1 \chapter{Introduction
}\label{introduction
}
2 \pagenumbering{arabic
}%
3 \setheader{{\it CHAPTER
\thechapter}}{}{}{}{}{{\it CHAPTER
\thechapter}}%
4 \setfooter{\thepage}{}{}{}{}{\thepage}%
6 \section{What is wxWidgets?
}\label{whatis
}
8 wxWidgets is a C++ framework providing GUI (Graphical User
9 Interface) and other facilities on more than one platform. Version
2 currently
10 supports all desktop versions of MS Windows, Unix with GTK+, Unix with Motif,
11 and MacOS. An OS/
2 port is in progress.
13 wxWidgets was originally developed at the Artificial Intelligence
14 Applications Institute, University of Edinburgh, for internal use,
15 and was first made publicly available in
1992.
16 Version
2 is a vastly improved version written and maintained by
17 Julian Smart, Robert Roebling, Vadim Zeitlin, Vaclav Slavik and many others.
19 This manual contains a class reference and topic overviews.
20 For a selection of wxWidgets tutorials, please see the documentation page on the
\urlref{wxWidgets web site
}{http://www.wxwidgets.org
}.
22 Please note that in the following, ``MS Windows" often refers to all
23 platforms related to Microsoft Windows, including
16-bit and
32-bit
24 variants, unless otherwise stated. All trademarks are acknowledged.
26 \section{Why another cross-platform development tool?
}\label{why
}
28 wxWidgets was developed to provide a cheap and flexible way to maximize
29 investment in GUI application development. While a number of commercial
30 class libraries already existed for cross-platform development,
31 none met all of the following criteria:
33 \begin{enumerate
}\itemsep=
0pt
35 \item source availability;
36 \item simplicity of programming;
37 \item support for a wide range of compilers.
40 Since wxWidgets was started, several other free or almost-free
41 GUI frameworks have emerged. However, none has the range of
42 features, flexibility, documentation and the well-established
43 development team that wxWidgets has.
45 As open source software, wxWidgets has benefited from comments,
46 ideas, bug fixes, enhancements and the sheer enthusiasm of
47 users. This gives wxWidgets a certain advantage over its
48 commercial competitors (and over free libraries without an
49 independent development team), plus a robustness against the
50 transience of one individual or company. This openness and
51 availability of source code is especially important when the
52 future of thousands of lines of application code may depend upon
53 the longevity of the underlying class library.
55 Version
2 goes much further than previous versions in terms of
56 generality and features, allowing applications to be produced
57 that are often indistinguishable from those produced using
58 single-platform toolkits such as Motif, GTK+ and MFC.
60 The importance of using a platform-independent class library
61 cannot be overstated, since GUI application development is very
62 time-consuming, and sustained popularity of particular GUIs
63 cannot be guaranteed. Code can very quickly become obsolete if
64 it addresses the wrong platform or audience. wxWidgets helps to
65 insulate the programmer from these winds of change. Although
66 wxWidgets may not be suitable for every application (such as an
67 OLE-intensive program), it provides access to most of the
68 functionality a GUI program normally requires, plus many extras
69 such as network programming, PostScript output, and HTML
70 rendering; and it can of course be extended as needs dictate.
71 As a bonus, it provides a far cleaner and easier programming
72 interface than the native APIs. Programmers may find it
73 worthwhile to use wxWidgets even if they are developing on only
76 It is impossible to sum up the functionality of wxWidgets in a few paragraphs, but
77 here are some of the benefits:
79 \begin{itemize
}\itemsep=
0pt
80 \item Low cost (free, in fact!)
81 \item You get the source.
82 \item Available on a variety of popular platforms.
83 \item Works with almost all popular C++ compilers and Python.
84 \item Over
50 example programs.
85 \item Over
1000 pages of printable and on-line documentation.
86 \item Includes Tex2RTF, to allow you to produce your own documentation
87 in Windows Help, HTML and Word RTF formats.
88 \item Simple-to-use, object-oriented API.
89 \item Flexible event system.
90 \item Graphics calls include lines, rounded rectangles, splines, polylines, etc.
91 \item Constraint-based and sizer-based layouts.
