docs/doxygen/devtips.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        devtips.h
   3 // Purpose:     Cross-platform development page of the Doxygen manual
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9
  10 /*!
  11
  12  @page multiplatform_page Multi-platform development with wxWidgets
  13
  14  This chapter describes the practical details of using wxWidgets. Please
  15  see the file install.txt for up-to-date installation instructions, and
  16  changes.txt for differences between versions.
  17
  18  @li @ref includefiles
  19  @li @ref libraries
  20  @li @ref configuration
  21  @li @ref makefiles
  22  @li @ref windowsfiles
  23  @li @ref allocatingobjects
  24  @li @ref architecturedependency
  25  @li @ref conditionalcompilation
  26  @li @ref cpp
  27  @li @ref filehandling
  28
  29  <hr>
  30
  31
  32  @section includefiles Include files
  33
  34  The main include file is @c "wx/wx.h"; this includes the most commonly
  35  used modules of wxWidgets.
  36
  37  To save on compilation time, include only those header files relevant to the
  38  source file. If you are using precompiled headers, you should include
  39  the following section before any other includes:
  40
  41  @verbatim
  42  // For compilers that support precompilation, includes "wx.h".
  43  #include <wx/wxprec.h>
  44
  45  #ifdef __BORLANDC__
  46  #pragma hdrstop
  47  #endif
  48
  49  #ifndef WX_PRECOMP
  50  // Include your minimal set of headers here, or wx.h
  51  #include <wx/wx.h>
  52  #endif
  53
  54  ... now your other include files ...
  55  @endverbatim
  56
  57  The file @c "wx/wxprec.h" includes @c "wx/wx.h". Although this incantation
  58  may seem quirky, it is in fact the end result of a lot of experimentation,
  59  and several Windows compilers to use precompilation which is largely automatic for
  60  compilers with necessary support. Currently it is used for Visual C++ (including
  61  embedded Visual C++), Borland C++, Open Watcom C++, Digital Mars C++
  62  and newer versions of GCC.
  63  Some compilers might need extra work from the application developer to set the
  64  build environment up as necessary for the support.
  65
  66
  67
  68  @section libraries Libraries
  69
  70  Most ports of wxWidgets can create either a static library or a shared
  71  library. wxWidgets can also be built in multilib and monolithic variants.
  72  See the @ref libraries_page for more information on these.
  73
  74
  75
  76  @section configuration Configuration
  77
  78  When using project files and makefiles directly to build wxWidgets,
  79  options are configurable in the file
  80  @c "wx/XXX/setup.h" where XXX is the required platform (such as msw, motif, gtk, mac). Some
  81  settings are a matter of taste, some help with platform-specific problems, and
  82  others can be set to minimize the size of the library. Please see the setup.h file
  83  and @c install.txt files for details on configuration.
  84
  85  When using the 'configure' script to configure wxWidgets (on Unix and other platforms where
  86  configure is available), the corresponding setup.h files are generated automatically
  87  along with suitable makefiles. When using the RPM packages
  88  for installing wxWidgets on Linux, a correct setup.h is shipped in the package and
  89  this must not be changed.
  90
  91
  92
  93  @section makefiles Makefiles
  94
  95  On Microsoft Windows, wxWidgets has a different set of makefiles for each
  96  compiler, because each compiler's 'make' tool is slightly different.
  97  Popular Windows compilers that we cater for, and the corresponding makefile
  98  extensions, include: Microsoft Visual C++ (.vc), Borland C++ (.bcc),
  99  OpenWatcom C++ (.wat) and MinGW/Cygwin (.gcc). Makefiles are provided
 100  for the wxWidgets library itself, samples, demos, and utilities.
 101
 102  On Linux, Mac and OS/2, you use the 'configure' command to
 103  generate the necessary makefiles. You should also use this method when
 104  building with MinGW/Cygwin on Windows.
 105
 106  We also provide project files for some compilers, such as
 107  Microsoft VC++. However, we recommend using makefiles
 108  to build the wxWidgets library itself, because makefiles
 109  can be more powerful and less manual intervention is required.
 110
 111  On Windows using a compiler other than MinGW/Cygwin, you would
 112  build the wxWidgets library from the build/msw directory
 113  which contains the relevant makefiles.
