LockOSThread.md

# Introduction

Some libraries, especially graphical frameworks/libraries like Cocoa, OpenGL, libSDL all require it's
called from the main OS thread or called from the same OS thread due to its use of thread local
data structures. Go's runtime provides ` LockOSThread() ` function for this, but it's notoriously difficult
to use correctly.

# Solutions

Russ Cox presented a good solution for this problem in this [thread](https://groups.google.com/d/msg/golang-nuts/IiWZ2hUuLDA/SNKYYZBelsYJ).

```Go
package sdl

// Arrange that main.main runs on main thread.
func init() {
	runtime.LockOSThread()
}

// Main runs the main SDL service loop.
// The binary's main.main must call sdl.Main() to run this loop.
// Main does not return. If the binary needs to do other work, it
// must do it in separate goroutines.
func Main() {
	for f := range mainfunc {
		f()
	}
}

// queue of work to run in main thread.
var mainfunc = make(chan func())

// do runs f on the main thread.
func do(f func()) {
	done := make(chan bool, 1)
	mainfunc <- func() {
		f()
		done <- true
	}
	<-done
}
```

And then other functions you write in package sdl can be like

```Go
func Beep() {
	do(func() {
		// whatever must run in main thread
	})
}
```