Re: Question: units of AppKit coordinates.

[Chris Hanson]

On Wednesday, October 15, 2003, at 06:47  PM, Vaisburd, Haim wrote:
> AppKit accepts coordinates as floating point numbers.
> I have drawn a conclusion that they are probably meant
> to be some device-independent units like millimeters
> or inches or something alike.

Coordinates should probably be kept as floating point right up until 
the point they're sent to the back-end.

User-space coordinates in AppKit are considered to be in PostScript 
points, *unless you change the coordinate system*.  In PostScript, 
there are 72 points to the inch.  This is close (but not exactly equal) 
to the typographer's point; there are just over 72 typographer's points 
to the inch.

It should be up to the back-end to translate device-independent 
coordinates into device-dependent coordinates for the particular output 
device in use.  This is going to  be particularly important in the near 
future as users start getting 200dpi displays.  (The cost of a 24-inch 
200dpi widescreen LCD monitor is already down to US$4000 from ViewSonic 
or IBM.)

  -- Chris

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