qtile: rework package

* Use absolute paths to load gobject, pango and cairo.
* Add xcb-cursor support (also with absolute path)
* Avoid tainting child processes environment:
  Save PATH and PYTHONPATH in wrapper, and restore them in python code.
* Alter restart process, using $0 saved in wrapper, which allow user
  to restart qtile after system rebuild to upgrade it.

pkgs/applications/window-managers/qtile/0001-Substitution-vars-for-absolute-paths.patch

@@ -0,0 +1,43 @@
+From 00c5af939567429d40877845dc52b54fde2d8a50 Mon Sep 17 00:00:00 2001
+From: "Alexander V. Nikolaev" <avn@avnik.info>
+Date: Thu, 26 Nov 2015 10:53:12 +0200
+Subject: [PATCH 1/3] Substitution vars for absolute paths
+
+---
+ libqtile/pangocffi.py | 6 +++---
+ libqtile/xcursors.py  | 2 +-
+ 2 files changed, 4 insertions(+), 4 deletions(-)
+
+diff --git a/libqtile/pangocffi.py b/libqtile/pangocffi.py
+index 27691d1..25f690d 100644
+--- a/libqtile/pangocffi.py
++++ b/libqtile/pangocffi.py
+@@ -58,9 +58,9 @@ except ImportError:
+     else:
+         raise ImportError("No module named libqtile._ffi_pango, be sure to run `python ./libqtile/ffi_build.py`")
+
+-gobject = ffi.dlopen('libgobject-2.0.so.0')
+-pango = ffi.dlopen('libpango-1.0.so.0')
+-pangocairo = ffi.dlopen('libpangocairo-1.0.so.0')
++gobject = ffi.dlopen('@glib@/lib/libgobject-2.0.so.0')
++pango = ffi.dlopen('@pango@/lib/libpango-1.0.so.0')
++pangocairo = ffi.dlopen('@pango@/lib/libpangocairo-1.0.so.0')
+
+
+ def CairoContext(cairo_t):
+diff --git a/libqtile/xcursors.py b/libqtile/xcursors.py
+index e0e55e1..59b6428 100644
+--- a/libqtile/xcursors.py
++++ b/libqtile/xcursors.py
+@@ -114,7 +114,7 @@ class Cursors(dict):
+
+     def _setup_xcursor_binding(self):
+         try:
+-            xcursor = ffi.dlopen('libxcb-cursor.so')
++            xcursor = ffi.dlopen('@xcb-cursor@/lib/libxcb-cursor.so')
+         except OSError:
+             self.log.warning("xcb-cursor not found, fallback to font pointer")
+             return False
+-- 
+2.6.3
+

pkgs/applications/window-managers/qtile/0002-Restore-PATH-and-PYTHONPATH.patch

@@ -0,0 +1,67 @@
+From f299a0aa0eefcf16bb4990f00ac3946727f43ef3 Mon Sep 17 00:00:00 2001
+From: "Alexander V. Nikolaev" <avn@avnik.info>
+Date: Fri, 27 Nov 2015 10:49:48 +0200
+Subject: [PATCH 2/3] Restore PATH and PYTHONPATH
+
+---
+ bin/qtile         | 1 +
+ bin/qtile-run     | 1 +
+ bin/qtile-session | 2 ++
+ libqtile/utils.py | 7 +++++++
+ 4 files changed, 11 insertions(+)
+
+diff --git a/bin/qtile b/bin/qtile
+index 66034fe..ce3fcd1 100755
+--- a/bin/qtile
++++ b/bin/qtile
+@@ -131,6 +131,7 @@ def make_qtile():
+
+
+ if __name__ == "__main__":
++    __import__("importlib").import_module("libqtile.utils").restore_os_environment()
+     rename_process()
+     q = make_qtile()
+     try:
+diff --git a/bin/qtile-run b/bin/qtile-run
+index ccedb96..646a476 100755
+--- a/bin/qtile-run
++++ b/bin/qtile-run
+@@ -50,6 +50,7 @@ def main():
+     proc.wait()
+
+ if __name__ == "__main__":
++    __import__("importlib").import_module("libqtile.utils").restore_os_environment()
+     try:
+         main()
+     except KeyboardInterrupt:
+diff --git a/bin/qtile-session b/bin/qtile-session
+index 84f6a2d..da31b12 100755
+--- a/bin/qtile-session
++++ b/bin/qtile-session
+@@ -25,6 +25,8 @@
+ Qtile session manager.
+ """
+
++__import__("importlib").import_module("libqtile.utils").restore_os_environment()
++
+ from libqtile.log_utils import init_log
+ import logging
+ import os
+diff --git a/libqtile/utils.py b/libqtile/utils.py
+index d5f975b..0fdb080 100644
+--- a/libqtile/utils.py
++++ b/libqtile/utils.py
+@@ -208,3 +208,10 @@ def get_cache_dir():
+     if not os.path.exists(cache_directory):
+         os.makedirs(cache_directory)
+     return cache_directory
++
++def restore_os_environment():
++    pythonpath = os.environ.pop("QTILE_SAVED_PYTHONPATH", "")
++    os.environ["PYTHONPATH"] = pythonpath
++    path = os.environ.pop("QTILE_SAVED_PATH", None)
++    if path:
++        os.environ["PATH"] = path
+-- 
+2.6.3
+

