[Xcb] [PATCH proto 1/2] optionally enforce serialization of pads

[Christian Linhart]

>From now on, due to a patch in libxcb, pads will not be serialized
anymore. This is to maintain ABI-compatibility when adding
explicit align pads.

However, some align pads were already be serialized in prior
official versions of libxcb. Therefore we need a method to
enforce serialization, so we can maintainn ABI compatibility
with that legacy.

Signed-off-by: Christian Linhart <chris at demorecorder.com>
---
 doc/xml-xcb.txt  | 9 ++++++++-
 xcbgen/xtypes.py | 2 ++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/doc/xml-xcb.txt b/doc/xml-xcb.txt
index 12c0881..9cef1de 100644
--- a/doc/xml-xcb.txt
+++ b/doc/xml-xcb.txt
@@ -187,19 +187,26 @@ than type="PIXMAP".
 Note: Most of the below may optionally contain an enum, altenum, mask or altmask
 attribute, which follows the above rules for "type". "enum" is an exhaustive
 enum; the value is restricted to one of the constants named in the enum.
 "altenum" may be one of the values contained in the enum, but it need not be.
 "mask" refers to an exhaustive enum to be used as a bitmask.
 "altmask" may be a mask from the referred enum, but it need not be.
 
-<pad bytes="integer" />
+<pad bytes="integer" serialize="bool" />
 
   This element declares some padding in a data structure.  The bytes
   attribute declares the number of bytes of padding.
 
+  If serialize="true", then the pad will be serialized/deserialized.
+  This is only needed for ABI compatibility with legacy.
+  Newly added pads should not be defined with serialize="true".
+
+  The serialize attribute may be omitted.
+  Default is serialize="false".
+
 <field type="identifier" name="identifier" />
 
   This element represents a field in a data structure.  The type attribute
   declares the data type of the field, and the name attribute gives the name
   of the field.
 
 <fd name="identifier" />
diff --git a/xcbgen/xtypes.py b/xcbgen/xtypes.py
index 1f604de..c3b5758 100644
--- a/xcbgen/xtypes.py
+++ b/xcbgen/xtypes.py
@@ -2,14 +2,15 @@
 This module contains the classes which represent XCB data types.
 '''
 from xcbgen.expr import Field, Expression
 from xcbgen.align import Alignment, AlignmentLog
 import __main__
 
 verbose_align_log = False
+true_values = ['true', '1', 'yes']
 
 class Type(object):
     '''
     Abstract base class for all XCB data types.
     Contains default fields, and some abstract methods.
     '''
     def __init__(self, name):
@@ -425,14 +426,15 @@ class PadType(Type):
         self.is_pad = True
         self.size = 1
         self.nmemb = 1
         self.align = 1
         if elt != None:
             self.nmemb = int(elt.get('bytes', "1"), 0)
             self.align = int(elt.get('align', "1"), 0)
+            self.serialize = elt.get('serialize', "false").lower() in true_values
 
         # pads don't require any alignment at their start
         self.required_start_align = Alignment(1,0)
 
     def resolve(self, module):
         self.resolved = True
 
-- 
2.1.4