92 \item Print/preview and
document/view architectures.
93 \item Toolbar, notebook, tree control, advanced list control classes.
94 \item PostScript generation under Unix, normal MS Windows printing on the PC.
95 \item MDI (Multiple Document Interface) support.
96 \item Can be used to create DLLs under Windows, dynamic libraries on Unix.
97 \item Common dialogs for file browsing, printing, colour selection, etc.
98 \item Under MS Windows, support for creating metafiles and copying
99 them to the clipboard.
100 \item An API for invoking help from applications.
101 \item Ready-to-use HTML window (supporting a subset of HTML).
102 \item Network support via a family of socket and protocol classes.
103 \item Support for platform independent image processing.
104 \item Built-in support for many file formats (BMP, PNG, JPEG, GIF, XPM, PNM, PCX).
108 \section{Changes from version
2.0}\label{versionchanges20
}
110 These are a few of the differences between versions
2.0 and
2.2.
114 \begin{itemize
}\itemsep=
0pt
115 \item GTK
1.0 no longer supported.
118 Additions and changes:
120 \begin{itemize
}\itemsep=
0pt
121 \item Corrected many classes to conform better to documented behaviour.
122 \item Added handlers for more image formats (Now GIF, JPEG, PCX, BMP, XPM, PNG, PNM).
123 \item Improved support for socket and network functions.
124 \item Support for different national font encodings.
125 \item Sizer based layout system.
126 \item HTML widget and help system.
127 \item Added some controls (e.g. wxSpinCtrl) and supplemented many.
128 \item Many optical improvements to GTK port.
129 \item Support for menu accelerators in GTK port.
130 \item Enhanced and improved support for scrolling, including child windows.
131 \item Complete rewrite of clipboard and drag and drop classes.
132 \item Improved support for ODBC databases.
133 \item Improved tab traversal in dialogs.
137 \section{wxWidgets requirements
}\label{requirements
}
139 To make use of wxWidgets, you currently need one of the following setups.
143 \begin{enumerate
}\itemsep=
0pt
144 \item A
32-bit or
64-bit PC running MS Windows.
145 \item A Windows compiler: MS Visual C++ (embedded Visual C++ for wxWinCE
146 port), Borland C++, Watcom C++, Cygwin, MinGW, Metrowerks CodeWarrior,
147 Digital Mars C++. See
{\tt install.txt
} for details about compiler
149 \item At least
100 MB of disk space for source tree and additional space for
150 libraries and application building (depends on compiler and build settings).
155 \begin{enumerate
}\itemsep=
0pt
156 \item Almost any C++ compiler, including GNU C++ (EGCS
1.1.1 or above).
157 \item Almost any Unix workstation, and one of: GTK+
1.2, GTK+
2.0, Motif
1.2 or higher, Lesstif.
158 If using the wxX11 port, no such widget set is required.
159 \item At least
100 MB of disk space for source tree and additional space for
160 libraries and application building (depends on compiler and build settings).
165 \begin{enumerate
}\itemsep=
0pt
166 \item A PowerPC Mac running Mac OS
8.6/
9.x (eg. Classic) or Mac OS X
10.x.
167 \item CodeWarrior
5.3,
6 or
7 for Classic Mac OS.
168 \item The Apple Developer Tools (eg. GNU C++), CodeWarrior
7 or above for Mac OS X.
169 \item At least
100 MB of disk space for source tree and additional space for
170 libraries and application building (depends on compiler and build settings).
173 \section{Availability and location of wxWidgets
}\label{where
}
175 \winhelponly{wxWidgets is available by anonymous FTP and World Wide Web
176 from ftp://biolpc22.york.ac.uk/pub and/or http://www.wxwidgets.org.
}
177 \winhelpignore{wxWidgets is available by anonymous FTP and World Wide Web
178 from
\urlref{ftp://biolpc22.york.ac.uk/pub
}{ftp://biolpc22.york.ac.uk/pub
}
179 and/or
\urlref{http://www.wxwidgets.org
}{http://www.wxwidgets.org
}.
