
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Zoom in/out supported by default (like in blackjack)? #53

Closed DerLando closed 2 years ago

DerLando commented 2 years ago

Hello, first of all thank you for extracting this amazing library from blackjack and making it available!

I was wondering if I might have missed the support for zooming in and out of the node graph, like possible in blackjack? I see panning being implemented by default by pressing middle mouse button and moving, but I don't see any handling for the scroll wheel in the code.

When changing the scroll value of the PanZoom struct manually, there does not seem to be any visual feedback of a change. Is zooming supported as of now and if not, can it be ported over from blackjack, too?

I could also work an a PR to port this functionality, but since I don't know the blackjack code well I would not know where to start.

setzer22 commented 2 years ago

Hi @DerLando! :smile:

I'm happy to share the details of how I achieved the zoom functionality in blackjack, but unfortunately it requires a forked egui backend and it's not something that would be accepted upstream. Basically, it's a hack specific to the wgpu backend, and an ugly one at that: I have two separate egui instances, and render the second instance inside the first as a texture. This also means hijacking the winit integration and translating mouse events, plus adding a few transformations inside egui_wgpu to make sure clip rects are correct when sending them the GPU. On top of that, you need to mess with pixels_per_point at runtime, which can lead to performance issues.

This is why egui_node_graph doesn't support zoom while blackjack does. Because this is currently impossible to do without a very specific application architecture (2 separate egui instances, and a forked backend).

Egui needs a backend-independent mechanism for zooming, but I don't know enough about the egui internals to make that work. Nevertheless, I have reported this to the egui main repo and even volunteered for an implementation: With some guidance, and if someone tells me this has a chance of getting upstreamed, I'll gladly help. But so far things have been quiet.

It might help if you show your support there (even a thumbs up is okay) and expose your use case if you think that's relevant :+1:

DerLando commented 2 years ago

Thanks so much for the quick reply, I had a look at the linked feature request upstream and will add my voice.

I'll close this for now as it will likely require changes upstream.