This returns the current screen resolution as a list with two components; width and height.
rp.screenresolution()
One use of this function is to identify the size of the screen so that panels can be constructed top match this using pixel co-ordinates. However, the grid layout system is likely to be a better option in general. See rp.grid
for details of this.
rpanel: Simple interactive controls for R functions using the tcltk package. Journal of Statistical Software, 17, issue 9.