Senior software engineer with 9+ years of experience. Eschew hype; focus on delivery and performance.

Co-founder and lead engineer at Gadget Software in addition to my day job.

Living in Switzerland 🇨🇭 since 2017.

Drawing text on a window with Odin - Part 1: GLFW

Based in great part on the following code, thank you to the original author!

GLFW, OpenGL Window Tutorial in Odin language

package main

import "core:fmt"
import "core:c"
import "vendor:glfw"
import gl "vendor:OpenGL"

GL_MAJOR_VERSION :: 4
GL_MINOR_VERSION :: 1

should_exit := false

main :: proc() {
	fmt.println("Hellope!")

	if glfw.Init() != glfw.TRUE {
		fmt.println("Failed to initialize GLFW")
		return
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.RESIZABLE, glfw.TRUE)
	glfw.WindowHint(glfw.OPENGL_FORWARD_COMPAT, glfw.TRUE)
	glfw.WindowHint(glfw.OPENGL_PROFILE, glfw.OPENGL_CORE_PROFILE)
	glfw.WindowHint(glfw.CONTEXT_VERSION_MAJOR, GL_MAJOR_VERSION)
	glfw.WindowHint(glfw.CONTEXT_VERSION_MINOR, GL_MINOR_VERSION)

	window := glfw.CreateWindow(640, 480, "Todo", nil, nil)
	defer glfw.DestroyWindow(window)

	if window == nil {
		fmt.println("Unable to create window")
		return
	}

	glfw.MakeContextCurrent(window)

	// Enable vsync
	glfw.SwapInterval(1)

	glfw.SetKeyCallback(window, key_callback)
	glfw.SetMouseButtonCallback(window, mouse_callback)
	glfw.SetCursorPosCallback(window, cursor_position_callback)
	glfw.SetFramebufferSizeCallback(window, framebuffer_size_callback)

	gl.load_up_to(GL_MAJOR_VERSION, GL_MINOR_VERSION, glfw.gl_set_proc_address)

	for !glfw.WindowShouldClose(window) && !should_exit {
		gl.ClearColor(0.2, 0.3, 0.3, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT) // clear with the color set above

		glfw.SwapBuffers(window)
		glfw.PollEvents()
	}
}

key_callback :: proc "c" (window: glfw.WindowHandle, key, scancode, action, mods: i32) {
	if key == glfw.KEY_ESCAPE && action == glfw.PRESS {
		should_exit = true
	}
}

mouse_callback :: proc "c" (window: glfw.WindowHandle, button, action, mods: i32) {}

cursor_position_callback :: proc "c" (window: glfw.WindowHandle, xpos, ypos: f64) {}

scroll_callback :: proc "c" (window: glfw.WindowHandle, xoffset, yoffset: f64) {}

framebuffer_size_callback :: proc "c" (window: glfw.WindowHandle, width, height: i32) {}

There are actually some changes we need to make from the above code though.

  1. Your window hints have to be after the glfw init. Otherwise, it will crash.
  2. The original code is missing some hints for macOS and they're in the wrong order.

In macOS one needs to specify GLFW_OPENGL_FORWARD_COMPAT and GLFW_OPENGL_PROFILE BEFORE the GLFW_CONTEXT_VERSION_MAJOR and GLFW_CONTEXT_VERSION_MINOR hints.

GLFW docs specify as much:

macOS: The OS only supports forward-compatible core profile contexts for OpenGL versions 3.2 and later. Before creating an OpenGL context of version 3.2 or later you must set the GLFW_OPENGL_FORWARD_COMPAT and GLFW_OPENGL_PROFILE hints accordingly. OpenGL 3.0 and 3.1 contexts are not supported at all on macOS.