Attribute and Item Views

Most of the Qt subsytem is dedicated to providing users with ways to create, delete, and modify attributes. There are two Qt-specific subclasses of smtk::view::BaseView dedicated to this:

• smtk::extension::qtInstancedView is a view dedicated to displaying and editing a single, named instance of an attribute.

• smtk::extension::qtAttributeView is a view dedicated to creating, destroying, and editing any number of attributes that share some common base definition (such as a material or boundary condition).

Each of these views inherits smtk::extension::qtBaseAttributeView and displays items of the attribute.

Items displayed inside these views all inherit smtk::extension::qtItem.

Qt view classes also provide facilities that adapt SMTK’s Observers to Qt’s signals-and-slots system. When an item indicates it has modified its parent attribute (via a Qt signal), the view creates and launches a smtk::attribute::Signal operation to notify core SMTK objects of the change. Thus, if you are implementing a custom Qt item class, you should emit a modified() signal; the parent attribute-view will consume this signal and run the operation for you.

Likewise, subclasses of :smtk::extension::qtItem should not observe SMTK operations themselves but instead rely on the Qt subsystem to observe operations. Each time an operation completes, the Qt view observes it and calls the updateItemData() on each of its attributes’ items.