wgpu backend

[IceSentry]

I was trying to create a plugin for https://github.com/bevyengine/bevy and that would require a wgpu backend I think. I'd be interested in working on this, but I have no idea where to start.

[emilk]

Hello!

A good place to start is probably to look at how the rendering is done for Glium: https://github.com/emilk/egui/blob/master/egui_glium/src/painter.rs

[IceSentry]

So I've been working on my implementation here https://github.com/IceSentry/bevy_prototype_egui_plugin

I was about to start the painter based on glium, but I keep getting a crash saying No fonts available. I've been looking everywhere in the glium examples and egui_glium and I can't figure out how fonts are loaded.

[IceSentry]

Also, just to be sure. it seems like implementing App and Backend isn't actually required. Is this true or did I miss something?

[IceSentry]

I figured out my font bug. It was an issue with the ordering of the update calls.

[emilk]

it seems like implementing App and Backend isn't actually required

You are correct!

egui::app is a model I introduced for writing backend agnostic apps. The goal is that you can write e.g. a calculator app that implements egui::app::App and then easily compile it for different Egui backends that implements egui::app::Backend (such as egui_glium and egui_web). It is still quite experimental.

[emilk]

I've added this section to README.md:

You need to collect egui::RawInput, paint egui::PaintJobs and handle egui::Output. The basic structure is this:

let mut egui_ctx = egui::Context::new();

// game loop:
loop {
    let raw_input: egui::RawInput = my_backend.gather_input();
    let mut ui = egui_ctx.begin_frame(raw_input);
    my_app.ui(&mut ui); // add windows and widgets to `ui` here
    let (output, paint_jobs) = egui_ctx.end_frame();
    my_backend.paint(paint_jobs);
    my_backend.set_cursor_icon(output.cursor_icon);
    // Also see `egui::Output` for more
}

[IceSentry]

I saw that, thank you, it was helpful. Now I just need to figure out how to draw the triangles in bevy and I think I'll be set.

[Gonkalbell]

I just uploaded https://github.com/Gonkalbell/egui_wgpu, which is a pretty lazy port of the glium bindings. I haven't gotten around to uploading the documentation to docs.rs or publishing this to crates.io yet, but maybe you can find it useful.

[IceSentry]

Oh cool, thanks, I'll look at it. I kind of stopped working on this.

[emilk]

It seems like we have TWO wgpu backends for Egui now:

• https://github.com/hasenbanck/egui_wgpu_backend (https://crates.io/crates/egui_wgpu_backend)
• https://github.com/Gonkalbell/egui_winit_wgpu (unpublished)

So I will consider this issue closed!