@page overview_treectrl wxTreeCtrl overview
Classes: #wxTreeCtrl, #wxImageList
+
The tree control displays its items in a tree like structure. Each item has its
own (optional) icon and a label. An item may be either collapsed (meaning that
its children are not visible) or expanded (meaning that its children are
shown). Each item in the tree is identified by its @e itemId which is of
opaque data type @e wxTreeItemId. You can test whether an item is valid
by calling wxTreeItemId::IsOk.
+
The items text and image may be retrieved and changed with
#GetItemText/#SetItemText
and
and another one for selected state which is set/retrieved with
#SetItemSelectedImage/#GetItemSelectedImage
functions, but this functionality might be unavailable on some platforms.
+
Tree items have several attributes: an item may be selected or not, visible or
not, bold or not. It may also be expanded or collapsed. All these attributes
may be retrieved with the corresponding functions:
selected, selecting another one (with
#SelectItem) automatically unselects the
previously selected one.
+
In addition to its icon and label, a user-specific data structure may be associated
with all tree items. If you wish to do it, you should derive a class from @e wxTreeItemData which is a very simple class having only one function @e GetId() which returns the id of the item this data is associated with. This
data will be freed by the control itself when the associated item is deleted
#SetItemData(@NULL) to prevent the tree from
deleting the pointer second time). The associated data may be retrieved with
#GetItemData() function.
+
Working with trees is relatively straightforward if all the items are added to
the tree at the moment of its creation. However, for large trees it may be
very inefficient. To improve the performance you may want to delay adding the
under the item being expanded should be added, but, of course, only when this
event is received for the first time for this item - otherwise, the items would
be added twice if the user expands/collapses/re-expands the branch.
+
The tree control provides functions for enumerating its items. There are 3
groups of enumeration functions: for the children of a given item, for the
sibling of the given item and for the visible items (those which are currently
#GetFirstChild and to
#GetNextChild should be the same variable (and
that nothing should be done with it by the user code).
+
Among other features of the tree control are: item sorting with
#SortChildren which uses the user-defined comparison
function #OnCompareItems (by default the
for implementing drag-and-drop in the tree) with
#HitTest and editing of the tree item labels in
place (see #EditLabel).
+
Finally, the tree control has a keyboard interface: the cursor navigation (arrow) keys
may be used to change the current selection. HOME and END are used to go to
the first/last sibling of the current item. '+', '-' and '*' expand, collapse
This section briefly describes the state of the Unicode support in wxWidgets.
Read it if you want to know more about how to write programs able to work with
characters from languages other than English.
- @ref whatisunicode_overview
- @ref unicodeandansi_overview
- @ref unicodeinsidewxw_overview
- @ref unicodeoutsidewxw_overview
- @ref unicodesettings_overview
- @ref topic8_overview
+ @li @ref overview_whatisunicode
+ @li @ref overview_unicodeandansi
+ @li @ref overview_unicodeinsidewxw
+ @li @ref overview_unicodeoutsidewxw
+ @li @ref overview_unicodesettings
+ @li @ref overview_topic8
- @section whatisunicode What is Unicode?
+
+ @section overview_whatisunicode What is Unicode?
wxWidgets has support for compiling in Unicode mode
on the platforms which support it. Unicode is a standard for character
multilingual plane) and possible 2^32 of them instead of the usual 256 and
is sufficient to encode all of the world languages at once. More details about
Unicode may be found at #http://www.unicode.org.
+
As this solution is obviously preferable to the previous ones (think of
incompatible encodings for the same language, locale chaos and so on), many
modern operating systems support it. The probably first example is Windows NT
which uses only Unicode internally since its very first version.
+
Writing internationalized programs is much easier with Unicode and, as the
support for it improves, it should become more and more so. Moreover, in the
Windows NT/2000 case, even the program which uses only standard ASCII can profit
need for the system to convert all strings the program uses to/from Unicode
each time a system call is made.
- @section unicodeandansi Unicode and ANSI modes
+ @section overview_unicodeandansi Unicode and ANSI modes
As not all platforms supported by wxWidgets support Unicode (fully) yet, in
many cases it is unwise to write a program which can only work in Unicode
environment. A better solution is to write programs in such way that they may
be compiled either in ANSI (traditional) mode or in the Unicode one.
+
This can be achieved quite simply by using the means provided by wxWidgets.
Basically, there are only a few things to watch out for:
- Character type (@c char or @c wchar_t)
- Literal strings (i.e. @c "Hello, world!" or @c '*')
- String functions (@c strlen(), @c strcpy(), ...)
- Special preprocessor tokens (@c __FILE__, @c __DATE__
+ - Character type (@c char or @c wchar_t)
+ - Literal strings (i.e. @c "Hello, world!" or @c '*')
+ - String functions (@c strlen(), @c strcpy(), ...)
+ - Special preprocessor tokens (@c __FILE__, @c __DATE__
and @c __TIME__)
program takes 2 bytes instead of usual one, so another type should be used to
store the characters (@c char only holds 1 byte usually). This type is
called @c wchar_t which stands for @e wide-character type.
