raylib-go without cgo (dynamic loading)

[JupiterRider]

With the syscall package in go's standard library or golang.org/x/sys it is already possible to dynamically load libraries without cgo.

Works kinda like this: https://learn.microsoft.com/en-us/windows/win32/dlls/using-run-time-dynamic-linking

Here is a small example, of just displaying a white window:

.
├── go.mod
├── main.go
└── raylib.dll

package main

import (
	"image/color"
	"runtime"
	"syscall"
	"unsafe"
)

func init() {
	runtime.LockOSThread()
}

func main() {
	handle, _ := syscall.LoadLibrary("raylib.dll")
	defer syscall.FreeLibrary(handle)

	initWindow, _ := syscall.GetProcAddress(handle, "InitWindow")
	closeWindow, _ := syscall.GetProcAddress(handle, "CloseWindow")
	windowShouldClose, _ := syscall.GetProcAddress(handle, "WindowShouldClose")
	beginDrawing, _ := syscall.GetProcAddress(handle, "BeginDrawing")
	endDrawing, _ := syscall.GetProcAddress(handle, "EndDrawing")
	clearBackground, _ := syscall.GetProcAddress(handle, "ClearBackground")

	title, _ := syscall.BytePtrFromString("My Game")
	syscall.SyscallN(initWindow, uintptr(1280), uintptr(720), uintptr(unsafe.Pointer(title)))

	for {
		syscall.SyscallN(beginDrawing)
		syscall.SyscallN(clearBackground, *(*uintptr)(unsafe.Pointer(&color.RGBA{255, 255, 255, 255})))
		syscall.SyscallN(endDrawing)
		ret, _, _ := syscall.SyscallN(windowShouldClose)
		close := *(*bool)(unsafe.Pointer(&ret))
		if close {
			break
		}
	}

	syscall.SyscallN(closeWindow)
}

For Linux and MacOS there is a project called "purego": https://github.com/ebitengine/purego
But sadly structs are not supported in purego.
As a workaround you could write wrapper functions or try to get libffi working: ebitengine/purego#88 (comment)

Using dynamic loading would reduce build times and enable cross compiling without any third party c-compiler.

So what do you think?

[gen2brain]

The only viable option for removing cgo seems to be on Windows, where the code to load the dynamic library is in the kernel and not in the libC.

The purego without the structs looks like it would be a real pain. Anyway, if ever done, purego says it can be also used for Windows, so then I would not see a point in having a different code base just for Windows.

It would also remove so many options, we would need one .dll/.so file for every combination, i.e., one for SDL, one for DRM, Wayland, and what about OpenGL versions, etc., or if you want to override something in config.h, etc. Currently having C code included in the repo has many advantages. On the other hand, without cgo, I guess building for Web platform should be possible in theory, now that would be very nice.

There is also one more possible way, to compile raylib library to raylib.wasm with wasi-sdk and then run that with wazero. For example, see https://github.com/yklcs/wasmimg or https://github.com/wasilibs/go-re2. I haven't tried that method yet, but I probably will, with something useful, like libjxl.

[gen2brain]

Btw. raylib for some time has https://github.com/raysan5/raylib/tree/master/parser with JSON output. That can be used to generate some code, at least for start. Doesn't have to be used later on.

[JupiterRider]

Is there some kind of code generator to convert the JSON into golang source code?

[gen2brain]

That is something that would need to be written, especially for purego.

[JupiterRider]

@gen2brain Do you recommend any source code generators for go? Jennifer looks pretty nice: https://github.com/dave/jennifer

[gen2brain]

I don't have experience with any of those.