That is indeed strange.  I presume you mean the button on the top-left of a Display which lets you pull down a menu of layers, correct?  You're saying that clicking this button -- that is, revealing the menu -- causes the simulation to slow down for a while?  This button is nothing more than a JToggleButton which triggers a JPopupMenu.  What operating system are you running? 

This sounds like an OS bug.  The only thing I can think of (the button does _nothing_ but pop up that popup menu, which does _nothing_ unless you check or uncheck something) is that the popup menu obscured a part of the Display2D, causing the OS to start redrawing in a different mode because the drawing area for a little while wasn't square.  That'd be a pretty stupid OS bug.

Try this:

1. Make sure you're using the current version of MASON on SVN, not the tarball, so we can be in sync.
2. In sim/display/Display2D.java there is a line of code (around 1129) which says:

	popup.setLightWeightPopupEnabled(false); 

Set this to true and see what happens.

Beyond this I will need an example.  You can mail it to me but beware that my turnaround is bad for the next two weeks because I'm in Italy with a limited internet connection.

Sean

On Aug 7, 2012, at 7:27 AM, Andrew Reilly wrote:

> I have a simple simulation where agents have a field that is set initially at a 
> random number and then increases by one with every step. The portrayal showing 
> the value of this field shows the values growing in colour intensity until the value 
> crosses the maximum value set in the SimpleColorMap class constructor. 
> 
> If the simulation is run, stopped and run again, everything is fine. But if at any 
> point the "Show Layers" button is pressed, regardless of whether or not any of 
> the checkboxes indicating the layers are checked or unchecked, the simulation 
> slows down until the agent field values cross the maximum value. As each agent 
> reaches this maximum the simulation starts to speed up again, and once all 
> agents have crossed it the simulation runs as normal. It will still do this even 
> when it is stopped and restarted again. Simply clicking on that button once will 
> have this effect until the whole application is closed down.
> 
> Why does clicking on this button have this effect?