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Mention wxString caching in UTF-8 ode

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@55344 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Robert Roebling
2008-08-29 12:46:41 +00:00
parent 3f5506cfd3
commit a6919a6aca
2 changed files with 33 additions and 19 deletions
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45
interface/wx/string.h
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@@ -65,28 +65,41 @@ public:
/**
@class wxString
The wxString class has been completely rewritten for wxWidgets 3.0
and this change was actually the main reason for the calling that
version wxWidgets 3.0.
wxString is a class representing a Unicode character string.
wxString uses @c std::string internally to store its content
unless this is not supported by the compiler or disabled
specifically when building wxWidgets. Therefore wxString
inherits many features from @c std::string. Most
implementations of @c std::string are thread-safe and don't
use reference counting. By default, wxString uses @c std::string
internally even if wxUSE_STL is not defined.
specifically when building wxWidgets and it therefore inherits
many features from @c std::string. Most implementations of
@c std::string are thread-safe and don't use reference counting.
By default, wxString uses @c std::string internally even if
wxUSE_STL is not defined.
Since wxWidgets 3.0 wxString internally uses UCS-2 (basically 2-byte per
character wchar_t and nearly the same as UTF-16) under Windows and
UTF-8 under Unix, Linux and OS X to store its content.
wxString now internally uses UTF-16 under Windows and UTF-8 under
Unix, Linux and OS X to store its content. Note that when iterating
over a UTF-16 string under Windows, the user code has to take care
of surrogate pair handling whereas Windows itself has built-in
support pairs in UTF-16, such as for drawing strings on screen.
Much work has been done to make existing code using ANSI string literals
work as before. If you need to have a wxString that uses wchar_t on Unix
and Linux, too, you can specify this on the command line with the
@c configure @c --disable-utf8 switch.
work as before. If you nonetheless need to have a wxString that uses wchar_t
on Unix and Linux, too, you can specify this on the command line with the
@c configure @c --disable-utf8 switch or you can consider using wxUString
or std::wstring instead.
If you need a Unicode string class with O(1) access on all platforms
you should consider using wxUString.
Since iterating over a wxString by index can become inefficient in UTF-8
mode iterators should be used instead of index based access:
Accessing a UTF-8 string by index can be very inefficient because
a single character is represented by a variable number of bytes so that
the entire string has to be parsed in order to find the character.
Since iterating over a string by index is a common programming technique and
was also possible and encouraged by wxString using the access operator[]()
wxString implements caching of the last used index so that iterating over
a string is a linear operation even in UTF-8 mode.
It is nonetheless recommended to use iterators (instead of index bases
access) like this:
@code
wxString s = "hello";