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A drop in replacement for xpyb, an XCB python binding

Project description

# xcffib [![Build Status](](

`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.

## 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
* `xcb.Request` is gone. It was an entirely internal and unnecessary interface.
* `xcffib.Connection.send_request` takes slightly different (but more sensible)
* 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 `` instead of
* As above, `void` is also packed/unpacked as `char`s, 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

## 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 `POINT`s 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 `POINT`s 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 synthtic events. This makes it much easier to work with
`ClientMessageEvent`s. 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.


* 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.

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