[cairo] Compiling cairo against winelib, to enable win32 testing on Linux

[Behdad Esfahbod]

I got this idea to use winelib to compile the win32 backend on Linux.
Carl and I both have the feeling that even being able to just compile
(and not run/test) the win32 (and other) backends increases the quality
of our releases because we would know that we've not broken something
very silly for the least.

So I started looking into this.  Documentation for winelib is four years
old, to say the least.  So I had to do lots of trials and see how wine
builds its dlls itself to find my way out.  In the end, it doesn't look
that bad, though not as good as I thought either.

I pushed some changes to master that enable using winelib by just doing:

./configure CC=winegcc LD=winegcc

You can turn off the win32 font backend, if you want, by doing
--disable-win32-font.  The main problem with the build system at this
point though is that libtool decides that winelib cannot make shared
libraries.  So it builds static libs only.  I'll look into fixing that
later.

Next problem I still have is that pdf2png and svg2png won't link now.
Not sure why's that.  Also note that binaries generated by winegcc are
in fact a small script calling wine to load the actualy .exe.so file
generated.  This is not much worse than what libtool already does for
us, but we may be able to get to plain binaries since we don't use any
native Windows binaries and so the wine loader should not be necessary.

Finally, running the test suite.  First, for an unknown reason, it
crashes if $DISPLAY is set.  It does so in a gdi32.something_flush
function.  Interestingly, if I unset DISPLAY, it kinda works now.  The
font stuff doesn't look good, so I turned win32-font backend off and
used freetype.  The other major problem is that it seems like some kind
of composite operations are ignored.  The most evident effect of this is
that about 50 tests fail, and most have a totally black output image.
In some testing that I did, painting an image surface to a win32 surface
works, but simply painting a solid color to it doesn't work.  Wine
bug...


Anyway, just wanted to give a heads up, and I'll be looking into this
stuff a bit more, but those familiar with windows and wine stuff feel
free to give this a try and improve it.  Good test for wine in fact.  I
hope they pick this up and fix their stuff.

-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759