Hurricane::UpdateSession Class Reference

UpdateSession description (API). More...

Inheritance diagram for Hurricane::UpdateSession:

Additional Inherited Members

Public Member Functions inherited from Hurricane::Property

Detailed Description

UpdateSession description (API).

Update Session Mechanism

Here is only an outline of the UpdateSession mechanism. The classes involved are:

• Go (Graphical Objects and their sub-classes).
• Cell and it's QuadTree(s). Note that the Cell is not a Go.
• UpdateSession.

When a Go is to be displayed, it has to be inserted inside one of the QuadTree of it's owner Cell. QuadTree allows fast geometric queries which are used extensively to perform the display. If a Go is not inserted in a QuadTree it will not be displayed at all or be included in any geometric query. When we insert a Go in a QuadTree, we talk about materialization. So a Go can be in two states: materialized or unmaterialized. The default behavior is to materialize a Go as soon as it is created.

Now comes the UpdateSession mechanism. When the characteristics of a Go are changed, it may be needed to update it's position inside the QuadTree, or even to change of QuadTree (in case of a Layer change). Basically, the mechanism proceed in three stages:

• Start a new UpdateSession (it's a SharedProperty).
• When a Go is changed, the invalidate() method is called, that unmaterialize() it, then adds it to the current UpdateSession. This is done by adding the UpdateSession, as a property, to the Go. The Go owner (it's Cell) is also notified a Cell::Flags::CellAboutToChange.
• On closing the UpdateSession, all the stored Gos are materialized again. The owner Cell and their instances are then send a notification Cell::Flags::CellChanged.

It is very important to notice that the Cells gets change notifications only when a Go is changed, not when it is created. If we want the Cell to be notified, we must invalidate it manually. This is particularly critical when working with ExtensionGo.

---

The documentation for this class was generated from the following file:

• UpdateSession.h