I've used inferior packages that enjoy rounding errors. Zooming on the screen, converting from imperial to metric and tracks don't meet up. Gerber output files contain fraction errors that the manufacturer has to clean up.
There is no need for this stupidity. I need to use a common base unit for imperial and metric.
1" is 2.54 mm. Working to "one thou" seems an adequate number. Production tolerances aren't that good. I'll use an internal resolution unit of 1/ 254000". A "Weeney". The user will not see these units, only imperial or metric representations of them.
254 Weeneys is a thou.
25400 Weeneys is 0.1".
10000 Weeneys is 1mm.
100000 Weeneys is 1cm.
Or how big can the board be using this excessively fine resolution?
Win32 uses 32bit integers. The GDI and MFC class library uses signed integers. I've got 231 to play with. 231 / 254000 is 8454.6" or just over a furlong. This is entirely adequate!