This topic describes backwards-incompatible changes in wxWidgets 3.0 compared to the last stable release and is very important to read if you are updating from the 2.8 or an older version.
And even if you hadn't used any previous version of wxWidgets and are starting directly with 3.0, it can still be useful to have at least a quick look at it just to know that some of the older examples and tutorials may not be applicable any more to wxWidgets 3.0.
The incompatible changes can be grouped into the following categories:
If you used Unicode build of wxWidgets 2.8 or previous version, please read Unicode Support in wxWidgets for the details about how the API changed in 3.0 as a lot of the information which was correct before doesn't apply any longer.
For example, the notorious (due to the confusion they created) macros
_T() are not needed at all any longer. Basically, you can remove them from any code which used them. On the other hand, there is no particular harm in leaving them neither as the code will still compile and work correctly – you only need to remove them if you think that your code looks tidier without them. You also don't need to use
wxChar any longer but can directly use the standard
wchar_t type even if, again,
wxChar continues to work.
The most serious backwards-incompatible change is related to the change of return type of wxString::c_str() method: it returns a special proxy object instead of a simple
wchar_t* now. Because of this, you cannot pass its result to any standard vararg functions such as
printf() any more as described in Unicode-Related Compilation Errors. All wxWidgets functions, such as wxPrintf(), wxLogMessage() &c still work with it, but passing it to
printf() will now result in a crash. It is strongly advised to recompile your code with a compiler warning about passing non-POD objects to vararg functions, such as g++.
The change of the type of wxString::c_str() can also result in compilation errors when passing its result to a function overloaded to take both narrow and wide strings and in this case you must select the version which you really want to use, e.g.:
A common example of such problem arises with
std::fstream class constructor in Microsoft Visual C++ standard library implementation. In addition to a constructor from
char * which this class must have, it also provides a constructor taking a wide character file name. Because of this, code like the following
does not compile when using Microsoft Visual C++ and needs to be changed to use mb_str() (which will not work for file names containing Unicode characters, consider using wxWidgets classes and functions to work with such file names as they are not supported by standard C++ library).
The other class of incompatible changes is due to modifying some virtual methods to use
wxString parameters instead of
wxChar* ones to make them accept both narrow and wide strings. This is not a problem if you simply call these functions but you need to change the signature of the derived class versions if you override them as otherwise they wouldn't be called any more. Again, the best way to ensure that this problem doesn't arise is to rebuild your code using a compiler which warns about function signature mismatch (you can use
-Woverloaded-virtual g++ option).
Finally, a few structure fields, notable
description fields have been changed to be of type
char* instead of
wxChar* so you will need to remove
_T() if you used it with their initializers.
The simplest solution is to cast the enum value to int, e.g.
Of course, this will change the format of the wxConfig output which may be undesirable.