}
181 You can also buy a CD-ROM using the form on the Web site.
183 \section{Acknowledgements
}\label{acknowledgements
}
185 Thanks are due to AIAI for being willing to release the original version of
186 wxWidgets into the public domain, and to our patient partners.
188 We would particularly like to thank the following for their contributions to wxWidgets, and the many others who have been involved in
189 the project over the years. Apologies for any unintentional omissions from this list.
191 Yiorgos Adamopoulos, Jamshid Afshar, Alejandro Aguilar-Sierra, AIAI,
192 Patrick Albert, Karsten Ballueder, Mattia Barbon, Michael Bedward,
193 Kai Bendorf, Yura Bidus, Keith Gary Boyce, Chris Breeze, Pete Britton,
194 Ian Brown, C. Buckley, Marco Cavallini, Dmitri Chubraev, Robin Corbet, Cecil Coupe,
195 Stefan Csomor, Andrew Davison, Gilles Depeyrot, Neil Dudman, Robin Dunn,
196 Hermann Dunkel, Jos van Eijndhoven, Chris Elliott, David Elliott, Tom Felici,
197 Thomas Fettig, Matthew Flatt, Pasquale Foggia, Josep Fortiana, Todd Fries,
198 Dominic Gallagher, Guillermo Rodriguez Garcia, Wolfram Gloger, Norbert Grotz,
199 Stefan Gunter, Bill Hale, Patrick Halke, Stefan Hammes, Guillaume Helle,
200 Harco de Hilster, Kevin Hock, Cord Hockemeyer, Markus Holzem, Olaf Klein, Leif Jensen,
201 Bart Jourquin, Guilhem Lavaux, Ron Lee, Jan Lessner, Nicholas Liebmann,
202 Torsten Liermann, Per Lindqvist, Thomas Runge, Tatu M\"
{a
}nnist\"
{o
},
203 Scott Maxwell, Thomas Myers, Oliver Niedung, Stefan Neis, Ryan Norton, Hernan Otero,
204 Ian Perrigo, Timothy Peters, Giordano Pezzoli, Harri Pasanen, Thomaso Paoletti,
205 Garrett Potts, Marcel Rasche, Robert Roebling, Dino Scaringella,
206 Jobst Schmalenbach, Arthur Seaton, Paul Shirley, Wlodzimierz `ABX' Skiba,
207 Vaclav Slavik, Julian Smart, Stein Somers, Petr Smilauer, Neil Smith,
208 Kari Syst\"
{a
}, George Tasker, Arthur Tetzlaff-Deas, Jonathan Tonberg,
209 Jyrki Tuomi, Janos Vegh, Andrea Venturoli, David Webster, Otto Wyss,
210 Vadim Zeitlin, Xiaokun Zhu, Edward Zimmermann.
212 `Graphplace', the basis for the wxGraphLayout library, is copyright Dr. Jos
213 T.J. van Eijndhoven of Eindhoven University of Technology. The code has
214 been used in wxGraphLayout with his permission.
216 We also acknowledge the author of XFIG, the excellent Unix drawing tool,
217 from the source of which we have borrowed some spline drawing code.
218 His copyright is included below.
220 {\it XFig2.1 is copyright (c)
1985 by Supoj Sutanthavibul. Permission to
221 use, copy, modify, distribute, and sell this software and its
222 documentation for any purpose is hereby granted without fee, provided
223 that the above copyright notice appear in all copies and that both that
224 copyright notice and this permission notice appear in supporting
225 documentation, and that the name of M.I.T. not be used in advertising or
226 publicity pertaining to distribution of the software without specific,
227 written prior permission. M.I.T. makes no representations about the
228 suitability of this software for any purpose. It is provided ``as is''
229 without express or implied warranty.
}
231 \chapter{Multi-platform development with wxWidgets
}\label{multiplat
}
232 \setheader{{\it CHAPTER
\thechapter}}{}{}{}{}{{\it CHAPTER
\thechapter}}%
233 \setfooter{\thepage}{}{}{}{}{\thepage}%
235 This chapter describes the practical details of using wxWidgets. Please
236 see the file install.txt for up-to-date installation instructions, and
237 changes.txt for differences between versions.
