I have an application (filerunner on Sourceforge) that pops up 'tooltips' or balloon help messages. To do this it needs to know where the display boundries are. This is especially true of multi head systems. The code I have written to attempt to determine this is slow, must account for different windowing systems and seems to depend on hidden and unknown (at least to me) timings in the display system and is way too big.
It seems to me that at some level Tk knows this information and could just put a documented name on it.
To give an idea of what I needed to do, I have attached the code I wrote. Just reading the comments should give you an idea of the problem.