The gdk-pixbuf Library gdk-pixbuf-gdk-pixbuf.html<<< Previous Page index.htmlHome r27.htmlUp gdk-pixbuf-file-loading.htmlNext Page >>> Reference Counting and Memory Mangement
Name
Reference Counting and Memory Mangement -- Functions to perform reference counting and memory management on a
GdkPixbuf.
Synopsis

#include <gdk-pixbuf/gdk-pixbuf.h>
void        (
gdk-pixbuf-refcounting.html#GDKPIXBUFDESTROYNOTIFY*GdkPixbufDestroyNotify )       (guchar *pixels,
                                             gpointer data);
void        (
gdk-pixbuf-refcounting.html#GDKPIXBUFLASTUNREF*GdkPixbufLastUnref )           (GdkPixbuf *pixbuf,
                                             gpointer data);
GdkPixbuf*  
gdk-pixbuf-refcounting.html#GDK-PIXBUF-REFgdk_pixbuf_ref                   (GdkPixbuf *pixbuf);
void        
gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREFgdk_pixbuf_unref                 (GdkPixbuf *pixbuf);
void        
gdk-pixbuf-refcounting.html#GDK-PIXBUF-SET-LAST-UNREF-HANDLERgdk_pixbuf_set_last_unref_handler                                             (GdkPixbuf *pixbuf,
                                             
gdk-pixbuf-refcounting.html#GDKPIXBUFLASTUNREFGdkPixbufLastUnref  last_unref_fn,
                                             gpointer last_unref_fn_data);
void        
gdk-pixbuf-refcounting.html#GDK-PIXBUF-FINALIZEgdk_pixbuf_finalize              (GdkPixbuf *pixbuf); Description
    GdkPixbuf structures are reference counted.  This means that
    an application can share a single pixbuf among many parts of the
    code.  When a piece of the program needs to keep a pointer to a
    pixbuf, it should add a reference to it.  When it no longer needs
    the pixbuf, it should subtract a reference.  The pixbuf will be
    destroyed when its reference count drops to zero.  Newly-created
    GdkPixbuf structures start with a reference count of one.
  
    Finalizing a pixbuf means to free its pixel
    data and to free the GdkPixbuf structure itself.  Most of the
    library functions that create GdkPixbuf structures create the
    pixel data by themselves and define the way it should be freed;
    you do not need to worry about those.  The only function that lets
    you specify how to free the pixel data is
    
gdk-pixbuf-creating.html#GDK-PIXBUF-NEW-FROM-DATAgdk_pixbuf_new_from_data ().  Since you pass it a pre-allocated
    pixel buffer, you must also specify a way to free that data.  This
    is done with a function of type 
gdk-pixbuf-refcounting.html#GDKPIXBUFDESTROYNOTIFYGdkPixbufDestroyNotify .  When a
    pixbuf created with 
gdk-pixbuf-creating.html#GDK-PIXBUF-NEW-FROM-DATAgdk_pixbuf_new_from_data () is finalized, your
    destroy notification function will be called, and it is its
    responsibility to free the pixel array.
  
    As an extension to traditional reference counting, GdkPixbuf
    structures support defining a handler for the last unref
    operation.  If 
gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREFgdk_pixbuf_unref () is called on a GdkPixbuf
    structure that has a reference count of 1, i.e. its last
    reference, then the pixbuf's last unref handler function will be
    called.  It is up to this function to determine whether to
    finalize the pixbuf using 
gdk-pixbuf-refcounting.html#GDK-PIXBUF-FINALIZEgdk_pixbuf_finalize () or to just
    continue execution.  This can be used to implement a pixbuf cache
    efficiently; please see the programmer's documentation for
    details.
  
Details
GdkPixbufDestroyNotify ()
void        (*GdkPixbufDestroyNotify)       (guchar *pixels,
                                             gpointer data);
    A function of this type is responsible for freeing the pixel array
    of a pixbuf.  The 
gdk-pixbuf-creating.html#GDK-PIXBUF-NEW-FROM-DATAgdk_pixbuf_new_from_data () function lets you
    pass in a pre-allocated pixel array so that a pixbuf can be
    created from it; in this case you will need to pass in a function
    of 
gdk-pixbuf-refcounting.html#GDKPIXBUFDESTROYNOTIFYGdkPixbufDestroyNotify  so that the pixel data can be freed
    when the pixbuf is finalized.
  
pixels : The pixel array of the pixbuf that is being finalized. data : User closure data.

