See also top-level FAQ page.
List of questions in this category
- Who deletes all the windows I create?
- How to create and use custom events?
- Why doesn't my code work when I create a window from a thread?
- How can I set the TAB order of the controls?
- What is the difference between
- Why doesn't
Escclose my dialog?
- How can I get rid of message boxes with error messages?
- How can I retrieve the path containing my executable?
- Printf(str) works perfectly under Windows but crashes under Unix, why?
- How do I write a Unix makefile for my program?
- XRC can't display non-ASCII characters correctly
Who deletes all the windows I create?
All windows and controls in wxWidgets programs are created using
new but you
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
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 the manual.
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.
How to create and use custom events?
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.
Why doesn't my code work when I create a window from a thread?
Using any GUI functions from the thread other than the main one (the one running the application event loop) is not supported, in particular creating windows from a worker thread will never work. If you need to do anything from the worker thread the simplest way to do it is to post a custom event to the main thread asking it to do whatever is necessary.
How can I set the TAB order of the controls?
Starting from wxWidgets 2.8 you can call wxWindow::MoveBeforeInTabOrder() and MoveAfterInTabOrder() to change the position of a child window in the TAB chain. Notice that by default the TAB order is the same as the order of creation.
What is the difference between
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
_() or not use any of
if ( string should be translated ) use _("string") else if ( string should be in Unicode in Unicode build ) use wxT("string") else just use "string" normally
Note that if you don't care about Unicode at all, you don't have to use
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.
Esc close my dialog?
Esc will close the dialog if and only if it has a button with
How can I get rid of message boxes with error messages?
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.
How can I retrieve the path containing my executable?
This topic is covered in the installers tutorial.
Printf(str) works perfectly under Windows but crashes under Unix, why?
The following code:
wxString str; 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 instead:
wxString str; 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.
How do I write a Unix makefile for my program?
The simplest way to write a makefile is to copy
from the wxWidgets distribution and adapt it to your needs. Notice that you
should not use the
Makefile file from the same directory as it only works
for the samples because it assumes that the program being built is inside
wxWidgets source tree.
makefile.unx files use
wx-config instead and are more flexible. The
minimal makefile has comments inside it explaining how to adapt it for your
XRC can't display non-ASCII characters correctly
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 builds of
wxWidgets. Either don't use
wxXRC_USE_LOCALE or use
in XRC files.