Creating multiple windows with separate contexts

[medvednikov]

Hi,

Thanks for this great library!

I'd like to have two different windows with different stuff drawn on them. I'm struggling with this. Is there a small example of how to handle multiple windows/multiple contexts?

I found this in a related project:

https://github.com/notlion/Cinder-NanoVG/blob/master/samples/MultiWindow/src/MultiWindowApp.cpp\

Here's what I'm trying to do looks like in pure OpenGL:

foreach w in windows:
    foreach ctx in w.contexts:
        ctx.make_current(w)
        do_opengl_stuff()
        glFlush()

Thanks

[itscool]

I've done this. At first I used a separate NanoVG context and GLFW context per window. However, this leads to weird difficulties down the road. I ended up using shared context. Like so:

glfwShared = glfwCreateWindow(... , nullptr)
glfwMakeContextCurrent(glfwShared)
glExtensionLoader()  // I used GLAD
nvgShared = nvgCreateGL*()

Then for each window:

glfwWins[i] = glfwCreateWindow(... , glfwShared)

Then to render:

foreach w in glfwWins
    glfwMakeContextCurrent(w)
    nvgBeginFrame(nvgShared, ...)
    DO_NVG_RENDERING()
    nvgEndFrame(nvgShared)
    glfwSwapBuffers(w)

This way all resources loaded using NVG are shared between all windows as well.

[medvednikov]

Thanks a lot @itscool. It worked!

[medvednikov]

I actually managed to make it work without sharing the context, and just like @itscool I faced strange bugs (like text not being rendered correctly in the second window).

Shared context FTW!

[EriKWDev]

I actually managed to make it work without sharing the context

While a shared context is nice, I'm having troubles with retaining the transform state. Care to share how you got it to work with multiple contexts?