Instead of creating them for all items when composer window
is opened, instead just create and destroy them when
required. None are too heavy to have a noticable delay
when selecting items, but in contrast keeping them around
forever is wasteful on memory.
Also clean up a lot of duplicate composer/composition
code and remove unnecessary signals from api (use a single
itemAdded signal instead of multiple signals for every
item type)
Fixes#11371 (crash on ungrouping after moving the group) and more
undo/redo related issues.
Enable pending test for the crash (now passing) and add many more
undo/redo related ones (including signals testing).
Includes a new QgsGroupUngroupItemsCommand class
and its SIP bindings.
As per previous commit, this is useful for plugin authors. It also
fixes a potential bad crash (itemRemoved emitted for group item after
the group item was already deleted) and adds unit tests.
Previously this code was located in QgsComposerView. Moving it to
QgsComposition simplifies grouping items for plugins. Also start
a new unit test for QgsComposerItemGroup.
