# ProgressObserver

Sometimes it is desireable to display progress of current operation to user. To accomplish this task, we have implemented ProgressObserver class which implements `IObserver` (see ) and internally stores implementator of `IProgressBar` interface.

Responsibility of this class is to implement `notify` method so that current state of progress given as parameter is displayed by IProgressBar implementator. It has to recognize when progress starts (this is provided by internal flag), when it finishes (when scope's total count is reached).

Instance of this class can be registered on arbitrary descendant of `ObserverHandler` class which registers `PdfWriterObserver` This is just typedef to IObserver implementation with OperationStep template parameter. compatible observers and uses `ScopeChangeContext` with OperationStep and OperationScope template parameters.

Progress observer and related classes.