Added the child list to GtkCellAreaBox, added _pack_start() and
_pack_end() apis to GtkCellAreaBox since they are appropriate there
and implemented GtkCellLayoutIface to override the _pack_start()/end()
methods (since the base GtkCellArea class simply forwards these apis
to the generic ->add() api on the base class).
Now GtkCellArea handles attribute connections in the base class,
subclasses only need to add/remove the renderers, render them,
do geometry and handle events.
Now GtkCellArea provides a generic way of applying attributes
from a GtkTreeModel/GtkTreeIter, GtkCellArea bookkeeps a hashtable
of GtkCellLayoutDataFunc's and completely abstracts the applying
of data to cells... GtkCellArea implementations need only to bookkeep
the added renderers and attributes (probably we can abstract the
attribute bookkeeping in the base class as well).
Things starting to take a good and practical shape.
The scrollable patch removed set_scroll_adjustments (NULL, NULL) from
gtk_tree_view_init() which ensured the treeview would have adjustments
at all times, this patch adds set_v/hadjustment (NULL) to _init to ensure
the same thing (without it, there are crashes when trying to access the
adjustments notably from set_headers_visible() in gedit).
I.e. Since we are now calling get_preferred_width() to ensure a good 'for_size'
for get_height_for_width() we need to avoid warning about this internal expected
recursion.
These properties use GdkRGBA to render the cell renderer's content.
Note that Pango attributes are used to render the foreground color,
so the alpha value is currently ignored.
This new function takes a GdkRGBA in order to set the background to
an alpha color. Keep in mind that RGBA visuals and a composited environment
are still necessary to have an alpha background displayed.
GdkRGBA is a boxed struct similar to GdkColor, with the difference
that it stores alpha information as well, and colors are stored in
[0..1] doubles, in the cairo spirit.
gdk_cairo_set_source_rgba() has been also added to allow easier handling
of this new type.