 114
 115  On Windows using MinGW/Cygwin, and on Unix, MacOS X and OS/2, you invoke
 116  'configure' (found in the top-level of the wxWidgets source hierarchy),
 117  from within a suitable empty directory for containing makefiles, object files and
 118  libraries.
 119
 120  For details on using makefiles, configure, and project files,
 121  please see docs/xxx/install.txt in your distribution, where
 122  xxx is the platform of interest, such as msw, gtk, x11, mac.
 123
 124
 125
 126  @section windowsfiles Windows-specific files
 127
 128  wxWidgets application compilation under MS Windows requires at least one
 129  extra file: a resource file.
 130
 131  @subsection resources Resource file
 132
 133  The least that must be defined in the Windows resource file (extension RC)
 134  is the following statement:
 135
 136  @verbatim
 137  #include "wx/msw/wx.rc"
 138  @endverbatim
 139
 140  which includes essential internal wxWidgets definitions.  The resource script
 141  may also contain references to icons, cursors, etc., for example:
 142
 143  @verbatim
 144  wxicon icon wx.ico
 145  @endverbatim
 146
 147  The icon can then be referenced by name when creating a frame icon. See
 148  the MS Windows SDK documentation.
 149
 150  @note include wx.rc @e after any ICON statements
 151        so programs that search your executable for icons (such
 152        as the Program Manager) find your application icon first.
 153
 154
 155
 156  @section allocatingobjects Allocating and deleting wxWidgets objects
 157
 158  In general, classes derived from wxWindow must dynamically allocated
 159  with @e new and deleted with @e delete. If you delete a window,
 160  all of its children and descendants will be automatically deleted,
 161  so you don't need to delete these descendants explicitly.
 162
 163  When deleting a frame or dialog, use @b Destroy rather than @b delete so
 164  that the wxWidgets delayed deletion can take effect. This waits until idle time
 165  (when all messages have been processed) to actually delete the window, to avoid
 166  problems associated with the GUI sending events to deleted windows.
 167
 168  Don't create a window on the stack, because this will interfere
 169  with delayed deletion.
 170
 171  If you decide to allocate a C++ array of objects (such as wxBitmap) that may
 172  be cleaned up by wxWidgets, make sure you delete the array explicitly
 173  before wxWidgets has a chance to do so on exit, since calling @e delete on
 174  array members will cause memory problems.
 175
 176  wxColour can be created statically: it is not automatically cleaned
 177  up and is unlikely to be shared between other objects; it is lightweight
 178  enough for copies to be made.
 179
 180  Beware of deleting objects such as a wxPen or wxBitmap if they are still in use.
 181  Windows is particularly sensitive to this: so make sure you
 182  make calls like wxDC::SetPen(wxNullPen) or wxDC::SelectObject(wxNullBitmap) before deleting
 183  a drawing object that may be in use. Code that doesn't do this will probably work
 184  fine on some platforms, and then fail under Windows.
 185
 186
 187
 188  @section architecturedependency Architecture dependency
 189
 190  A problem which sometimes arises from writing multi-platform programs is that
 191  the basic C types are not defined the same on all platforms. This holds true
 192  for both the length in bits of the standard types (such as int and long) as
 193  well as their byte order, which might be little endian (typically
 194  on Intel computers) or big endian (typically on some Unix workstations). wxWidgets
 195  defines types and macros that make it easy to write architecture independent
 196  code. The types are:
 197
 198  wxInt32, wxInt16, wxInt8, wxUint32, wxUint16 = wxWord, wxUint8 = wxByte
 199
 200  where wxInt32 stands for a 32-bit signed integer type etc. You can also check
 201  which architecture the program is compiled on using the wxBYTE_ORDER define
 202  which is either wxBIG_ENDIAN or wxLITTLE_ENDIAN (in the future maybe wxPDP_ENDIAN
 203  as well).
 204
 205  The macros handling bit-swapping with respect to the applications endianness
 206  are described in the @ref byteordermacros section.
 207
 208
 209
 210  @section conditionalcompilation Conditional compilation
 211
 212  One of the purposes of wxWidgets is to reduce the need for conditional
 213  compilation in source code, which can be messy and confusing to follow.