GdkPixbufLastUnref ()
void        (*GdkPixbufLastUnref)           (GdkPixbuf *pixbuf,
                                             gpointer data);
    A function of this type can be used to override the default
    operation when a pixbuf loses its last reference, i.e. when
    
gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREFgdk_pixbuf_unref () is called on a GdkPixbuf structure that has a
    reference count of 1.  This function should determine whether to
    finalize the pixbuf by calling 
gdk-pixbuf-refcounting.html#GDK-PIXBUF-FINALIZEgdk_pixbuf_finalize (), or whether
    to just resume normal execution.  The last unref handler for a
    GdkPixbuf can be set using the
    
gdk-pixbuf-refcounting.html#GDK-PIXBUF-SET-LAST-UNREF-HANDLERgdk_pixbuf_set_last_unref_handler () function.  By default, pixbufs
    will be finalized automatically if no last unref handler has been
    defined.
  
pixbuf : The pixbuf that is losing its last reference. data : User closure data.

gdk_pixbuf_ref ()
GdkPixbuf*  gdk_pixbuf_ref                  (GdkPixbuf *pixbuf); Adds a reference to a pixbuf.  It must be released afterwards using
gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREFgdk_pixbuf_unref ().

  
pixbuf :  A pixbuf. Returns :  The same as the pixbuf argument. 
gdk_pixbuf_unref ()
void        gdk_pixbuf_unref                (GdkPixbuf *pixbuf); Removes a reference from a pixbuf.  If this is the last reference for the
pixbuf, then its last unref handler function will be called; if no handler
has been defined, then the pixbuf will be finalized.
See also: gdk-pixbuf-refcounting.html#GDK-PIXBUF-SET-LAST-UNREF-HANDLERgdk_pixbuf_set_last_unref_handler ().
pixbuf :  A pixbuf. 
gdk_pixbuf_set_last_unref_handler ()
void        gdk_pixbuf_set_last_unref_handler
                                            (GdkPixbuf *pixbuf,
                                             
gdk-pixbuf-refcounting.html#GDKPIXBUFLASTUNREFGdkPixbufLastUnref  last_unref_fn,
                                             gpointer last_unref_fn_data);
Sets the handler function for the pixbuf's last unref handler.  When
gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREFgdk_pixbuf_unref () is called on this pixbuf and it has a reference count of
1, i.e. its last reference, then the last unref handler will be called.  This
function should determine whether to finalize the pixbuf or just continue.
If it wishes to finalize the pixbuf, it should do so by calling
gdk-pixbuf-refcounting.html#GDK-PIXBUF-FINALIZEgdk_pixbuf_finalize ().
See also: gdk-pixbuf-refcounting.html#GDK-PIXBUF-FINALIZEgdk_pixbuf_finalize ().
pixbuf :  A pixbuf. last_unref_fn :  Handler function for the last unref. last_unref_fn_data :  Closure data to pass to the last unref handler function. 
gdk_pixbuf_finalize ()
void        gdk_pixbuf_finalize             (GdkPixbuf *pixbuf); Finalizes a pixbuf by calling its destroy notification function to free the
pixel data and freeing the pixbuf itself.  This function is meant to be
called only from within a 
gdk-pixbuf-refcounting.html#GDKPIXBUFLASTUNREFGdkPixbufLastUnref  handler function, and the
specified 
pixbuf must have a reference count of 1, i.e. its last reference.
pixbuf :  A pixbuf with a reference count of 1. 
See Also
    GdkPixbuf, gdk-pixbuf-creating.html#GDK-PIXBUF-NEW-FROM-DATAgdk_pixbuf_new_from_data ().
  
gdk-pixbuf-gdk-pixbuf.html<<< Previous Page index.htmlHome r27.htmlUp gdk-pixbuf-file-loading.htmlNext Page >>> The GdkPixbuf Structure File Loading 