CLAP with GLFW or SDL?

[nukelash]

Hi, I'm interested in writing a plug-in using the CLAP API (I've written some with JUCE before) and am looking at ways to generate the GUI. I came across this repository which uses Dear ImGui/GLFW (https://github.com/schwaaa/clap-imgui) but also this thread in which someone calls it a dead-end (https://www.kvraudio.com/forum/viewtopic.php?t=583140&start=420)

They say the reason it's a dead end is because GLFW can only have 1 window, but it clearly does have support for multiple windows: https://discourse.glfw.org/t/how-to-create-multiple-window/1398

So what is it that actually makes these libraries incompatible? Or is it worth investigating? What about SDL?

[skuyuy]

GLFW handles your window management if you dont actually have a window yet. Since the host usually provides one for you as the plugin you should not need to use either of these and only handle rendering on the provided window (see the gui extension)
(DEVs feel free to correct me)

[nukelash]

I see, okay thanks.
Follow up question then, if I wanted to use openGL for rendering, any idea where I could begin? Looking at gui.h extension, while I see functions for creating/destroying the gui, I don't see anything like a render() function where I could do the actual drawing.

[skuyuy]

just looked at the clap-imgui example and TBH if you really need more than one window i would use SDL but otherwise stick to glfw to do the setup for you and just do what clap-imgui does

the problem about only having one window available relates to creating a window yourself but creating an OpenGL context for a window that is already provided to you should be no problem

[baconpaul]

I made clap saw demo work with SDL2 more or less a couple of years ago but never pushed the code to GitHub. If you want to see it and finish what i started I could push it to a private repo.

when schwa frank and i were looking at imgui it only supported a single window. they have updated that and the clap ingot example works. https://github.com/free-audio/clap-saw-demo-imgui

[Alloyed]

here's a full example using SDL3 (+ opengl):

https://codeberg.org/alloyed/KitsBlips/src/branch/main/kitgui/src/impl/sdl/contextImpl.cpp

caveats: This can't work on Mac OS without changes to SDL itself, and while I think it's possible to work on windows i found it harder and more fiddly than just working with the windows API directly.

Why it can't work on MacOS: libsdl-org/SDL#12141

The reason it can't work on windows is that many hosts (including bitwig) don't implement CLAP_EXT_TIMER_SUPPORT, which means to get a proper windows timer you need to override the windows event loop. SDL does have hooks for this technically, but this was too fiddly for me :p as mentioned. there's a different file in that folder that does windows.

I think pugl is an interesting alternative, but i found out about it way too late, so the version in that folder is basically a single day's experiment that didn't totally work.

[baconpaul]

FYI: For windows and macOS where there's a single UI thread and a base UI library, folks use SetTimer or CFTimerBlah on win and mac (or the proxies to them through juce etc...) rather than relying on the host. The host timer provisioning is really to deal with the fact that there is no central single ui thread on linux like on mac and win, and there is no event programming model for the ui which is singular like win32 and cocoa are.

Defacto the timer and posix fd extensions are for systems without cocoa and win32.

[nukelash]

Interesting, I didn't know that hosts could choose not to support individual extensions. Is there some sort of compatibility matrix that outlines what each host supports?
I was able to successfully make a clap UI with Raylib this weekend on macos, which was a fun project, but it uses the timer extension for the draw calls so it would be good to know how widely or (narrowly) supported that approach is

[baconpaul]

I think very few macOS hosts implement timer, again since CFTimer is there.

We had a matrix for a while I think but really the responsibility of the plugin is to do the probe and check and handle.

Like i said, defacto timer and posix_fd are for linux where there's no central thread and you need to integrate with the host epoll or whatever