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 wxT()
and _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 either 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 char*
or 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 const
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 const
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 wxCmdLineEntryDesc::shortName
, longName
and description
fields have been changed to be of type const
char*
instead of const
wxChar*
so you will need to remove wxT()
or _T()
if you used it with their initializers.
Calling wxConfig::Write() with an enum value will fail to compile because wxConfig now tries to convert all unknown types to wxString automatically using wxToString() function.
The simplest solution is to cast the enum value to int, e.g.
Another possibility which exists now is to provide an overload of wxToString() (and wxFromString()) for your own type, e.g.
Of course, this will change the format of the wxConfig output which may be undesirable.