239 \section{Include files
}\label{includefiles
}
241 The main include file is
{\tt "wx/wx.h"
}; this includes the most commonly
242 used modules of wxWidgets.
244 To save on compilation time, include only those header files relevant to the
245 source file. If you are using precompiled headers, you should include
246 the following section before any other includes:
249 // For compilers that support precompilation, includes "wx.h".
250 #include <wx/wxprec.h>
257 // Include your minimal set of headers here, or wx.h
261 ... now your other include files ...
264 The file
{\tt "wx/wxprec.h"
} includes
{\tt "wx/wx.h"
}. Although this incantation
265 may seem quirky, it is in fact the end result of a lot of experimentation,
266 and several Windows compilers to use precompilation which is largely automatic for
267 compilers with necessary support. Currently it is used for Visual C++ (including
268 embedded Visual C++), Borland C++, Open Watcom C++ and newer versions of GCC.
269 Some compilers might need extra work from the application developer to set the
270 build environment up as necessary for the support.
272 \section{Libraries
}\label{libraries
}
274 Most ports of wxWidgets can create either a static library or a shared
275 library. wxWidgets can also be built in multilib and monolithic variants.
276 See the
\helpref{libraries list
}{librarieslist
} for more
277 information on these.
279 \section{Configuration
}\label{configuration
}
281 When using project files and makefiles directly to build wxWidgets,
282 options are configurable in the file
283 \rtfsp{\tt "wx/XXX/setup.h"
} where XXX is the required platform (such as msw, motif, gtk, mac). Some
284 settings are a matter of taste, some help with platform-specific problems, and
285 others can be set to minimize the size of the library. Please see the setup.h file
286 and
{\tt install.txt
} files for details on configuration.
288 When using the 'configure' script to configure wxWidgets (on Unix and other platforms where
289 configure is available), the corresponding setup.h files are generated automatically
290 along with suitable makefiles. When using the RPM packages
291 for installing wxWidgets on Linux, a correct setup.h is shipped in the package and
292 this must not be changed.
294 \section{Makefiles
}\label{makefiles
}
296 On Microsoft Windows, wxWidgets has a different set of makefiles for each
297 compiler, because each compiler's 'make' tool is slightly different.
298 Popular Windows compilers that we cater for, and the corresponding makefile
299 extensions, include: Microsoft Visual C++ (.vc), Borland C++ (.bcc),
300 OpenWatcom C++ (.wat) and MinGW/Cygwin (.gcc). Makefiles are provided
301 for the wxWidgets library itself, samples, demos, and utilities.
303 On Linux, Mac and OS/
2, you use the 'configure' command to
304 generate the necessary makefiles. You should also use this method when
305 building with MinGW/Cygwin on Windows.
307 We also provide project files for some compilers, such as
308 Microsoft VC++. However, we recommend using makefiles
309 to build the wxWidgets library itself, because makefiles
310 can be more powerful and less manual intervention is required.
312 On Windows using a compiler other than MinGW/Cygwin, you would
313 build the wxWidgets library from the build/msw directory
314 which contains the relevant makefiles.
316 On Windows using MinGW/Cygwin, and on Unix, MacOS X and OS/
2, you invoke
317 'configure' (found in the top-level of the wxWidgets source hierarchy),
318 from within a suitable empty directory for containing makefiles, object files and
321 For details on using makefiles, configure, and project files,
322 please see docs/xxx/install.txt in your distribution, where
323 xxx is the platform of interest, such as msw, gtk, x11, mac.
325 \section{Windows-specific files
}\label{windowsfiles
}
327 wxWidgets application compilation under MS Windows requires at least one
328 extra file: a resource file.
330 \subsection{Resource file
}\label{resources
}
332 The least that must be defined in the Windows resource file (extension RC)
333 is the following statement:
336 #include "wx/msw/wx.rc"
339 which includes essential internal wxWidgets definitions. The resource script
340 may also contain references to icons, cursors, etc., for example:
346 The icon can then be referenced by name when creating a frame icon. See
347 the MS Windows SDK documentation.
349 \normalbox{Note: include wx.rc
{\it after
} any ICON statements
350 so programs that search your executable for icons (such
351 as the Program Manager) find your application icon first.
