[Xr] Default scaling matrix
Bill Spitzak
spitzak at d2.com
Wed May 21 23:56:00 PDT 2003
An idea I had on the uwin.org list.
1. To do exact device-independent scaling of the output, instead of having
some call that returns "dpi", have a call similar to XrDefaultMatrix() and
XrIdentityMatrix() that sets a matrix that is scaled to a known dimension,
probably 1/72 of an inch to match Postscript, though maybe it should be 1mm
(do *not* supply more than one call as somebody will mess up their driver and
get the relative scales wrong) This is no big deal but it seems a lot cleaner
to me as it does not involve a return value, and anybody who wants to know
the real dpi can read the matrix.
2. On a related note, is the Identity matrix device-specific? What I mean are
devices where it is convienent for the location 0,0 to be somewhere other
than the lower-left corner, and the x and y directions may be reversed or
swapped. In that case is the identity matrix not the math identity?
Alternatively, are these sort of transformations required to be done
invisibly inside the driver, or conversely is the identity matrix allowed to
orient the output in any direction?
--
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/\_ _|_========___ Bill Spitzak
~~~/\/\\~~~~~~\____________/~~~~~~~~ spitzak at d2.com
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