Bug 625484 - PyGobject does not know how to convert GType paramspec for class properties
Summary: PyGobject does not know how to convert GType paramspec for class properties
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Fedora
Classification: Fedora
Component: pygobject2
Version: 14
Hardware: All
OS: Linux
low
medium
Target Milestone: ---
Assignee: Colin Walters
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2010-08-19 15:21 UTC by Daniel Berrangé
Modified: 2012-08-16 21:20 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2012-08-16 21:20:27 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)
Special case GType conversion (1.20 KB, patch)
2010-09-05 16:55 UTC, Daniel Berrangé
no flags Details | Diff

Description Daniel Berrangé 2010-08-19 15:21:06 UTC
Description of problem:
I have a GObject subclass which registers a property called 'result-type' which accepts a GType as its value. At the C level it is declared with

    g_object_class_install_property(object_class,
                                    PROP_RESULT_TYPE,
                                    g_param_spec_gtype("result-type",
                                                       "Result type",
                                                       "The command result type",
                                                       G_TYPE_STRING,
                                                       G_PARAM_READABLE |
                                                       G_PARAM_WRITABLE |
                                                       G_PARAM_CONSTRUCT_ONLY |
                                                       G_PARAM_STATIC_NAME |
                                                       G_PARAM_STATIC_NICK |
                                                       G_PARAM_STATIC_BLURB));


Attempting it instantiate an instance of the class, in python, passing in the 'result-type' property value to the constructor:

        LibvirtShell.Command.__init__(self, name="foo", result_type=gobject.GObject.__gtype__)

fails with:

  Traceback (most recent call last):
    File "./plugins/pythonhello/pythonhello.py", line 36, in do_activate
      manager.add_command(MyCommand())
    File "./plugins/pythonhello/pythonhello.py", line 17, in __init__
      LibvirtShell.Command.__init__(self, name="foo", result_type=gobject.GObject.__gtype__)
  TypeError: could not convert value for property `result_type'


Python definitely knows that I am passing a GType instance:

       # print str(gobject.GObject.__gtype__)
       <GType GObject (80)>


Using set_property:

        self.set_property("result-type", gobject.GObject.__gtype__)

Gives a slightly different message:

Traceback (most recent call last):
  File "./plugins/pythonhello/pythonhello.py", line 36, in do_activate
    manager.add_command(MyCommand())
  File "./plugins/pythonhello/pythonhello.py", line 20, in __init__
    self.set_property("result-type", gobject.GObject.__gtype__)
TypeError: could not convert argument to correct param type



Version-Release number of selected component (if applicable):
pygobject2-2.21.5-3.fc14.x86_64

How reproducible:
Always for properties whose value is a GType

Steps to Reproduce:
1. See above example class property
2. Attempt to set the property from python
3.
  
Actual results:


Expected results:


Additional info:

Comment 1 Daniel Berrangé 2010-09-05 16:55:56 UTC
Created attachment 443173 [details]
Special case GType conversion

The problem methods are appear to be pyg_value_from_pyobject and pyg_value_to_pyobject, which don't handle G_TYPE_GTYPE correctly. G_TYPE_GTYPE inherits from G_TYPE_POINTER, but the case statement for G_TYPE_POINTER can't cope with G_TYPE_GTYPE data. This patch adds two special cases for G_TYPE_GTYPE.
I'm not sure this is the right way to approach it, but it makes it does seem to make things work for my app's needs.

Comment 2 Fedora End Of Life 2012-08-16 21:20:29 UTC
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