}
353 \section{Allocating and deleting wxWidgets objects
}\label{allocatingobjects
}
355 In general, classes derived from wxWindow must dynamically allocated
356 with
{\it new
} and deleted with
{\it delete
}. If you delete a window,
357 all of its children and descendants will be automatically deleted,
358 so you don't need to delete these descendants explicitly.
360 When deleting a frame or dialog, use
{\bf Destroy
} rather than
{\bf delete
} so
361 that the wxWidgets delayed deletion can take effect. This waits until idle time
362 (when all messages have been processed) to actually delete the window, to avoid
363 problems associated with the GUI sending events to deleted windows.
365 Don't create a window on the stack, because this will interfere
366 with delayed deletion.
368 If you decide to allocate a C++ array of objects (such as wxBitmap) that may
369 be cleaned up by wxWidgets, make sure you delete the array explicitly
370 before wxWidgets has a chance to do so on exit, since calling
{\it delete
} on
371 array members will cause memory problems.
373 wxColour can be created statically: it is not automatically cleaned
374 up and is unlikely to be shared between other objects; it is lightweight
375 enough for copies to be made.
377 Beware of deleting objects such as a wxPen or wxBitmap if they are still in use.
378 Windows is particularly sensitive to this: so make sure you
379 make calls like wxDC::SetPen(wxNullPen) or wxDC::SelectObject(wxNullBitmap) before deleting
380 a drawing object that may be in use. Code that doesn't do this will probably work
381 fine on some platforms, and then fail under Windows.
383 \section{Architecture dependency
}\label{architecturedependency
}
385 A problem which sometimes arises from writing multi-platform programs is that
386 the basic C types are not defined the same on all platforms. This holds true
387 for both the length in bits of the standard types (such as int and long) as
388 well as their byte order, which might be little endian (typically
389 on Intel computers) or big endian (typically on some Unix workstations). wxWidgets
390 defines types and macros that make it easy to write architecture independent
393 wxInt32, wxInt16, wxInt8, wxUint32, wxUint16 = wxWord, wxUint8 = wxByte
395 where wxInt32 stands for a
32-bit signed integer type etc. You can also check
396 which architecture the program is compiled on using the wxBYTE
\_ORDER define
397 which is either wxBIG
\_ENDIAN or wxLITTLE
\_ENDIAN (in the future maybe wxPDP
\_ENDIAN
400 The macros handling bit-swapping with respect to the applications endianness
401 are described in the
\helpref{Byte order macros
}{byteordermacros
} section.
403 \section{Conditional compilation
}\label{conditionalcompilation
}
405 One of the purposes of wxWidgets is to reduce the need for conditional
406 compilation in source code, which can be messy and confusing to follow.
407 However, sometimes it is necessary to incorporate platform-specific
408 features (such as metafile use under MS Windows). The symbols
409 listed in the file
{\tt symbols.txt
} may be used for this purpose,
410 along with any user-supplied ones.
412 \section{C++ issues
}\label{cpp
}
414 The following documents some miscellaneous C++ issues.
416 \subsection{Templates
}\label{templates
}
418 wxWidgets does not use templates (except for some advanced features that
419 are switched off by default) since it is a notoriously unportable feature.
421 \subsection{RTTI
}\label{rtti
}
423 wxWidgets does not use C++ run-time type information since wxWidgets provides
424 its own run-time type information system, implemented using macros.
426 \subsection{Type of NULL
}\label{null
}
428 Some compilers (e.g. the native IRIX cc) define NULL to be
0L so that
429 no conversion to pointers is allowed. Because of that, all these
430 occurrences of NULL in the GTK+ port use an explicit conversion such
435 wxWindow *my_window = (wxWindow*) NULL;
439 It is recommended to adhere to this in all code using wxWidgets as
440 this make the code (a bit) more portable.
442 \subsection{Precompiled headers
}\label{precompiledheaders
}
444 Some compilers, such as Borland C++ and Microsoft C++, support
445 precompiled headers. This can save a great deal of compiling time. The
446 recommended approach is to precompile
{\tt "wx.h"
}, using this
447 precompiled header for compiling both wxWidgets itself and any
448 wxWidgets applications. For Windows compilers, two dummy source files
449 are provided (one for normal applications and one for creating DLLs)
450 to allow initial creation of the precompiled header.
