wxWidgets FAQ: Questions common to all platforms
See also top-level FAQ page.
List of questions in this category
All windows and controls in wxWidgets programs are created using new
but you shouldn't use delete to free them. This doesn't result
in memory leaks because wxWidgets takes care of this: all objects derived from
wxWindow will be deleted automatically by the library when the corresponding
real, on screen, window is destroyed. Thus, the top level window objects are
deleted when you call Close() or Destroy() and all the child
windows are deleted just before the parent window is. More details about the
top level windows can be found in the ``Window deletion overview'' in
wxWidgets also automatically deletes some other kind of the objects, notably
the sizer or constraint associated with the window -- this happens just before
the window itself is deleted. The sizers, in turn, delete their child sizers
automatically as well so in a typical situation you don't have to worry
about freeing the sizers you create. Note, however, that if you
Remove() a sizer from the window, it isn't automatically deleted
any more and you are responsable for doing this.
Please look at the event wxWidgets sample source code, it shows how to
do this among other things. Note that the way custom events are defined has
changed in wxWidgets 2.3.1 as compared to the previous releases.
Unfortunately in the current wxWidgets version (2.4.0 as of this writing) this
is not possible: the TAB order of the control (that is, the order in which the
controls gain focus when the user repeatedly presses the <TAB>
key) is fixed and is the same as the order of the controls creation.
Changing this should become possible in future versions of wxWidgets as soon as
we come up with a nice API for this feature.
First of all, _T() is exactly the same as wxT() (it exists
only because it should be more familiar to Windows programmers) which reduces
the problem of choosing among the macros to use somewhat.
Here is some pseudo-code for choosing the macro to use between the remaining
possibilities, that is whether to use wxT(), use _() or not
use any of them:
if ( string should be translated )
else if ( string should be in Unicode in Unicode build )
just use "string" normally
Note that if you don't care about Unicode at all, you don't have to use
wxT() at all. On the contrary, if you do, note that _()
takes care of it internally so if you use it your code will compile in both
the ANSI and Unicode builds.
Please see the description of these macros in the manual for more details.
Pressing Esc will close the dialog if and only if it has a button
with wxID_CANCEL id.
These message boxes are probably due to calls to wxLogError() or
other log functions from wxWidgets code. To completely suppress them you
may use wxLogNull class, please see the manual for details. Do note, however,
that a better solution is to avoid the error in the first place as suppressing
these error message might hide other, important, ones.
This topic is covered in the technical note Writing installers.
The following code:
str.Printf(wxT("My string is %s"), wxString("whatever"));
does not work. Unfortunately, it may seem to work fine under
Windows because of a compiler quirk there but passing a wxString object to a
function taking a variable number of arguments such as Printf() is
undefined behaviour in C++. Accordingly, it will simply crash under most
platforms but may even "work" on some of them.
You must use c_str() to make the above code work, i.e. write this
str.Printf(wxT("My string is %s"), wxString("whatever").c_str());
Note that g++ should give you an error when passing an object to a vararg
function like this -- another reason to compile your code with g++ even if you
normally use another compiler.
If you use the wxXRC_USE_LOCALE flag (which is on by default), strings
from XRC files are translated using wxLocale. wxLocale assumes the strings
are in ASCII - if the are not, wxXmlResource leaves them in UTF-8 encoding in
ANSI build of wxWidgets. Either don't use wxXRC_USE_LOCALE or use
translate="0" attribute in XRC files. More details can be found