columnview: Add sorting

This is a somewhat large commit that:

- Adds GtkColumnViewSorter
This is a special-purpose, private sorter implementation which sorts
according to multiple sorters, allowing each individual sorter to be
inverted. This will be used with clickable column view headers.

- Adds a read-only GtkColumnView::sorter property
The GtkColumnView creates a GtkColumnViewSorter at startup that it uses
for this property.

- Adds a writable GtkColumnViewColumn::sorter property
This allows defining per-column sorters. Whenever an application sets a
sorter for a column, the header becomes clickable and whenever
a header is clicked, that column's sorter is prepended to the list of
sorters, unless it is already the first sorter, in which case we invert
its order. No column can be in the list more than once.

1 files changed, 3 insertions, 0 deletions

diff --git a/gtk/gtkcolumnviewcolumnprivate.h b/gtk/gtkcolumnviewcolumnprivate.h
index d7e06a5b0f..fe46663e63 100644
--- a/gtk/gtkcolumnviewcolumnprivate.h
+++ b/gtk/gtkcolumnviewcolumnprivate.h
@@ -24,6 +24,7 @@
 
 #include "gtk/gtkcolumnviewcellprivate.h"
 
+
 void                    gtk_column_view_column_set_column_view          (GtkColumnViewColumn    *self,
                                                                          GtkColumnView          *view);
 
@@ -44,4 +45,6 @@ void                    gtk_column_view_column_get_allocation           (GtkColu
                                                                          int                    *offset,
                                                                          int                    *size);
 
+void                    gtk_column_view_column_notify_sort              (GtkColumnViewColumn    *self);
+
 #endif  /* __GTK_COLUMN_VIEW_COLUMN_PRIVATE_H__ */