# GLFW 3.X head on OSX -- \[53365:c03\] NSMapGet: map table argument is NULL

**URL:** <https://discourse.glfw.org/t/glfw-3-x-head-on-osx-53365-c03-nsmapget-map-table-argument-is-null/524>\
**Category:** support\
**Created:** [January 30, 2013, 10:23am UTC](https://discourse.glfw.org/t/glfw-3-x-head-on-osx-53365-c03-nsmapget-map-table-argument-is-null/524 "2013-01-30T10:23:31Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![system](https://canada1.discourse-cdn.com/flex035/uploads/glfw/original/1X/b8cdefe6b61b8d5aee6c43b2c56e9cf5eabecfe4.svg) [@system](https://discourse.glfw.org/u/system)\
**Post date:** [January 30, 2013, 10:23am UTC](https://discourse.glfw.org/t/glfw-3-x-head-on-osx-53365-c03-nsmapget-map-table-argument-is-null/524/1 "2013-01-30T10:23:31Z")

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**anonymous** wrote on [Wednesday, January 30, 2013](https://sourceforge.net/p/glfw/discussion/247562/thread/c5bedd96/#5a04):

Hi there,

I’m digging into a bug in the handling of external monitors in GLFW 3.x (taken 2 days ago from the Git repo head).

First, I’m getting all available monitors with glfwGetMonitors. The info I’m getting is:

```
Monitor 0, res: 1920x1080 // This is the external monitor
Monitor 1, res: 1280x800 // Laptop monitor

```

I’ve configured OSX to setup the external monitor as the primary one, so what GLFW is returning here makes sense.

Now, if I try creating a fullscreen window with that data, GLFW just goes nuts. If I use monitor0, it just barfs the error in the topic title, and fails to create the window. If I use monitor1 it does create a window, but it does so on the external monitor instead of the laptop one as I requested.

Finally, after configuring OSX to setup the laptop screen as the main monitor I get this info:

```
Monitor 0, res: 1280x800
Monitor 1, res: 1920x1080

```

Again, this makes sense.

But now the behavior is reversed: selecting monitor0 creates a window on the laptop screen (as it should), but if I try monitor1 it just shows the NSMapGet error and fails.

I have no problems with windowed mode, and everything works fine if I don’t plug in the external monitor.

Hope this helps!

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<div class="post-metadata">

**Author:** ![system](https://canada1.discourse-cdn.com/flex035/uploads/glfw/original/1X/b8cdefe6b61b8d5aee6c43b2c56e9cf5eabecfe4.svg) [@system](https://discourse.glfw.org/u/system)\
**Post date:** [March 19, 2013, 11:01pm UTC](https://discourse.glfw.org/t/glfw-3-x-head-on-osx-53365-c03-nsmapget-map-table-argument-is-null/524/2 "2013-03-19T23:01:17Z")

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**[elmindreda](https://sourceforge.net/u/elmindreda/)** wrote on [Tuesday, March 19, 2013](https://sourceforge.net/p/glfw/discussion/247562/thread/c5bedd96/#656b):

There are still plenty of bugs in the OS X implementation of multi-monitor support in GLFW 3. It will be taken care of before release, but currently it doesn’t work very well.