xcffib

xcffib is intended to be a (mostly) drop-in replacement for xpyb. xpyb
has an inactive upstream, several memory leaks, is python2 only and doesn't
have pypy support. xcffib is a binding which uses
cffi, which mitigates some of the issues
described above. xcffib also builds bindings for 27 of the 29 (xprint and xkb
are missing) X extensions in 1.10.

Installation

For most end users of software that depends on xcffib or developers writing
code against xcffib, you can use the version of xcffib on pypi. To install it,
you'll need libxcb's headers and libxcb-render's headers (these are available
via sudo apt-get install libxcb-render0-dev on Ubuntu). Once you have the C
headers installed, you can just pip install xcffib.

If you're interested in doing development, read on...

Development dependencies

You should be able to install all the language deps from hackage or pip. The
.travis.yaml has an
example of how to install the dependencies on Ubuntu flavors.

Hacking

See the Makefile for
examples on how to run the tests. Your contribution should at pass make check
before it can be merged. The newtests make target can be used to regenerate
expected haskell test data if the tests are failing because you made a change
to the generated python code.

Hacking on new xcb-proto versions

Sometimes (more often recently), xcb-proto makes some updates that we need to
do some work for. These often require some updates to xcb-types as well.
First, hack your changes into xcb-types and cabal install them, then git
clone the version of xcb-proto you want to somewhere, e.g. ~/packages:

~/packages $ git clone http://anongit.freedesktop.org/git/xcb/proto.git xcb-proto`

Finally, you can build/test xcffib against this custom version of
xcb-{proto, types} with:

make XCBDIR=~/packages/xcb-proto/src check

Differences

In general, you should s/xcb/xcffib/g. Explicit differences are listed below,
however I don't think these will prevent any porting, because these were either
not public APIs, or not actually generated (in the case of the exceptions) by
xpyb. I think most porting should Just Work via the regex above.

• xcb.Exception is spelled xcffib.XcffibException and is also a parent of
  all exceptions generated by xcffib.
• xcb.ConnectException is gone, it was unused
• xcffib.ConnectionException is raised on connection errors
• xcb.Iterator is gone; similar functionality is implemented by
  xcffib.pack_list.
• xcb.Request is gone. It was an entirely internal and unnecessary interface.
• xcffib.Connection.send_request takes slightly different (but more sensible)
  arguments.
• Everywhere xcb-proto says char, xcffib uses a char. That means on input
  for a <list type="char"/>, you can use a python string literal. xcffib
  also gives you a string of length 1 out for each element in such a list,
  instead of an int. Finally, there is a helper method called to_string on
  xcffib.List, to convert these string-like things into native strings. In
  both python2 and python3 you get a native str. This means that for things
  like xproto.STR, you can just do the_str.name.to_string() instead of
  ''.join(map(chr, the_str.name)).
• As above, void is also packed/unpacked as chars, since the convention is
  to use it as string data, e.g. in xproto.ChangeProperty.
• The submodule xcb is gone. The top module re-exported all these constants
  anyway, so they live there now. i.e. xcb.xcb.CurrentTime is now just
  xcffib.CurrentTime.

Enhancements

• When sending requests with nested structs you no longer have to pack the
  contents yourself. For example, when calling xproto.FillPoly, you used to
  have to convert the POINTs you were passing in to some sort of buffer which
  had them struct.pack'd. Now, you can just pass an iterable (or
  xcffib.List) of POINTs and it will be automatically packed for you.

• Most of the lower level XCB connection primitives that were previously not
  exposed are now available via xcffib.{ffi,C}, assuming you want to go out
  of band of the binding.

• Checked vs. Unchecked requests are still supported (via Checked and Unchecked
  function calls). However, there is also an additional optional parameter
  is_checked to each request function, to allow you to set the checked status
  that way. Additionally, requests that are (un)checked by default, e.g.
  QueryTree (CreateWindow), have a QueryTreeChecked
  (CreateWindowUnchecked) version which just has the same default behavior.

• The FooError BadFoo duality is gone; it was difficult to understand what
  to actually catch if you wanted to handle an error. Instead, FooError and
  BadFoo are aliases, and both implement the X error object description and
  python Exception (via inheriting from XcffibException).

• You can now create synthetic events. This makes it much easier to work with
  ClientMessageEvents. For example:

  e = xcffib.xproto.ClientMessageEvent.synthetic(format=..., window=..., ...)
  conn.core.SendEvent(..., e.pack())
  

Why haskell?

Why is the binding generator written in haskell? Because haskell is awesome.

TODO

• XGE support? (xpyb doesn't implement this either)
• xprint and xkb support. These will require some non-trivial work in
  xcb-types, since it won't parse them correctly.