videocommon: UpdateDrawRectangle cleanup

I felt this code was pretty messy so I wanted to clean it up a bit. I have tested it by changing all the graphic setting options but I am unsure if that is enough. If someone could verify I havent screwed up that would be helpful.
You're using ? on the result of a division whereas it should be used where the result is a bool.  Maybe split this line up into multiple lines so that it is easier to read.