\hypertarget{classHurricane_1_1UpdateSession}{}\section{Hurricane\+:\+:Update\+Session Class Reference}
\label{classHurricane_1_1UpdateSession}\index{Hurricane\+::\+Update\+Session@{Hurricane\+::\+Update\+Session}}


\mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}} description ({\bfseries A\+PI})  




Inheritance diagram for Hurricane\+:\+:Update\+Session\+:\nopagebreak
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\subsection*{Additional Inherited Members}


\subsection{Detailed Description}
\mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}} description ({\bfseries A\+PI}) 

\hypertarget{classHurricane_1_1UpdateSession_secUpdateSessionMechanism}{}\subsection{Update Session Mechanism}\label{classHurricane_1_1UpdateSession_secUpdateSessionMechanism}
Here is only an outline of the \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}} mechanism. The classes involved are\+:
\begin{DoxyItemize}
\item \mbox{\hyperlink{classHurricane_1_1Go}{Go}} (Graphical Objects and their sub-\/classes).
\item \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}} and it\textquotesingle{}s Quad\+Tree(s). Note that the \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}} is {\itshape not} a \mbox{\hyperlink{classHurricane_1_1Go}{Go}}.
\item \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}}.
\end{DoxyItemize}

When a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} is to be displayed, it has to be inserted inside one of the \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}} of it\textquotesingle{}s owner \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}}. \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}} allows fast geometric queries which are used extensively to perform the display. If a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} is {\bfseries not} inserted in a \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}} it will {\bfseries not} be displayed at all or be included in any geometric query. When we insert a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} in a \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}}, we talk about {\bfseries materialization}. So a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} can be in two states\+: {\bfseries materialized} or {\bfseries unmaterialized}. The default behavior is to materialize a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} as soon as it is created.

Now comes the \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}} mechanism. When the characteristics of a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} are changed, it may be needed to update it\textquotesingle{}s position inside the \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}}, or even to change of \mbox{\hyperlink{classHurricane_1_1QuadTree}{Quad\+Tree}} (in case of a \mbox{\hyperlink{classHurricane_1_1Layer}{Layer}} change). Basically, the mechanism proceed in three stages\+:


\begin{DoxyItemize}
\item Start a new \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}} (it\textquotesingle{}s a \mbox{\hyperlink{classHurricane_1_1SharedProperty}{Shared\+Property}}).
\item When a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} is changed, the {\ttfamily invalidate()} method is called, that {\itshape unmaterialize()} it, then adds it to the current \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}}. This is done by adding the \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}}, as a property, to the \mbox{\hyperlink{classHurricane_1_1Go}{Go}}. The \mbox{\hyperlink{classHurricane_1_1Go}{Go}} owner (it\textquotesingle{}s \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}}) is also notified a {\ttfamily Cell\+::\+Flags\+::\+Cell\+About\+To\+Change}.
\item On closing the \mbox{\hyperlink{classHurricane_1_1UpdateSession}{Update\+Session}}, all the stored Gos are {\bfseries materialized} again. The owner \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}} and their instances are then send a notification {\ttfamily Cell\+::\+Flags\+::\+Cell\+Changed}.
\end{DoxyItemize}

It is very important to notice that the Cells gets change notifications only when a \mbox{\hyperlink{classHurricane_1_1Go}{Go}} is {\itshape changed}, not when it is {\itshape created}. If we want the \mbox{\hyperlink{classHurricane_1_1Cell}{Cell}} to be notified, we must invalidate it manually. This is particularly critical when working with Extension\+Go. 

The documentation for this class was generated from the following file\+:\begin{DoxyCompactItemize}
\item 
Update\+Session.\+h\end{DoxyCompactItemize}