452 However, there are several downsides to using precompiled headers. One
453 is that to take advantage of the facility, you often need to include
454 more header files than would normally be the case. This means that
455 changing a header file will cause more recompilations (in the case of
456 wxWidgets, everything needs to be recompiled since everything includes
{\tt "wx.h"
}!)
458 A related problem is that for compilers that don't have precompiled
459 headers, including a lot of header files slows down compilation
460 considerably. For this reason, you will find (in the common
461 X and Windows parts of the library) conditional
462 compilation that under Unix, includes a minimal set of headers;
463 and when using Visual C++, includes
{\tt wx.h
}. This should help provide
464 the optimal compilation for each compiler, although it is
465 biased towards the precompiled headers facility available
468 \section{File handling
}\label{filehandling
}
470 When building an application which may be used under different
471 environments, one difficulty is coping with documents which may be
472 moved to different directories on other machines. Saving a file which
473 has pointers to full pathnames is going to be inherently unportable. One
474 approach is to store filenames on their own, with no directory
475 information. The application searches through a number of locally
476 defined directories to find the file. To support this, the class
{\bf
477 wxPathList
} makes adding directories and searching for files easy, and
478 the global function
{\bf wxFileNameFromPath
} allows the application to
479 strip off the filename from the path if the filename must be stored.
480 This has undesirable ramifications for people who have documents of the
481 same name in different directories.
483 As regards the limitations of DOS
8+
3 single-case filenames versus
484 unrestricted Unix filenames, the best solution is to use DOS filenames
485 for your application, and also for
document filenames
{\it if
} the user
486 is likely to be switching platforms regularly. Obviously this latter
487 choice is up to the application user to decide. Some programs (such as
488 YACC and LEX) generate filenames incompatible with DOS; the best
489 solution here is to have your Unix makefile rename the generated files
490 to something more compatible before transferring the source to DOS.
491 Transferring DOS files to Unix is no problem, of course, apart from EOL
492 conversion for which there should be a utility available (such as
495 See also the File Functions section of the reference manual for
496 descriptions of miscellaneous file handling functions.
498 \chapter{Utilities and libraries supplied with wxWidgets
}\label{utilities
}
499 \setheader{{\it CHAPTER
\thechapter}}{}{}{}{}{{\it CHAPTER
\thechapter}}%
500 \setfooter{\thepage}{}{}{}{}{\thepage}%
502 In addition to the core wxWidgets library, a number of further
503 libraries and utilities are supplied with each distribution.
505 Some are under the 'contrib' hierarchy which mirrors the
506 structure of the main wxWidgets hierarchy. See also the 'utils'
507 hierarchy. The first place to look for documentation about
508 these tools and libraries is under the wxWidgets 'docs' hierarchy,
509 for example
{\tt docs/htmlhelp/fl.chm
}.
511 For other user-contributed packages, please see the Contributions page
512 on the
\urlref{wxWidgets Web site
}{http://www.wxwidgets.org
}.
514 \begin{description
}\itemsep=
0pt
515 \item[{\bf Helpview
}]
516 Helpview is a program for displaying wxWidgets HTML
517 Help files. In many cases, you may wish to use the wxWidgets HTML
518 Help classes from within your application, but this provides a
519 handy stand-alone viewer. See
\helpref{wxHTML Notes
}{wxhtml
} for more details.
520 You can find it in
{\tt samples/html/helpview
}.
522 Supplied with wxWidgets is a utility called Tex2RTF for converting
\rtfsp
523 \LaTeX\ manuals HTML, MS HTML Help, wxHTML Help, RTF, and Windows
524 Help RTF formats. Tex2RTF is used for the wxWidgets manuals and can be used independently
525 by authors wishing to create on-line and printed manuals from the same
\rtfsp
526 \LaTeX\ source. Please see the separate documentation for Tex2RTF.
527 You can find it under
{\tt utils/tex2rtf
}.
