Custom opengl provider

[Dreaming-Codes]

I'm trying to render slint over an existing opengl context. With egui which uses glow I'm able to acchieve this by doing:

class OpenGlProvider: OpenGlProcAddressProvider {
	override fun byString(name: String): Long {
		return GL.getFunctionProvider()!!.getFunctionAddress(name)
	}
}

pub fn init_glow(opengl_provider: Arc<dyn OpenGlProcAddressProvider>) {
    let gl = unsafe {
        glow::Context::from_loader_function(|name| {
            opengl_provider.by_string(name.to_string()) as *const std::os::raw::c_void
        })
    };
}

Is there any simple way to achieve the same thing with slint?

I think #6510 is related

[ogoffart]

I'm not sure if you are asking something like the opengl_underlay example, https://github.com/slint-ui/slint/tree/master/examples/opengl_underlay
Or making your own slint::platform::Platform using FemtoVGRenderer

[Dreaming-Codes]

2nd one I'm trying to use slint for a Minecraft mod which uses glfw (opengl). I'm calling rust using JNI

[Dreaming-Codes]

@ogoffart I'm unsure how to implement certain platform-specific details. Specifically, the methods related to the event loop are unclear, as I already have an existing event loop in place for rendering within an existing app.

[ogoffart]

If you have already an existing event loop, you can skip the re-implementation of the run_event_loop
See documentation in https://docs.rs/slint/latest/slint/docs/mcu/index.html#the-event-loop
But you would not have a loop, but instead you'd call the slint::platform::update_timers_and_animations and window.try_dispatch_event from the existing event loop.

[Dreaming-Codes]

@ogoffart Hey! I managed to render Slint on top of Minecraft, but I'm running into an issue where it flickers, almost like it’s not drawing fast enough. From what I’ve seen in other implementations of Slint, there’s usually an approach where it only redraws on changes. However, since Minecraft redraws the entire canvas every frame, I’ve been calling the render method on each iteration of the render loop.

Is this rendering method just not ideal for Slint? Would it be better to render Slint to a texture in the shared opengl context and then overlay it on top of Minecraft to avoid unnecessary render calls? Or am I missing something here?