It's cheap to store the selection position, so always set it even if we
are in a user section. Otherwise, we risk not having the right position
when starting a delete action within a begin_user_action(),
end_user_action() pair.
Related #4575
We don't want to allow new items to be grouped into a previous action
group after the end_user_action() is called. This ensures that we add a
barrier action in those conditions.
Fixes#4276
In many cases across GtkTextBuffer, we end up with operations performed
inside of a begin/end user action. Those can be coalesced into a single
sub-action within the group, and hoisted out of the group. Doing so
increases the chances that we chain similar actions together for words.
Additionally, this fixes an issue introduced in
6179886b14 for #3977 where GNOME Text Editor
started to group all possible actions into a single group.
FixesGNOME/gnome-text-editor#97
The GtkTextHistory helper provides the fundamental undo/redo stack that
can be integrated with other text widgets. It allows coalescing related
actions to reduce both the number of undo actions to the user as well as
the memory overhead.
A new istring helper is used by GtkTextHistory to allow for "inline
strings" that gracefully grow to using allocations with g_realloc(). This
ensure that most undo operations require no additional allocations other
than the struct for the action itself.
A queue of undoable and redoable actions are maintained and the link for
the queue is embedded in the undo action union. This allows again, for
reducing the number of allocations involved for undo operations.