529 Helpgen takes C++ header files and generates a Tex2RTF-compatible
530 documentation file for each class it finds, using comments as appropriate.
531 This is a good way to start a reference for a set of classes.
532 Helpgen can be found in
{\tt utils/HelpGen
}.
533 \item[{\bf Emulator
}]
534 Xnest-based display emulator for X11-based PDA applications. On some
535 systems, the Xnest window does not synchronise with the
536 'skin' window. This program can be found in
{\tt utils/emulator
}.
537 \item[{\bf Configuration Tool
}]
538 The wxWidgets Configuration Tool is a work in progress
539 intended to make it easier to configure wxWidgets
540 features in detail. It exports setup.h configurations and will
541 eventually generate makefile config files. Invoking compilers is
542 also on the cards. Since configurations are
543 handled one at a time, the tool is of limited used until further
544 development can be done. The program can be found in
{\tt utils/configtool
}.
545 \item[{\bf XRC resource system
}]
546 This is the sizer-aware resource system, and uses
547 XML-based resource specifications that can be generated by tools
548 such as
\urlref{wxDesigner
}{http://www.roebling.de
}.
549 You can find this in
{\tt src/xrc
},
{\tt include/wx/xrc
},
{\tt samples/xrc
}.
550 For more information, see the
\helpref{XML-based resource system overview
}{xrcoverview
}.
551 \item[{\bf Object Graphics Library
}]
552 OGL defines an API for applications that need to display objects connected by lines.
553 The objects can be moved around and interacted with.
554 You can find this in
{\tt contrib/src/ogl
},
{\tt contrib/include/wx/ogl
}, and
{\tt contrib/samples/ogl
}.
555 \item[{\bf Frame Layout library
}]
556 FL provides sophisticated pane dragging and docking facilities.
557 You can find this in
{\tt contrib/src/fl
},
{\tt contrib/include/wx/fl
}, and
{\tt contrib/samples/fl
}.
558 \item[{\bf Gizmos library
}]
559 Gizmos is a collection of useful widgets and other classes. Classes include wxLEDNumberCtrl,
560 wxEditableListBox, wxMultiCellCanvas.
561 You can find this in
{\tt contrib/src/gizmos
},
{\tt contrib/include/wx/gizmos
}, and
{\tt contrib/samples/gizmos
}.
562 \item[{\bf Net library
}]
563 Net is a collection of very simple mail and web related classes. Currently
564 there is only wxEmail, which makes it easy to send email messages via MAPI on Windows or sendmail on Unix.
565 You can find this in
{\tt contrib/src/net
} and
{\tt contrib/include/wx/net
}.
566 \item[{\bf Animate library
}]
567 Animate allows you to load animated GIFs and play them on a window. The library can be extended
568 to use other animation formats.
569 You can find this in
{\tt contrib/src/animate
},
{\tt contrib/include/wx/animate
}, and
{\tt contrib/samples/animate
}.
570 \item[{\bf MMedia library
}]
571 Mmedia supports a variety of multimedia functionality. The status of this library is currently unclear.
572 You can find this in
{\tt contrib/src/mmedia
},
{\tt contrib/include/wx/mmedia
}, and
{\tt contrib/samples/mmedia
}.
573 \item[{\bf Styled Text Control library
}]
574 STC is a wrapper around Scintilla, a syntax-highlighting text editor.
575 You can find this in
{\tt contrib/src/stc
},
{\tt contrib/include/wx/stc
}, and
{\tt contrib/samples/stc
}.
577 Plot is a simple curve plotting library.
578 You can find this in
{\tt contrib/src/plot
},
{\tt contrib/include/wx/plot
}, and
{\tt contrib/samples/plot
}.
581 \chapter{Programming strategies
}\label{strategies
}
582 \setheader{{\it CHAPTER
\thechapter}}{}{}{}{}{{\it CHAPTER
\thechapter}}%
583 \setfooter{\thepage}{}{}{}{}{\thepage}%
585 This chapter is intended to list strategies that may be useful when
586 writing and debugging wxWidgets programs. If you have any good tips,
587 please submit them for inclusion here.