 214  However, sometimes it is necessary to incorporate platform-specific
 215  features (such as metafile use under MS Windows). The @ref wxusedef
 216  symbols listed in the file @c setup.h may be used for this purpose,
 217  along with any user-supplied ones.
 218
 219
 220
 221  @section cpp C++ issues
 222
 223  The following documents some miscellaneous C++ issues.
 224
 225  @subsection templates Templates
 226
 227  wxWidgets does not use templates (except for some advanced features that
 228  are switched off by default) since it is a notoriously unportable feature.
 229
 230  @subsection rtti RTTI
 231
 232  wxWidgets does not use C++ run-time type information since wxWidgets provides
 233  its own run-time type information system, implemented using macros.
 234
 235  @subsection null Type of NULL
 236
 237  Some compilers (e.g. the native IRIX cc) define NULL to be 0L so that
 238  no conversion to pointers is allowed. Because of that, all these
 239  occurrences of NULL in the GTK+ port use an explicit conversion such
 240  as
 241
 242  @code
 243    wxWindow *my_window = (wxWindow*) NULL;
 244  @endcode
 245
 246  It is recommended to adhere to this in all code using wxWidgets as
 247  this make the code (a bit) more portable.
 248
 249  @subsection precompiledheaders Precompiled headers
 250
 251  Some compilers, such as Borland C++ and Microsoft C++, support
 252  precompiled headers. This can save a great deal of compiling time. The
 253  recommended approach is to precompile @c "wx.h", using this
 254  precompiled header for compiling both wxWidgets itself and any
 255  wxWidgets applications. For Windows compilers, two dummy source files
 256  are provided (one for normal applications and one for creating DLLs)
 257  to allow initial creation of the precompiled header.
 258
 259  However, there are several downsides to using precompiled headers. One
 260  is that to take advantage of the facility, you often need to include
 261  more header files than would normally be the case. This means that
 262  changing a header file will cause more recompilations (in the case of
 263  wxWidgets, everything needs to be recompiled since everything includes @c "wx.h" !)
 264
 265  A related problem is that for compilers that don't have precompiled
 266  headers, including a lot of header files slows down compilation
 267  considerably. For this reason, you will find (in the common
 268  X and Windows parts of the library) conditional
 269  compilation that under Unix, includes a minimal set of headers;
 270  and when using Visual C++, includes @c wx.h. This should help provide
 271  the optimal compilation for each compiler, although it is
 272  biased towards the precompiled headers facility available
 273  in Microsoft C++.
 274
 275
 276
 277  @section filehandling File handling
 278
 279  When building an application which may be used under different
 280  environments, one difficulty is coping with documents which may be
 281  moved to different directories on other machines. Saving a file which
 282  has pointers to full pathnames is going to be inherently unportable.
 283
 284  One approach is to store filenames on their own, with no directory
 285  information. The application then searches into a list of standard
 286  paths (platform-specific) through the use of wxStandardPaths.
 287
 288  Eventually you may want to use also the wxPathList class.
 289
 290  Nowadays the limitations of DOS 8+3 filenames doesn't apply anymore.
 291  Most modern operating systems allow at least 255 characters in the filename;
 292  the exact maximum length, as well as the characters allowed in the filenames,
 293  are OS-specific so you should try to avoid extremely long (> 255 chars) filenames
 294  and/or filenames with non-ANSI characters.
 295
 296  Another thing you need to keep in mind is that all Windows operating systems
 297  are case-insensitive, while Unix operating systems (Linux, Mac, etc) are
 298  case-sensitive.
 299
 300  Also, for text files, different OSes use different End Of Lines (EOL).
 301  Windows uses CR+LF convention, Linux uses LF only, Mac CR only.
 302
 303  The wxTextFile, wxTextInputStream, wxTextOutputStream classes help to abstract
 304  from these differences.
 305  Of course, there are also 3rd party utilities such as @c dos2unix and @c unix2dos
 306  which do the EOL conversions.
 307
 308  See also the @ref filefunctions section of the reference
 309  manual for the description of miscellaneous file handling functions.
 310
 311 */