[Freeciv-Dev] patch: techtree support (PR#405)

[David Pfitzner <dwp@xxxxxxxxxxxxxx>]

Apologies for raising a non-release issue at this time, but maybe 
I can justify myself by saying that I intend to release an updated 
version of 'techtree' [1], to coincide with, and suit, freeciv-1.11.0.  
Since the previous version of techtree was for freeciv-1.8.0, this 
is long overdue!

 [1] http://www.mso.anu.edu.au/~dwp/freeciv/techtree/  (old version)

The good part is that I have thought of a good way to have techtree 
be able to cope with current (and even future) ruleset files, without 
copying or sharing lots of code between freeciv and techtree.  The
idea is to add a server command to freeciv, so that freeciv writes
a file with the "distilled" ruleset data needed by techtree, in a
simple and hopefully fixed format that techtree can easily read.

This scheme has a number of advantages:

 - Freeciv is very much able to read current ruleset files, and 
future versions of freeciv can even be expected to be able to read 
future ruleset files :-)  Ie, when formats change etc -- such changes 
should hopefully not even require a new version of techtree, nor a 
techtree re-compile, only a small amount of extra updating within 
freeciv.

 - Freeciv is also well able to calculate the data require by 
techtree, since freeciv has available all the processed data 
structures related to ruleset data.

 - techtree can ignore lots of freeciv-specific stuff, and 
concentrate on calculating the graph and outputing postscript.

 - If desired the intermediate file may be hand-edited, or could be
produced by some other method.  In particular, files could be hand-
produced to create tech-trees for non-freeciv games (SMAC etc?).  
This approach would be easier than trying to mock-up full-size 
freeciv ruleset files just to produce techtree graphs.

 - In principle it may be easy to produce techtree graphs in other
languages, using translations already made for freeciv.  (Ie, just 
run the new freeciv server command using a localised freeciv.)  In 
practice this doesn't work properly yet because I don't currently 
know how to output postscript for non-ascii characters...?  Or maybe 
its a font thing...

Attached is a patch to add a server command 'techtree' to freeciv 
to produce the appropriate output.  My question is whether it would
be reasonable to put this in before 1.11.0 ?  While strictly speaking
this is a new feature, the patch is mostly fairly self-contained, and 
should be unlikely to introduce bugs in other parts of freeciv...  
And it would make things easier for me, and for other techtree 
users :-)

Regards,
-- David

techtree1a.diff.gz
Description: GNU Zip compressed data