pkgs/applications/window-managers/qtile/0003-Restart-executable.patch

@@ -0,0 +1,25 @@
+From b560c11078fecc35df2c62f34beda06c4e80a10d Mon Sep 17 00:00:00 2001
+From: "Alexander V. Nikolaev" <avn@avnik.info>
+Date: Fri, 27 Nov 2015 10:54:35 +0200
+Subject: [PATCH 3/3] Restart executable
+
+---
+ libqtile/manager.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/libqtile/manager.py b/libqtile/manager.py
+index b1a38e2..110f7d8 100644
+--- a/libqtile/manager.py
++++ b/libqtile/manager.py
+@@ -1339,7 +1339,7 @@ class Qtile(command.CommandObject):
+         argv = [s for s in argv if not s.startswith('--with-state')]
+         argv.append('--with-state=' + buf.getvalue().decode())
+
+-        self.cmd_execute(sys.executable, argv)
++        self.cmd_execute(os.environ.get("QTILE_WRAPPER", "@out@/bin/qtile"), argv[1:])
+
+     def cmd_spawn(self, cmd):
+         """
+-- 
+2.6.3
+

pkgs/applications/window-managers/qtile/default.nix

@@ -1,5 +1,10 @@
 { stdenv, fetchFromGitHub, buildPythonPackage, python27Packages, pkgs }:
 
+let cairocffi-xcffib = python27Packages.cairocffi.override {
+    pythonPath = [ python27Packages.xcffib ];
+  };
+in
+
 buildPythonPackage rec {
   name = "qtile-${version}";
   version = "0.10.2";
@@ -11,29 +16,28 @@ buildPythonPackage rec {
     sha256 = "0dhdwjr4pdlzli68fa8glrnsjzxp6agdab9cnmpsqlwiwh97x9a6";
   };
 
-  patches = [ ./restart_executable.patch ];
+  patches = [
+    ./0001-Substitution-vars-for-absolute-paths.patch
+    ./0002-Restore-PATH-and-PYTHONPATH.patch
+    ./0003-Restart-executable.patch
+  ];
 
   postPatch = ''
     substituteInPlace libqtile/manager.py --subst-var-by out $out
+    substituteInPlace libqtile/pangocffi.py --subst-var-by glib ${pkgs.glib}
+    substituteInPlace libqtile/pangocffi.py --subst-var-by pango ${pkgs.pango}
+    substituteInPlace libqtile/xcursors.py --subst-var-by xcb-cursor ${pkgs.xorg.xcbutilcursor}
   '';
 
   buildInputs = [ pkgs.pkgconfig pkgs.glib pkgs.xorg.libxcb pkgs.cairo pkgs.pango python27Packages.xcffib ];
 
-  cairocffi-xcffib = python27Packages.cairocffi.override {
-    LD_LIBRARY_PATH = "${pkgs.xorg.libxcb}/lib:${pkgs.cairo}/lib";
-    pythonPath = [ python27Packages.xcffib ];
-  };
-
-  pythonPath = with python27Packages; [ xcffib cairocffi-xcffib trollius readline ];
-
-  LD_LIBRARY_PATH = "${pkgs.xorg.libxcb}/lib:${pkgs.cairo}/lib";
+  pythonPath = with python27Packages; [ xcffib cairocffi-xcffib trollius readline];
 
   postInstall = ''
     wrapProgram $out/bin/qtile \
-      --prefix LD_LIBRARY_PATH : ${pkgs.xorg.libxcb}/lib \
-      --prefix LD_LIBRARY_PATH : ${pkgs.glib}/lib \
-      --prefix LD_LIBRARY_PATH : ${pkgs.cairo}/lib \
-      --prefix LD_LIBRARY_PATH : ${pkgs.pango}/lib
+      --set QTILE_WRAPPER '"$0"' \
+      --set QTILE_SAVED_PYTHONPATH '"$PYTHONPATH"' \
+      --set QTILE_SAVED_PATH '"$PATH"'
   '';
 
   meta = with stdenv.lib; {