X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/728449503cca147635cb0b33bfcabf5d66268f5c..4e15d1caa03346c126015019c1fdf093033ef40b:/docs/doxygen/overviews/refcount.h diff --git a/docs/doxygen/overviews/refcount.h b/docs/doxygen/overviews/refcount.h index 5feb42767e..bcddbd5e7d 100644 --- a/docs/doxygen/overviews/refcount.h +++ b/docs/doxygen/overviews/refcount.h @@ -3,24 +3,14 @@ // Purpose: topic overview // Author: wxWidgets team // RCS-ID: $Id$ -// Licence: wxWindows license +// Licence: wxWindows licence ///////////////////////////////////////////////////////////////////////////// -/*! +/** @page overview_refcount Reference Counting -@li @ref overview_refcount_ignore -@li @ref overview_refcount_equality -@li @ref overview_refcount_destruct -@li @ref overview_refcount_list -@li @ref overview_refcount_object - - -
- - -@section overview_refcount_ignore Why You Shouldn't Care About It +@tableofcontents Many wxWidgets objects use a technique known as reference counting, also known as copy on write (COW). This means that when an object is @@ -41,19 +31,20 @@ operation on it is the same. @section overview_refcount_equality Object Comparison -The == and != operators of the reference counted classes always do a @c deep -comparison. This means that the equality operator will return @true if two -objects are identical and not only if they share the same data. +The == and != operators of @ref overview_refcount_list "the reference counted classes" +always do a deep comparison. This means that the equality operator +will return @true if two objects are identical and not only if they share the +same data. Note that wxWidgets follows the STL philosophy: when a comparison -operator can not be implemented efficiently (like for e.g. wxImage's == +operator cannot 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. 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. +wxObject derived classes, you should not use the == and != operators but +rather the wxObject::IsSameAs() function. @section overview_refcount_destruct Object Destruction @@ -71,38 +62,49 @@ it. 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 +@li wxAcceleratorTable +@li wxAnimation +@li wxBitmap +@li wxBrush +@li wxCursor +@li wxFont +@li wxGraphicsBrush +@li wxGraphicsContext +@li wxGraphicsFont +@li wxGraphicsMatrix +@li wxGraphicsPath +@li wxGraphicsPen +@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. +All the objects implement a function @b IsOk() to test if they are referencing +valid data; when the objects are in uninitialized state, you can only use the +@b IsOk() getter; trying to call any other getter, e.g. wxBrush::GetStyle() on +the ::wxNullBrush object, will result in an assert failure in debug builds. + @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 template. +Reference counting can be implemented easily using wxObject or using the +intermediate wxRefCounter class directly. Alternatively, you can also use the +wxObjectDataPtr template. -First, derive a new class from #wxObjectRefData and put there the -memory-consuming data. +First, derive a new class from wxRefCounter (or wxObjectRefData when using a +wxObject derived class) and put the memory-consuming data in it. -Then derive a new class from #wxObject and implement there the public interface +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 +function to your class which does the cast from wxObjectRefData to your class-specific shared data. For example: @code @@ -116,9 +118,8 @@ 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 +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. */ -