python wnck 在 pdb.set_trace() 之前不返回任何数据

Question

在Ubuntu Linux / Gnome系统上，我想用Python的wnck库来获取所有打开窗口的列表。

我的代码是这样的：

#! /usr/bin/python

from pprint import pprint
import wnck

screen = wnck.screen_get_default()

pprint(screen.get_windows())

import pdb ; pdb.set_trace()

pprint(screen.get_windows())

输出结果是这样的：

** (windowlist.py:4501): WARNING **: Trying to register gtype 'WnckWindowState' as enum when in fact it is of type 'GFlags'

** (windowlist.py:4501): WARNING **: Trying to register gtype 'WnckWindowActions' as enum when in fact it is of type 'GFlags'

** (windowlist.py:4501): WARNING **: Trying to register gtype 'WnckWindowMoveResizeMask' as enum when in fact it is of type 'GFlags'
[]
> /home/rory/personal/diriu/windowlist.py(12)<module>()
-> pprint(screen.get_windows())
(Pdb) c
[<wnck.Window object at 0xb61db0cc (WnckWindow at 0x992c000)>,
 <wnck.Window object at 0xb61db0f4 (WnckWindow at 0x992c0a8)>,
 <wnck.Window object at 0xb61db11c (WnckWindow at 0x992c150)>,
 <wnck.Window object at 0xb61db144 (WnckWindow at 0x992c1f8)>,
 <wnck.Window object at 0xb61db16c (WnckWindow at 0x992c2a0)>,
 <wnck.Window object at 0xb61db194 (WnckWindow at 0x992c348)>,
 <wnck.Window object at 0xb61db1bc (WnckWindow at 0x992c3f0)>,
 <wnck.Window object at 0xb61db1e4 (WnckWindow at 0x992c498)>,
 <wnck.Window object at 0xb61db20c (WnckWindow at 0x992c540)>,
 <wnck.Window object at 0xb61db234 (WnckWindow at 0x992c5e8)>,
 <wnck.Window object at 0xb61db25c (WnckWindow at 0x992c690)>,
 <wnck.Window object at 0xb61db284 (WnckWindow at 0x992c738)>]

第一次调用get_windows()时，返回的是[]，也就是一个空列表。第二次调用get_windows()时，返回的是打开窗口的列表。在pdb调试器里，我只按了c继续执行，没有做其他操作（在pdb里）。

如果我把pdb注释掉，那么两次调用get_windows()都会返回[]。如果在进入pdb之前多次调用get_windows()，也什么都得不到。如果在pdb之后多次调用get_windows()，我就会不断得到完整的窗口列表。

为什么这个调用在空的pdb之后才有效？我该怎么做才能在没有pdb的情况下也能正常工作？

Answer 1

我觉得这个问题和wnck没关系，但我想在使用pdb的时候，调用get_window的两次之间的时间应该足够让窗口列表初始化。你可以试着在调用get_window之前加个延迟，比如用sleep函数。

Answer 2

文件 so-wnck.py（来自 如何获取所有标题中包含特定词的窗口？）

import pygtk
pygtk.require('2.0')
import gtk
import wnck

screen = wnck.screen_get_default()
while gtk.events_pending():
    gtk.main_iteration()

windows = screen.get_windows()
print (windows)

python so-wnck.py

** (so-wnck.py:2367): WARNING **: Trying to register gtype 'WnckWindowState' as enum when in fact it is of type 'GFlags'

** (so-wnck.py:2367): WARNING **: Trying to register gtype 'WnckWindowActions' as enum when in fact it is of type 'GFlags'

** (so-wnck.py:2367): WARNING **: Trying to register gtype 'WnckWindowMoveResizeMask' as enum when in fact it is of type 'GFlags'
[<wnck.Window object at 0xb7566694 (WnckWindow at 0x97c51f8)>,
 <wnck.Window object at 0xb75666bc (WnckWindow at 0x97c52a0)>, 
 <wnck.Window object at 0xb75666e4 (WnckWindow at 0x97c5348)>, 
 <wnck.Window object at 0xb756670c (WnckWindow at 0x97c53f0)>, 
 <wnck.Window object at 0xb7566734 (WnckWindow at 0x97c5498)>,
 <wnck.Window object at 0xb756675c (WnckWindow at 0x97c5540)>, 
 <wnck.Window object at 0xb7566784 (WnckWindow at 0x97c55e8)>]