589 \section{Strategies for reducing programming errors
}\label{reducingerrors
}
591 \subsection{Use ASSERT
}\label{useassert
}
593 Although I haven't done this myself within wxWidgets, it is good
594 practice to use ASSERT statements liberally, that check for conditions that
595 should or should not hold, and print out appropriate error messages.
596 These can be compiled out of a non-debugging version of wxWidgets
597 and your application. Using ASSERT is an example of `defensive programming':
598 it can alert you to problems later on.
600 \subsection{Use wxString in preference to character arrays
}\label{usewxstring
}
602 Using wxString can be much safer and more convenient than using char *.
603 Again, I haven't practiced what I'm preaching, but I'm now trying to use
604 wxString wherever possible. You can reduce the possibility of memory
605 leaks substantially, and it is much more convenient to use the overloaded
606 operators than functions such as strcmp. wxString won't add a significant
607 overhead to your program; the overhead is compensated for by easier
608 manipulation (which means less code).
610 The same goes for other data types: use classes wherever possible.
612 \section{Strategies for portability
}\label{portability
}
614 \subsection{Use relative positioning or constraints
}\label{userelativepositioning
}
616 Don't use absolute panel item positioning if you can avoid it. Different GUIs have
617 very differently sized panel items. Consider using the constraint system, although this
618 can be complex to program.
620 Alternatively, you could use alternative .wrc (wxWidgets resource files) on different
621 platforms, with slightly different dimensions in each. Or space your panel items out
624 \subsection{Use wxWidgets resource files
}\label{useresources
}
626 Use .xrc (wxWidgets resource files) where possible, because they can be easily changed
627 independently of source code.
629 \section{Strategies for debugging
}\label{debugstrategies
}
631 \subsection{Positive thinking
}\label{positivethinking
}
633 It is common to blow up the problem in one's imagination, so that it seems to threaten
634 weeks, months or even years of work. The problem you face may seem insurmountable:
635 but almost never is. Once you have been programming for some time, you will be able
636 to remember similar incidents that threw you into the depths of despair. But
637 remember, you always solved the problem, somehow!
639 Perseverance is often the key, even though a seemingly trivial problem
640 can take an apparently inordinate amount of time to solve. In the end,
641 you will probably wonder why you worried so much. That's not to say it
642 isn't painful at the time. Try not to worry -- there are many more important
645 \subsection{Simplify the problem
}\label{simplifyproblem
}
647 Reduce the code exhibiting the problem to the smallest program possible
648 that exhibits the problem. If it is not possible to reduce a large and
649 complex program to a very small program, then try to ensure your code
650 doesn't hide the problem (you may have attempted to minimize the problem
651 in some way: but now you want to expose it).
653 With luck, you can add a small amount of code that causes the program
654 to go from functioning to non-functioning state. This should give a clue
655 to the problem. In some cases though, such as memory leaks or wrong
656 deallocation, this can still give totally spurious results!
658 \subsection{Use a debugger
}\label{usedebugger
}
660 This sounds like facetious advice, but it is surprising how often people
661 don't use a debugger. Often it is an overhead to install or learn how to
662 use a debugger, but it really is essential for anything but the most
665 \subsection{Use logging functions
}\label{uselogging
}
667 There is a variety of logging functions that you can use in your program:
668 see
\helpref{Logging functions
}{logfunctions
}.
670 Using tracing statements may be more convenient than using the debugger
671 in some circumstances (such as when your debugger doesn't support a lot
672 of debugging code, or you wish to print a bunch of variables).
674 \subsection{Use the wxWidgets debugging facilities
}\label{usedebuggingfacilities
}
676 You can use wxDebugContext to check for
677 memory leaks and corrupt memory: in fact in debugging mode, wxWidgets will
678 automatically check for memory leaks at the end of the program if wxWidgets is suitably
679 configured. Depending on the operating system and compiler, more or less
680 specific information about the problem will be logged.
682 You should also use
\helpref{debug macros
}{debugmacros
} as part of a `defensive programming' strategy,
683 scattering wxASSERTs liberally to test for problems in your code as early as possible. Forward thinking
684 will save a surprising amount of time in the long run.
686 See the
\helpref{debugging overview
}{debuggingoverview
} for further information.