forked from AuroraMiddleware/gtk
93 lines
2.6 KiB
Plaintext
93 lines
2.6 KiB
Plaintext
How ref counting works within Gdk and Gtk
|
|
=========================================
|
|
|
|
Each data structure that provides ref counting offers a bunch of
|
|
functions that follow these conventions:
|
|
|
|
*_new: Create a new structure with a reference count of 1.
|
|
*_ref: Increase ref count by one.
|
|
*_unref: Decrease ref count by one. If the count drops to zero,
|
|
free the memory. No user visible actions should take place,
|
|
like destryoing windows, etc.
|
|
|
|
Some structures also provide a *_destroy function.
|
|
|
|
GdkWindow
|
|
---------
|
|
|
|
A GdkWindow has to be explicitely destroyed with gdk_window_destroy.
|
|
This will send out a request to destroy this window and all its
|
|
children, and will decrement the ref_count of the GdkWindow by one.
|
|
Thus, it releases the inital reference created by gdk_window_new.
|
|
|
|
All GdkWindows are kept in a hash table to translate from their XId to
|
|
the actual structure and the pointer in the hash table is reflected in
|
|
the reference count. When a DestroyNotify event is received for a
|
|
particular GdkWindow, it is removed from the hash table and the
|
|
ref_count is updated accordingly.
|
|
|
|
You can call gdk_window_destroy more than once on a particular
|
|
GdkWindow, it will only be destroyed when it hasn't been yet. The
|
|
ref_count is *always* decremented, tho.
|
|
|
|
GdkPixmap
|
|
---------
|
|
|
|
There is no gdk_pixmap_destroy function. The Pixmap is destroyed when
|
|
the last reference to it vanishes.
|
|
|
|
GdkPixmaps are kept in the same hash table as GdkWindows but the
|
|
pointer in the hash table is *not* reflected in the ref_count.
|
|
|
|
This works only when Pixmaps never get XEvents. I'm not sure if this
|
|
is the case.
|
|
|
|
GdkBitmap
|
|
---------
|
|
|
|
A GdkBitmap is only another name for a special use of GdkPixmap.
|
|
|
|
GdkVisual
|
|
---------
|
|
|
|
There are no *_new or *_destroy functions and the *_ref and *_unref
|
|
functions are noops. GdkVisuals are static structures and thus do not
|
|
need reference counting. The ref counting functions are only there
|
|
for extra defensive programming.
|
|
|
|
GdkColormap
|
|
-----------
|
|
|
|
Nothing special. There is no gdk_colormap_destroy function.
|
|
|
|
GdkFont / GdkFontSet
|
|
--------------------
|
|
|
|
GdkFont and GdkFontSet are equivalent as far as ref counting is
|
|
concerned. Use gdk_font_ref and gdk_font_unref for both.
|
|
|
|
There is no gdk_font_free or gdk_fontset_free function.
|
|
|
|
GtkAcceleratorTable
|
|
-------------------
|
|
|
|
There is no gtk_accelerator_table_destroy function.
|
|
|
|
GtkTooltips
|
|
-----------
|
|
|
|
There is no gtk_tooltips_destroy function.
|
|
|
|
GtkStyle
|
|
--------
|
|
|
|
There is no gtk_style_destroy function.
|
|
|
|
GtkObject
|
|
---------
|
|
|
|
This one is the most tricky and I'm still meditating over it.
|
|
|
|
|
|
- Marius Vollmer <mvo@zagadka.ping.de>
|