1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
|
<HTML
><HEAD
><TITLE
>General Limitations</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="Python Bindings for KDE (PyKDE-3.16.0)"
HREF="index.html"><LINK
REL="PREVIOUS"
TITLE="Python Bindings for KDE (PyKDE-3.16.0)"
HREF="index.html"><LINK
REL="NEXT"
TITLE="Signal and Slot Support"
HREF="signal.html"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>Python Bindings for KDE (PyKDE-3.3.16.0)</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="dcopext.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="signal.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN28"
></A
>General Limitations</H1
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN30"
></A
>Python Strings, TQt Strings and Unicode</H2
><P
>Unicode support was added to TQt in v2.0 and to Python in v1.6. In TQt, Unicode
support is implemented using the <TT
CLASS="LITERAL"
>TQString</TT
> class. It is
important to understand that <TT
CLASS="LITERAL"
>TQString</TT
>s, Python string objects
and Python Unicode objects are all different but conversions between them are
automatic in many cases and easy to achieve manually when needed.</P
><P
>Whenever PyKDE expects a <TT
CLASS="LITERAL"
>TQString</TT
> as a function argument, a
Python string object or a Python Unicode object can be provided instead, and
PyKDE will do the necessary conversion automatically.</P
><P
>You may also manually convert Python string and Unicode objects to
<TT
CLASS="LITERAL"
>TQString</TT
>s by using the <TT
CLASS="LITERAL"
>TQString</TT
> constructor
as demonstrated in the following code fragment.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>qs1 = TQString('Converted Python string object')
qs2 = TQString(u'Converted Python Unicode object')</PRE
></TD
></TR
></TABLE
><P
>In order to convert a <TT
CLASS="LITERAL"
>TQString</TT
> to a Python string object use
the Python <TT
CLASS="LITERAL"
>str()</TT
> function. Applying
<TT
CLASS="LITERAL"
>str()</TT
> to a null <TT
CLASS="LITERAL"
>TQString</TT
> and an empty
<TT
CLASS="LITERAL"
>TQString</TT
> both result in an empty Python string object.</P
><P
>In order to convert a <TT
CLASS="LITERAL"
>TQString</TT
> to a Python Unicode object use
the Python <TT
CLASS="LITERAL"
>unicode()</TT
> function. Applying
<TT
CLASS="LITERAL"
>unicode()</TT
> to a null <TT
CLASS="LITERAL"
>TQString</TT
> and an empty
<TT
CLASS="LITERAL"
>TQString</TT
> both result in an empty Python Unicode object.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN53"
></A
>Access to Protected Member Functions</H2
><P
>When an instance of a C++ class is not created from Python it is not possible
to access the protected member functions, or emit the signals, of that
instance. Attempts to do so will raise a Python exception. Also, any Python
methods corresponding to the instance's virtual member functions will never be
called.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN56"
></A
>Garbage Collection</H2
><P
>C++ does not garbage collect unreferenced class instances, whereas Python does.
In the following C++ fragment both colours exist even though the first can no
longer be referenced from within the program:</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>c = TQColor();
c = TQColor();</PRE
></TD
></TR
></TABLE
><P
>In the corresponding Python fragment, the first colour is destroyed when
the second is assigned to <TT
CLASS="LITERAL"
>c</TT
>:</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>c = TQColor()
c = TQColor()</PRE
></TD
></TR
></TABLE
><P
>In Python, each colour must be assigned to different names. Typically this
is done within class definitions, so the code fragment would be something like:</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>self.c1 = TQColor()
self.c2 = TQColor()</PRE
></TD
></TR
></TABLE
><P
>Sometimes a TQt class instance will maintain a pointer to another instance and
will eventually call the destructor of that second instance. The most common
example is that a <TT
CLASS="LITERAL"
>TQObject</TT
> (and any of its sub-classes) keeps
pointers to its children and will automatically call their destructors. In
these cases, the corresponding Python object will also keep a reference to the
corresponding child objects.</P
><P
>So, in the following Python fragment, the first <TT
CLASS="LITERAL"
>TQLabel</TT
> is
not destroyed when the second is assigned to <TT
CLASS="LITERAL"
>l</TT
> because the
parent <TT
CLASS="LITERAL"
>TQWidget</TT
> still has a reference to it.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>p = TQWidget()
l = TQLabel('First label',p)
l = TQLabel('Second label',p)</PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN72"
></A
>C++ Variables</H2
><P
>Access to C++ variables is supported. They are accessed as Python instance
variables. For example:</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>tab = TQTab()
tab.label = "First Tab"
tab.r = TQRect(10,10,75,30)</PRE
></TD
></TR
></TABLE
><P
>Global variables and static class variables are effectively read-only. They
can be assigned to, but the underlying C++ variable will not be changed. This
may change in the future.</P
><P
>Access to protected C++ class variables is not supported. This may change in
the future.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN78"
></A
>Multiple Inheritance</H2
><P
>It is not possible to define a new Python class that sub-classes from more than
one TQt class.</P
></DIV
></DIV>
<H2 CLASS="SECT2">tr() methods</H2>
<P>
In a normal TQt installation, every descendant of TQObject inherits two methods
(tr (const char *) and tr (const char *, const char *) from TQObject explicitly
and also overloads these methods via the moc mechanism (by defining Q_OBJECT
in the class declaration). KDE however is compiled with -DQT_NO_TRANSLATION,
which prevents moc from creating the overloading tr() methods, and also produces
side-effects with a normal TQt installation which was compiled without the
-DQT_NO_TRANSLATION switch.
</P>
<P>
PyKDE handles this situation by NOT providing tr() methods (either the inherited
methods from TQObject or the moc generated methods) for any KDE based TQObject
descendant. The tr() methods are static, so TQObject::tr () methods are available
via PyTQt, as are tr() methods for any PyTQt TQObject descendant. PyKDE's handling
of these methods has no effect on PyTQt.
</P>
<P>Instead of the tr() methods, KDE uses corresponding i18n() methods for translating.
These methods are available in the tdecore module of PyKDE. For compatibility with
KDE, you should use the i18n methods.
</P>
<H2>Socket classes</H2>
<P>
The following classes (introduced in KDE2.2.0) are NOT yet implemented:
</P>
<TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%">
<TR>
<TD>
<PRE CLASS="PROGRAMLISTING">
KAddressInfo
KExtendedSocket
KInetSocketAddress
TDESocketAddress
KUnixSocketAddress
KSocks
</PRE>
</TD>
</TR>
</TABLE>
<P>
Most of their functionality already exists in the Python socket class or in the
TDESocket class (tdecore module). These classes may be implemented at a future date
(they require support for C socket structures and careful handling to avoid buffer
overflow problems/exploits)
</P>
<DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="dcopext.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="signal.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>DCOP and Extensions</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
> </TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Signal and Slot Support</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
|
