Add a new read-only GimpToolItem::shown property, and a
corresponding GimpToolItem::shown-changed signal, which determines
if a tool item is visible throughtout the hierarchy, i.e., if it
and all its ancestors are visible. This replaces
gimp_tool_item_is_visible().
Use the new property and signal in GimpToolPalette and
GimpToolEditor, to simplify the code, and in preparation for a flat
toolbox view.
(cherry picked from commit ee9661237e)
In GimpToolManager, use a weak pointer for tracking the active tool
group, instead of taking a reference on it. This avoids
erroneously extending the group's lifetime, which can cause
problems with the tool-item hierarchy.
In GimpToolGroup, make sure that newly-added tools don't already
have a parent.
(cherry picked from commit 30d833d00f)
Add GimpToolGroup as a new subclass of GimpToolItem, representing a
collection of tools. The end goal is to display tool groups using
a single button in the toolbox.
Tool groups are not recursive: they can only contain individual
tools, not other groups. Each group has a single "active tool",
normally the most-recently-used tool of the group, which is
activated when clicking on the tool's button.
