[LRC] Implement DecorationRole for all relevant objects roleData()
Issue generated from Tuleap's migration script. Originally submitted by: Emmanuel Lepage Vallee (elv13)
Currently,some models have DecorationRole (icons), but some others need to dereference the object and play with the pixmapmanipulationinterface to get them.
While dealing with icons is tricky because the actual icon "object" is dependant on the GUI toolkit (GDK pixmaps or Cairo surfaces for GTK, QIcon for Qt, etc), the API should at least be consistent on how this is handled. For now, there is no coherent way for "dumb" model bindings to display icons.
For the KDE and Windows client, Qt5 offer the QIconEngine() class that allow to create resolution independant icons.
The reason why this wasn't done sooner was the lack of "proper" research on how to handle resolution independence. After further investigation, it is not really an issue at all and can totally be implemented.