Doxygen topic overview cleanups.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52088 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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Bryan Petty
2008-02-25 10:50:43 +00:00
parent ed8c374dd7
commit 728449503c
4 changed files with 825 additions and 1365 deletions

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@@ -37,7 +37,7 @@
@li @subpage overview_backwardcompat @li @subpage overview_backwardcompat
@li @subpage overview_runtimeclass @li @subpage overview_runtimeclass
@li @subpage overview_trefcount @li @subpage overview_refcount
@li @subpage overview_app @li @subpage overview_app
@li @subpage overview_unicode @li @subpage overview_unicode
@li @subpage overview_mbconvclasses @li @subpage overview_mbconvclasses
@@ -63,7 +63,7 @@
@li @subpage overview_thread @li @subpage overview_thread
@li @subpage overview_config @li @subpage overview_config
@li @subpage overview_fs @li @subpage overview_fs
@li @subpage overview_resyn @li @subpage overview_resyntax
@li @subpage overview_arc @li @subpage overview_arc
@li @subpage overview_ipc @li @subpage overview_ipc

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///////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////
// Name: trefcount // Name: refcount.h
// Purpose: topic overview // Purpose: topic overview
// Author: wxWidgets team // Author: wxWidgets team
// RCS-ID: $Id$ // RCS-ID: $Id$
@@ -8,114 +8,117 @@
/*! /*!
@page trefcount_overview Reference counting @page overview_refcount Reference Counting
@ref refcount_overview @li @ref overview_refcount_ignore
@ref refcountequality_overview @li @ref overview_refcount_equality
@ref refcountdestruct_overview @li @ref overview_refcount_destruct
@ref refcountlist_overview @li @ref overview_refcount_list
@ref object_overview @li @ref overview_refcount_object
@section refcount Why you shouldn't care about it <hr>
Many wxWidgets objects use a technique known as @e reference counting, also known
as @e copy on write (COW).
This means that when an object is assigned to another, no copying really takes place:
only the reference count on the shared object data is incremented and both objects
share the same data (a very fast operation).
But as soon as one of the two (or more) objects is modified, the data has to be
copied because the changes to one of the objects shouldn't be seen in the
others. As data copying only happens when the object is written to, this is
known as COW.
What is important to understand is that all this happens absolutely
transparently to the class users and that whether an object is shared or not
is not seen from the outside of the class - in any case, the result of any
operation on it is the same.
@section refcountequality Object comparison
The == and != operators of @ref refcountlist_overview
always do a @c deep comparison.
This means that the equality operator will return @true if two objects are
identic and not only if they share the same data.
Note that wxWidgets follows the @e STL philosophy: when a comparison operator cannot
be implemented efficiently (like for e.g. wxImage's == operator which would need to
compare pixel-by-pixel the entire image's data), it's not implemented at all.
That's why not all reference-counted wxWidgets classes provide comparison operators.
Also note that if you only need to do a @c shallow comparison between two
#wxObject-derived classes, you should not use the == and != operators
but rather the wxObject::IsSameAs function.
@section refcountdestruct Object destruction @section overview_refcount_ignore Why You Shouldn't Care About It
When a COW object destructor is called, it may not delete the data: if it's shared, Many wxWidgets objects use a technique known as <em>reference counting</em>,
the destructor will just decrement the shared data's reference count without destroying it. also known as <em>copy on write</em> (COW). This means that when an object is
Only when the destructor of the last object owning the data is called, the data is really assigned to another, no copying really takes place. Only the reference count on
destroyed. As for all other COW-things, this happens transparently to the class users so the shared object data is incremented and both objects share the same data (a
that you shouldn't care about it. very fast operation).
But as soon as one of the two (or more) objects is modified, the data has to be
copied because the changes to one of the objects shouldn't be seen in the
others. As data copying only happens when the object is written to, this is
known as COW.
What is important to understand is that all this happens absolutely
transparently to the class users and that whether an object is shared or not is
not seen from the outside of the class - in any case, the result of any
operation on it is the same.
@section refcountlist List of reference-counted wxWidgets classes @section overview_refcount_equality Object Comparison
The following classes in wxWidgets have efficient (i.e. fast) assignment operators The == and != operators of the reference counted classes always do a @c deep
and copy constructors since they are reference-counted: comparison. This means that the equality operator will return @true if two
#wxAcceleratorTable objects are identical and not only if they share the same data.
#wxAnimation Note that wxWidgets follows the <em>STL philosophy</em>: when a comparison
operator can not be implemented efficiently (like for e.g. wxImage's ==
operator which would need to compare the entire image's data, pixel-by-pixel),
it's not implemented at all. That's why not all reference counted classes
provide comparison operators.
#wxBitmap Also note that if you only need to do a @c shallow comparison between two
#wxObject derived classes, you should not use the == and != operators but
#wxBrush rather the wxObject::IsSameAs function.
#wxCursor
#wxFont
#wxIcon
#wxImage
#wxMetafile
#wxPalette
#wxPen
#wxRegion
#wxString
#wxVariant
#wxVariantData
Note that the list above reports the objects which are reference-counted in all ports of
wxWidgets; some ports may use this tecnique also for other classes.
@section wxobjectoverview Make your own reference-counted class
Reference counting can be implemented easily using #wxObject
and #wxObjectRefData classes. Alternatively, you
can also use the #wxObjectDataPtrT template.
First, derive a new class from #wxObjectRefData and
put there the memory-consuming data.
Then derive a new class from #wxObject and implement there
the public interface which will be seen by the user of your class.
You'll probably want to add a function to your class which does the cast from
#wxObjectRefData to your class-specific shared data; e.g.:
@code
MyClassRefData *GetData() const { return wx_static_cast(MyClassRefData*, m_refData); }
@endcode
in fact, all times you'll need to read the data from your wxObject-derived class,
you'll need to call such function.
Very important, all times you need to actually modify the data placed inside your
wxObject-derived class, you must first call the wxObject::UnShare
function to be sure that the modifications won't affect other instances which are
eventually sharing your object's data.
*/
@section overview_refcount_destruct Object Destruction
When a COW object destructor is called, it may not delete the data: if it's
shared, the destructor will just decrement the shared data's reference count
without destroying it. Only when the destructor of the last object owning the
data is called, the data is really destroyed. Just like all other COW-things,
this happens transparently to the class users so that you shouldn't care about
it.
@section overview_refcount_list List of Reference Counted Classes
The following classes in wxWidgets have efficient (i.e. fast) assignment
operators and copy constructors since they are reference-counted:
@li #wxAcceleratorTable
@li #wxAnimation
@li #wxBitmap
@li #wxBrush
@li #wxCursor
@li #wxFont
@li #wxIcon
@li #wxImage
@li #wxMetafile
@li #wxPalette
@li #wxPen
@li #wxRegion
@li #wxString
@li #wxVariant
@li #wxVariantData
Note that the list above reports the objects which are reference counted in all
ports of wxWidgets; some ports may use this technique also for other classes.
@section overview_refcount_object Making Your Own Reference Counted Class
Reference counting can be implemented easily using #wxObject and
#wxObjectRefData classes. Alternatively, you can also use the
#wxObjectDataPtr<T> template.
First, derive a new class from #wxObjectRefData and put there the
memory-consuming data.
Then derive a new class from #wxObject and implement there the public interface
which will be seen by the user of your class. You'll probably want to add a
function to your class which does the cast from #wxObjectRefData to your
class-specific shared data. For example:
@code
MyClassRefData* GetData() const
{
return wx_static_cast(MyClassRefData*, m_refData);
}
@endcode
In fact, any time you need to read the data from your wxObject-derived class,
you will need to call this function.
@note Any time you need to actually modify the data placed inside your wxObject
derived class, you must first call the wxObject::UnShare function to ensure
that the modifications won't affect other instances which are eventually
sharing your object's data.
*/

