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[wxWidgets.git] / docs / doxygen / mainpages / devtips.h

/////////////////////////////////////////////////////////////////////////////
// Name:        devtips.h
// Purpose:     Cross-platform development page of the Doxygen manual
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////


/*!

 @page page_multiplatform Multi-platform development with wxWidgets

 This chapter describes the practical details of using wxWidgets. Please
 see the file install.txt for up-to-date installation instructions, and
 changes.txt for differences between versions.

 @li @ref page_multiplatform_includefiles
 @li @ref page_multiplatform_libraries
 @li @ref page_multiplatform_configuration
 @li @ref page_multiplatform_makefiles
 @li @ref page_multiplatform_windowsfiles
 @li @ref page_multiplatform_allocatingobjects
 @li @ref page_multiplatform_architecturedependency
 @li @ref page_multiplatform_conditionalcompilation
 @li @ref page_multiplatform_cpp
 @li @ref page_multiplatform_filehandling

 <hr>


 @section page_multiplatform_includefiles Include files

 The main include file is @c "wx/wx.h"; this includes the most commonly
 used modules of wxWidgets.

 To save on compilation time, include only those header files relevant to the
 source file. If you are using precompiled headers, you should include
 the following section before any other includes:

 @verbatim
 // For compilers that support precompilation, includes "wx.h".
 #include <wx/wxprec.h>

 #ifdef __BORLANDC__
 #pragma hdrstop
 #endif

 #ifndef WX_PRECOMP
 // Include your minimal set of headers here, or wx.h
 #include <wx/wx.h>
 #endif

 ... now your other include files ...
 @endverbatim

 The file @c "wx/wxprec.h" includes @c "wx/wx.h". Although this incantation
 may seem quirky, it is in fact the end result of a lot of experimentation,
 and several Windows compilers to use precompilation which is largely automatic for
 compilers with necessary support. Currently it is used for Visual C++ (including
 embedded Visual C++), Borland C++, Open Watcom C++, Digital Mars C++
 and newer versions of GCC.
 Some compilers might need extra work from the application developer to set the
 build environment up as necessary for the support.



 @section page_multiplatform_libraries Libraries

 Most ports of wxWidgets can create either a static library or a shared
 library. wxWidgets can also be built in multilib and monolithic variants.
 See the @ref page_libs for more information on these.



 @section page_multiplatform_configuration Configuration

 When using project files and makefiles directly to build wxWidgets,
 options are configurable in the file
 @c "wx/XXX/setup.h" where XXX is the required platform (such as msw, motif, gtk, mac). Some
 settings are a matter of taste, some help with platform-specific problems, and
 others can be set to minimize the size of the library. Please see the setup.h file
 and @c install.txt files for details on configuration.

 When using the 'configure' script to configure wxWidgets (on Unix and other platforms where
 configure is available), the corresponding setup.h files are generated automatically
 along with suitable makefiles. When using the RPM packages
 for installing wxWidgets on Linux, a correct setup.h is shipped in the package and
 this must not be changed.



 @section page_multiplatform_makefiles Makefiles

 On Microsoft Windows, wxWidgets has a different set of makefiles for each
 compiler, because each compiler's 'make' tool is slightly different.
 Popular Windows compilers that we cater for, and the corresponding makefile
 extensions, include: Microsoft Visual C++ (.vc), Borland C++ (.bcc),
 OpenWatcom C++ (.wat) and MinGW/Cygwin (.gcc). Makefiles are provided
 for the wxWidgets library itself, samples, demos, and utilities.

 On Linux, Mac and OS/2, you use the 'configure' command to
 generate the necessary makefiles. You should also use this method when
 building with MinGW/Cygwin on Windows.

 We also provide project files for some compilers, such as
 Microsoft VC++. However, we recommend using makefiles
 to build the wxWidgets library itself, because makefiles
 can be more powerful and less manual intervention is required.

 On Windows using a compiler other than MinGW/Cygwin, you would
 build the wxWidgets library from the build/msw directory
 which contains the relevant makefiles.

 On Windows using MinGW/Cygwin, and on Unix, MacOS X and OS/2, you invoke
 'configure' (found in the top-level of the wxWidgets source hierarchy),
 from within a suitable empty directory for containing makefiles, object files and
 libraries.

 For details on using makefiles, configure, and project files,
 please see docs/xxx/install.txt in your distribution, where
 xxx is the platform of interest, such as msw, gtk, x11, mac.



 @section page_multiplatform_windowsfiles Windows-specific files

 wxWidgets application compilation under MS Windows requires at least one
 extra file: a resource file.

 @subsection page_multiplatform_windowsfiles_resources Resource file

 The least that must be defined in the Windows resource file (extension RC)
 is the following statement:

 @verbatim
 #include "wx/msw/wx.rc"
 @endverbatim

 which includes essential internal wxWidgets definitions.  The resource script
 may also contain references to icons, cursors, etc., for example:

 @verbatim
 wxicon icon wx.ico
 @endverbatim

 The icon can then be referenced by name when creating a frame icon. See
 the MS Windows SDK documentation.

 @note include wx.rc @e after any ICON statements
       so programs that search your executable for icons (such
       as the Program Manager) find your application icon first.



 @section page_multiplatform_allocatingobjects Allocating and deleting wxWidgets objects

 In general, classes derived from wxWindow must dynamically allocated
 with @e new and deleted with @e delete. If you delete a window,
 all of its children and descendants will be automatically deleted,
 so you don't need to delete these descendants explicitly.

 When deleting a frame or dialog, use @b Destroy rather than @b delete so
 that the wxWidgets delayed deletion can take effect. This waits until idle time
 (when all messages have been processed) to actually delete the window, to avoid
 problems associated with the GUI sending events to deleted windows.

