Re: porting Xlib/Motif apps to GTK+

[jcupitt gmail com]

Hi Roger,

I moved a medium-sized (100k lines) application from Motif/X11 to gtk+
a while ago.

As you say, gdk_ is a thin layer over the X11 drawing system, so
converting that is pretty easy. Gdk has quite a few helpers too, eg.
stuff for rendering a 24-bit image to whatever visual the server has,
so you can save some code there. It shouldn't be a huge effort to
port.

A quick port of your GUI code should be fairly easy too. You'll end up
with a not-very-gtk-ish program but, as long as it works, perhaps
that's OK. Prettying it up could be a long-term, low-priority effort.
Gtk has a nice GUI builder which could save you some effort, it'd be
worth experimenting with. You could also consider using Python,
JavaScript or equivalent for the top-level GUI and only using C for
the low-level stuff. Gtk3 seems to be heading very rapidly in this
direction.

I make Windows binaries for my program with a cross-compiler on Linux.
It works really well, I can get a nightly build, including a setup.exe
installer, uploaded automatically to my server. The Windows backend
does not implement all of gdk (the stippling modes are missing, for
example) which can be annoying.

I make an OS X binary on OS X with the Quartz backend. It also works
well, though you end up with a program that looks rather out of place
on the Mac desktop unless you do quite a bit of platform-specific
stuff. Again, it's easy to package automatically as a .dmg containing
a .app.

I used to try to make binaries for the various *nix platforms, but
it's a huge effort and not very reliable. IMO a tarball plus
build-it-yourself instructions is best. If your program is useful the
distributions will pick it up and package it for you. You could
support one distribution (eg. centos6) yourself I guess.

Once you have the thing basically working you could think about more
dramatic rewriting. As you say, switching to Cairo is going to be
necessary at some point.

Good luck!

John