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@@ -1,5 +1,5 @@
///////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////
// Name: referencenotes // Name: referencenotes.h
// Purpose: topic overview // Purpose: topic overview
// Author: wxWidgets team // Author: wxWidgets team
// RCS-ID: $Id$ // RCS-ID: $Id$
@@ -8,25 +8,24 @@
/*! /*!
@page referencenotes_overview Notes on using the reference @page overview_referencenotes Notes on Using the Reference
In the descriptions of the wxWidgets classes and their member In the descriptions of the wxWidgets classes and their member functions, note
functions, note that descriptions of inherited member functions are not that descriptions of inherited member functions are not duplicated in derived
duplicated in derived classes unless their behaviour is different. So in classes unless their behaviour is different. So in using a class such as
using a class such as wxScrolledWindow, be aware that wxWindow functions may be wxScrolledWindow, be aware that wxWindow functions may be relevant.
relevant.
Note also that arguments with default values may be omitted from a
function call, for brevity. Size and position arguments may usually be
given a value of -1 (the default), in which case wxWidgets will choose a
suitable value.
Most strings are returned as wxString objects. However, for remaining
char * return values, the strings are allocated and
deallocated by wxWidgets. Therefore, return values should always be
copied for long-term use, especially since the same buffer is often
used by wxWidgets.
The member functions are given in alphabetical order except for
constructors and destructors which appear first.
*/ Note also that arguments with default values may be omitted from a function
call, for brevity. Size and position arguments may usually be given a value of
-1 (the default), in which case wxWidgets will choose a suitable value.
Most strings are returned as wxString objects. However, for remaining char *
return values, the strings are allocated and deallocated by wxWidgets.
Therefore, return values should always be copied for long-term use, especially
since the same buffer is often used by wxWidgets.
The member functions are given in alphabetical order except for constructors
and destructors which appear first.
*/

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