 Don't create a window on the stack, because this will interfere
 with delayed deletion.

 If you decide to allocate a C++ array of objects (such as wxBitmap) that may
 be cleaned up by wxWidgets, make sure you delete the array explicitly
 before wxWidgets has a chance to do so on exit, since calling @e delete on
 array members will cause memory problems.

 wxColour can be created statically: it is not automatically cleaned
 up and is unlikely to be shared between other objects; it is lightweight
 enough for copies to be made.

 Beware of deleting objects such as a wxPen or wxBitmap if they are still in use.
 Windows is particularly sensitive to this: so make sure you
 make calls like wxDC::SetPen(wxNullPen) or wxDC::SelectObject(wxNullBitmap) before deleting
 a drawing object that may be in use. Code that doesn't do this will probably work
 fine on some platforms, and then fail under Windows.



 @section page_multiplatform_architecturedependency Architecture dependency

 A problem which sometimes arises from writing multi-platform programs is that
 the basic C types are not defined the same on all platforms. This holds true
 for both the length in bits of the standard types (such as int and long) as
 well as their byte order, which might be little endian (typically
 on Intel computers) or big endian (typically on some Unix workstations). wxWidgets
 defines types and macros that make it easy to write architecture independent
 code. The types are:

 wxInt32, wxInt16, wxInt8, wxUint32, wxUint16 = wxWord, wxUint8 = wxByte

 where wxInt32 stands for a 32-bit signed integer type etc. You can also check
 which architecture the program is compiled on using the wxBYTE_ORDER define
 which is either wxBIG_ENDIAN or wxLITTLE_ENDIAN (in the future maybe wxPDP_ENDIAN
 as well).

 The macros handling bit-swapping with respect to the applications endianness
 are described in the @ref page_macro_cat_byteorder section.



 @section page_multiplatform_conditionalcompilation Conditional compilation

 One of the purposes of wxWidgets is to reduce the need for conditional
 compilation in source code, which can be messy and confusing to follow.
 However, sometimes it is necessary to incorporate platform-specific
 features (such as metafile use under MS Windows). The @ref page_wxusedef
 symbols listed in the file @c setup.h may be used for this purpose,
 along with any user-supplied ones.



 @section page_multiplatform_cpp C++ issues

 The following documents some miscellaneous C++ issues.

 @subsection page_multiplatform_cpp_templates Templates

 wxWidgets does not use templates (except for some advanced features that
 are switched off by default) since it is a notoriously unportable feature.

 @subsection page_multiplatform_cpp_rtti RTTI

 wxWidgets does not use C++ run-time type information since wxWidgets provides
 its own run-time type information system, implemented using macros.

 @subsection page_multiplatform_cpp_null Type of NULL

 Some compilers (e.g. the native IRIX cc) define NULL to be 0L so that
 no conversion to pointers is allowed. Because of that, all these
 occurrences of NULL in the GTK+ port use an explicit conversion such
 as

 @code
   wxWindow *my_window = (wxWindow*) NULL;
 @endcode

 It is recommended to adhere to this in all code using wxWidgets as
 this make the code (a bit) more portable.

 @subsection page_multiplatform_cpp_precompiledheaders Precompiled headers

 Some compilers, such as Borland C++ and Microsoft C++, support
 precompiled headers. This can save a great deal of compiling time. The
 recommended approach is to precompile @c "wx.h", using this
 precompiled header for compiling both wxWidgets itself and any
 wxWidgets applications. For Windows compilers, two dummy source files
 are provided (one for normal applications and one for creating DLLs)
 to allow initial creation of the precompiled header.

 However, there are several downsides to using precompiled headers. One
 is that to take advantage of the facility, you often need to include
 more header files than would normally be the case. This means that
 changing a header file will cause more recompilations (in the case of
 wxWidgets, everything needs to be recompiled since everything includes @c "wx.h" !)

 A related problem is that for compilers that don't have precompiled
 headers, including a lot of header files slows down compilation
 considerably. For this reason, you will find (in the common
 X and Windows parts of the library) conditional
 compilation that under Unix, includes a minimal set of headers;
 and when using Visual C++, includes @c wx.h. This should help provide
 the optimal compilation for each compiler, although it is
 biased towards the precompiled headers facility available
 in Microsoft C++.



 @section page_multiplatform_filehandling File handling

 When building an application which may be used under different
 environments, one difficulty is coping with documents which may be
 moved to different directories on other machines. Saving a file which
 has pointers to full pathnames is going to be inherently unportable.

 One approach is to store filenames on their own, with no directory
 information. The application then searches into a list of standard
 paths (platform-specific) through the use of wxStandardPaths.

 Eventually you may want to use also the wxPathList class.

 Nowadays the limitations of DOS 8+3 filenames doesn't apply anymore.
 Most modern operating systems allow at least 255 characters in the filename;
 the exact maximum length, as well as the characters allowed in the filenames,
 are OS-specific so you should try to avoid extremely long (> 255 chars) filenames
 and/or filenames with non-ANSI characters.

 Another thing you need to keep in mind is that all Windows operating systems
 are case-insensitive, while Unix operating systems (Linux, Mac, etc) are
 case-sensitive.

 Also, for text files, different OSes use different End Of Lines (EOL).
 Windows uses CR+LF convention, Linux uses LF only, Mac CR only.

 The wxTextFile, wxTextInputStream, wxTextOutputStream classes help to abstract
 from these differences.
 Of course, there are also 3rd party utilities such as @c dos2unix and @c unix2dos
 which do the EOL conversions.

 See also the @ref page_func_cat_file section of the reference
 manual for the description of miscellaneous file handling functions.

*/