We (Apple developers) run the latest Mac OS (10.5.6 as of this writing) with the latest version of Matlab (7.6 as of this writing) or (Linux developers) Ubuntu 64-bit (Gutsy) and 32-bit (Feisty) with Matlab 7.4 and the binaries are created to run on these systems. As noted above, some older versions (notably Matlab 14.1) are not able to use these mex files and crash when you try to run mglOpen. If this happens, then all you need to do is recompile MGL using mglMake(1).

The Matlab license manager checks every 30 seconds for the license. This can cause there to be an apparent frame glitch in your stimulus code, especially if you are using a network license (on our machines it can take ~200 ms to check for the license). The only known workaround to this is to run on a machine that has a local copy of the license. You can check this for yourself by seeing how long it takes to do screen refreshes:

 mglOpen;
 global MGL;
 checkTime = 30*MGL.frameRate;
 timeTaken = zeros(1,checkTime);
 mglFlush;
 for i = 1:checkTime
   flushStart = mglGetSecs;
   mglFlush;
   timeTaken(i) = mglGetSecs(flushStart);
 end 
 mglClose;
 plot((1:checkTime)/MGL.frameRate,timeTaken);
 zoom on;xlabel('seconds');ylabel('Frame refresh time (seconds)');

If you have the same problem, you should see one large spike in the time course like this:

This one shows it taking about 65 ms. Note that you may see small deviations in which one frame takes longer and then the following frame takes shorter than the mean. These are normal flucations persumably due to multi-tasking and other events that are intermittently taking up time. As long as these are shorter than a frame refresh interval minus the time it takes you to process the stimuli for your display, you will not drop any frames. Note that in the above code, if you change mglFlush to any other command, such as WaitSecs(1/frameRate);, you will still see the big spike for the license manager check–confirming that this has nothing to do with drawing to the screen.

Not all functions are currently supported on the Linux platform. The list of funcitons not supported yet are:

• mglText
• mglTextDraw
• mglPlaySound
• mglInstallSound
• mglDescribeDisplays
• mglSwitchDisplay
• mglListener

If you want to use text under the linux operating system, you can use mglStrokeText.

Here is a more recent update from Jonas about the Linux version:

I am in the process of upgrading the Linux version of MGL to run under Ubuntu (64-bit and 32-bit) with NVIDIA and ATI graphics cards. Although the upgrade is still incomplete, most functions work equally well under Linux at this stage. Some differences that will remain between the platforms are listed below.

• no support for font-based text - this needs to be upgraded, I started looking into using FreeType for this which is widely available and would be easy to implement in the same texture-based way that the Mac code relies on. Care must be taken to ensure that the code is maximally portable across platforms, so it may be that some Mac-specific idiosyncracies need to be modified
• note that the stroke text works perfectly under Linux, so unless you are very enamoured with a specific font this is a perfectly usable workaround (though some symbols, eg %, are missing currently)
• some differences in the way you specify special keys, but this is generally to Linux' advantage - eg you can use ESC, BACKSPACE etc as names (relies on the XKeySymDef.h or sth like that)
• timing is in general more accurate on Linux, since the clock rate is much higher on modern systems (100-500Hz vs 60Hz on the Mac)
• no parallel port interface yet so you can't use Justin's code for calibration
• no sound - need to decide on a standard to use that is most widely available
• the syncing with OpenGL is idiosyncratic and depends on the graphics card. I have implemented this to use both the SGI video sync extension and the environment variable (both NVIDIA and ATI provide this option). The former is not supported by all OpenGL cards (though most modern ones) and can interact with the environment variable option, so I will make the latter the default, with an option to use the SGI extension when compiling only.

For the time being, only NVIDIA and ATI cards will be supported (because I only have access to those two machines).

• setting screen size and resolution requires the XRandR extension, which is supported on recent X distributions (Xorg 7.0 and later). Older X servers (eg Apple's X11) won't work.
• you need to reuse the X display or you run into memory problems, and the code for doing this needs to be checked for consistency. This is similar to the Mac window situation and relates to the uneasy relationship between Matlab and X. When you open a window, the MGL global variable will contain a window and display pointer that is used on subsequent calls; care must be taken not to clear the MGL variable between calls (once you do so, running MGL is likely to crash Matlab, even if you run clear all, which correctly closes the display).

• mglSetRandR allows you to set and get resolution and refresh rate from the command line. There is no support for Mac at present; use the Display Manager.

This issue had been resolved, but if you find you are still having problems, here is what the issue was and how to resolve it:

On Mac OS X there seems to be some interaction with having mutliple threads in the workspace that causes working within a window (i.e. mglOpen(0) as opposed to fullscreen) to be unstable. The workaround for now is not to close the window once it is opened. This seems to work fairly well. When one is completely finished working with the window, one can call mglPrivateClose to close the window. But after that, calling mglOpen(0) is likely to crash.

mglOpen(0) works fine if running matlab -nojvm or -nodesktop.

On Mac OS X if you want to get key press events, you can get them with a system (nanosecond precision) time stamp in the 2.0 beta. For the previous version of mgl you could only get them with a resolution of 1/60 second. If you are willing to sit in a loop testing the keyboard, you can use mglGetKeys and get acceptable time resolution (your time resolution will depend on how fast you poll the keyboard status). On Linux, the time resolution depends on the kernel's hard-coded HZ setting, which is usually between 100-500; the value can be retrieved (at least on Ubuntu) by typing cat /boot/config-`uname -r` | grep '^CONFIG_HZ=' The time resolution is 1/HZ sec; so on the current developer system, with HZ=250, key presses can be timed with a resolution of 1/250=4msec.

The default version of mgl runs on 64 bit Matlab. An older version (v1.5) will only run on 32-bit Matlab.

If you have Matlab 7.9 or greater installed, matlab defaults to running in 64 bit mode, but you can set it to run in 32 bit mode - though with the current version of mgl you do not need to do this:

1. Finder Go find the Matlab executable (somewhere like: /Applications/MATLAB_R2009b.app/bin/matlab) then click on it and “Get Info” by selecting and hitting “Command-I”. Then click “Start in 32-bit mode”.
2. Command line Run using a flag: matlab -maci