Re: [Groff] Device-independence of intermediate output

[Bernd Warken]

On Thu, Jan 31, 2002 at 08:02:43AM +0100, Werner LEMBERG wrote:
> 
> Compatibility is always a good thing IMHO.  Please give more details.
> 

Suppose you've got some intermediate output generated by some roff 
formatter; you want to feed this into some groff device different from
the one specified in the output.

Classical troff documented a scaling facility that allowed to translate
the output for one device to any other native device by resolution 
scaling - with a small loss of precision due to integer rounding.
It is easy to implement this for groff.

It will be a bit harder to extend this concept further to support
arbitrary non-groff devices.  This could be left for a second stage.

The rough structure of the device/resolution translation between groff
devices is as follows.

- Everything can be done within src/libs/libdriver/input.cc.

- I use a preprocessor macro during the test phase to shield off the
resolution translation.

- The resolution translation is triggered as soon as the resolution
provided with the `x r' command differs from the device's resolution.

- The command arguments that need to be scaled are positional offsets,
while color values, font positions, character codes, etc. are not
scaled. 

There are some subtle issues that I would like to discuss at a later 
stage.  Thanks for helping.

Bernd Warken