The Magstep menu controls the document magnification. The default magstep, zero, implies no magnification (i.e. the on-screen image should be the same size as the paper version). Positive magsteps increase the magnification by a factor of 1.2 at each step and negative magsteps decrease the magnification by a factor of 1.2 at each step. The factor of 1.2 is the same factor used by Ghostview (upon which mgv is based) and Ghostview borrowed the factor from TeX: if 1.2 is good enough for Donald Knuth, then it is certainly good enough for me.
The following entries are provided on the menu:
Decrease or increase the magstep factor.
Set the magstep to the specified number; normal means zero magnification. The radio buttons are provided for convenient access to commonly used magsteps. If none of the radio buttons are toggled on, then you have a magstep outside their range.
This pops up a simple dialog which allows you to set a specific magstep value. The Set Magstep dialog can be made sticky.
The current magstep is displayed in, and can be changed from, the status line.
If the magstep is above +5 or below -5, then no radio button will be on but the status line will still show the correct value.
Warning: High magsteps can be pretty hard on your machine: caveat
emptor. If you want to put an upper limit on the magstep, a simple
modification to magstep.c:mgv_ui_magnify() is all that is needed
(just don't make it less than 5 or you'll probably confuse the program).