Is it possible to pass ProcAddress into a ktx library?

[Logickin-Lambda]

I am currently trying to figure out how to use ktx library provided by the KhronosGroup, and seem I have faced an issue on initialize the library.

The library is written in C, so I have used a C import:

const c = @cImport({
    @cInclude("ktx.h");
});

To build the project, I have pointed the header file in in build.zig as shown:

exe.addIncludePath(.{ .cwd_relative = "C:\\Program Files\\KTX-Software\\include" });

In the official documentation, before running any the load function, I need to run function ktxLoadOpenGL( PFNGLGETPROCADDRESS pfnGLGetProcAddress) to initialize the library before using the load function, and seems that the input parameter PFNGLGETPROCADDRESS pfnGLGetProcAddress is a kind of GLGetProcAddress function. For that reason, I decided to past the function glfw.getProcAddress because this is the only function with the same name.

However, this function is not matched to the input of ktxLoadOpenGL because the following error:

error: expected type 
  '*const fn ([*c]const u8) callconv(.c) ?*const fn () callconv(.c) void', 
found 
  '*const fn ([*:0]const u8) callconv(.c) ?*const anyopaque'

Seems like the ktx library accepts a precise return type instead of anyopaque, so here are the questions:

• Did I pass the wrong ProcAddress into the KTX library?
• If so, what is the equivalent? If not, is there a way to convert the return type such that I can initialize the function?
• Have you worked on KTX texture with zig before? If you did, I wish to see if you could have some better ideas on handling those textures.

[carrot-sticks]

I don't think that you have passed the wrong function, getProcAddress is the function, which when called with function name, will return a pointer to that function.

In Kronos docs (const char *proc), and ?*const fn () callconv(.c) void here is the said function. You should just cast pointer to the function.

const c = @cImport({
    @cInclude("ktx.h");
});

\\ ...

c.ktxLoadOpenGL(@ptrCast(glfw.getProcAddress));

But I do think that we probably should match the type with GLFW typedef, which is typedef void (*GLFWglproc)(void);

[Logickin-Lambda]

Thank you! Although I no longer learn OpenGL from the Superbible which I was intended to use it for imgui when I didn't aware of the zgpu and the zgui library in zig-gamedev, I will try that in some point of time to see if this works.