GrafEdit - Model and presenter state access

Model and presenter state access

TStandardCanvasView has the following functions to access the model and presenter state references that cannot be overridden.

  TPresenterStateReference GetPresenterStateReference() const;
  TModelReference GetModelReference() const;

TStandardCanvasView also has the following function to access the model and presenter state instances.

  const TStandardCanvasModel* 

LookupCanvasModelForReading( TDocumentComponentReadEntry& ) const;
  const TStandardCanvasPresenterState 

LookupCanvasPresenterStateForReading( TDocumentComponentReadEntry& ) const;

These functions look up the model and presenter state, using the model and presenter state references. The presenter state is looked up with read-only access to get the current selection, and with read-write access to set the current selection. The model can only be looked up for reading to enumerate graphics and create an empty selection. All model write access should occur through commands that work on selections and not directly through the view. Each of these functions requires the caller to create and pass in an appropriate document read or write entry to assure a single thread of access in the document at one time.

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