+
Also, the string and character constants should be encoded using wide
characters (@c wchar_t type) which typically take 2 or 4 bytes instead
of @c char which only takes one. This is achieved by using the standard C
becomes a @e long constant, i.e. a wide character one. To make things a bit
more readable, you are also allowed to prefix the constant with @c 'L'
instead of putting it after it.
+
Of course, the usual standard C functions don't work with @c wchar_t
strings, so another set of functions exists which do the same thing but accept
@c wchar_t * instead of @c char *. For example, a function to get the
@c strlen() - you see that the only difference is that the "str" prefix
standing for "string" has been replaced with "wcs" standing for "wide-character
string").
+
And finally, the standard preprocessor tokens enumerated above expand to ANSI
strings but it is more likely that Unicode strings are wanted in the Unicode
build. wxWidgets provides the macros @c __TFILE__, @c __TDATE__
and @c __TTIME__ which behave exactly as the standard ones except that
they produce ANSI strings in ANSI build and Unicode ones in the Unicode build.
+
To summarize, here is a brief example of how a program which can be compiled
in both ANSI and Unicode modes could look like:
program would have had!). Luckily, there is another way - see the next
section.
- @section unicodeinsidewxw Unicode support in wxWidgets
+ @section overview_unicodeinsidewxw Unicode support in wxWidgets
In wxWidgets, the code fragment from above should be written instead:
at all. Instead, we define some types and macros which behave differently in
the Unicode and ANSI builds and allow us to avoid using conditional
compilation in the program itself.
+
We have a @c wxChar type which maps either on @c char or @c wchar_t
depending on the mode in which program is being compiled. There is no need for
a separate type for strings though, because the standard
#wxString supports Unicode, i.e. it stores either ANSI or
Unicode strings depending on the compile mode.
+
Finally, there is a special #wxT() macro which should enclose all
literal strings in the program. As it is easy to see comparing the last
fragment with the one above, this macro expands to nothing in the (usual) ANSI
mode and prefixes @c 'L' to its argument in the Unicode mode.
+
The important conclusion is that if you use @c wxChar instead of
@c char, avoid using C style strings and use @c wxString instead and
don't forget to enclose all string literals inside #wxT() macro, your
program automatically becomes (almost) Unicode compliant!
- Just let us state once again the rules:
+ Just let us state once again the rules:
- Always use @c wxChar instead of @c char
- Always enclose literal string constants in #wxT() macro
+ - Always use @c wxChar instead of @c char
+ - Always enclose literal string constants in #wxT() macro
unless they're already converted to the right representation (another standard
wxWidgets macro #_() does it, for example, so there is no
need for @c wxT() in this case) or you intend to pass the constant directly
to an external function which doesn't accept wide-character strings.
- Use @c wxString instead of C style strings.
-
+ - Use @c wxString instead of C style strings.
-
- @section unicodeoutsidewxw Unicode and the outside world
+ @section overview_unicodeoutsidewxw Unicode and the outside world
We have seen that it was easy to write Unicode programs using wxWidgets types
and macros, but it has been also mentioned that it isn't quite enough.
ANSI strings (a notable exception is the entire Win32 API which accepts either
Unicode or ANSI strings and which thus makes it unnecessary to ever perform
any conversions in the program). GTK 2.0 only accepts UTF-8 strings.
+
To get an ANSI string from a wxString, you may use the
mb_str() function which always returns an ANSI
string (independently of the mode - while the usual
representation which is either ASCII or Unicode). More rarely used, but still
useful, is wc_str() function which always returns
the Unicode string.
+
Sometimes it is also necessary to go from ANSI strings to wxStrings.
In this case, you can use the converter-constructor, as follows:
This code also compiles fine under a non-Unicode build of wxWidgets,
but in that case the converter is ignored.
+
For more information about converters and Unicode see
- the @ref mbconvclasses_overview.
+ the @ref overview_mbconvclasses.
- @section unicodesettings Unicode-related compilation settings
+ @section overview_unicodesettings Unicode-related compilation settings
You should define @c wxUSE_UNICODE to 1 to compile your program in
Unicode mode. This currently works for wxMSW, wxGTK, wxMac and wxX11. If you
compile your program in ANSI mode you can still define @c wxUSE_WCHAR_T
to get some limited support for @c wchar_t type.
+
This will allow your program to perform conversions between Unicode strings and
- ANSI ones (using @ref mbconvclasses_overview)
+ ANSI ones (using @ref overview_mbconvclasses)
and construct wxString objects from Unicode strings (presumably read
from some external file or elsewhere).
- @section topic8 Traps for the unwary
-
-
+ @section overview_topic8 Traps for the unwary
- Casting c_str() to void* is now char*, not wxChar*
- Passing c_str(), mb_str() or wc_str() to variadic functions
+ - Casting c_str() to void* is now char*, not wxChar*
+ - Passing c_str(), mb_str() or wc_str() to variadic functions
doesn't work
*/
projects / wxWidgets.git / commitdiff
