Transfer/Rebind OpenGL Context between Windows

[Baedrick]

This function seems to be missing from RGFW OpenGL context manipulation functions.

RGFWDEF void RGFW_window_setContext_OpenGL(RGFW_window* win, RGFW_glContext* ctx);

It would be useful for migrating the active context previously set up by bootstrapping some code when setting up a rendering backend. The implementation would be like this.

void RGFW_window_setContext_OpenGL(RGFW_window* win, RGFW_glContext* ctx) {
	win->src.ctx.native = ctx;
	win->src.gfxType = RGFW_gfxNativeOpenGL;
}

[ColleagueRiley]

This generally isn't possible with the current implementation. Unlike other graphics APIs, to create a OpenGL context, both the OpenGL context and the window must agree on a format. This is sometimes called Visual or pixel format or view.

In order for this to work, RGFW would need to save the format and change it when the user wants to transfer contexts.

[Baedrick]

I see, I would argue that this is an advanced usage and the average user wouldn't really be using this function. Advanced users would know that limitation and understand the constraints, like having the same formats between windows.

[ColleagueRiley]

On X11, this isn't really possible because the Visual has to be set on window creation. However RGFW already uses a hack by making new window when the context is created, if it wasn't created with the window already.

I also wouldn't be surprised if sharing a context between multiple windows, or switching a context from one window to another, would create bugs between platforms and drivers. Generally, one context per window seems to be the best approach, and there is a flag if you want to share resources across contexts.

[ColleagueRiley]

I see, I would argue that this is an advanced usage and the average user wouldn't really be using this function. Advanced users would know that limitation and understand the constraints, like having the same formats between windows.

Users have no control of the window format. For each API, there is a OpenGL function for creating a format for that specific Window. OpenGL isn't as nice to work with as Vulkan for cases like this, it requires a lot more platform specific integration. Which is why RGFW includes these functions.

[ColleagueRiley]

My point isn't to say that this is necessarily a bad idea. Just that it is far more complicated than it might initially seem.