If blnCancel Then

' If the client is tired of waiting and wants the task canceled, raise the Complete event with True (canceled).

RaiseEvent Complete(True)

Exit Sub

End If

sngNextMark = sngNextMark + 0.1!

End If

Next

' On successful completion, raise the Complete event with False (not canceled).

RaiseEvent Complete(False)

End Sub

Coffee.Cls Option Explicit Private Declare Function timeGetTime Lib "winmm.Dll" () As Long

' The Coffee object represents a different style of asynchronous notifications from those performed by the CoffeeMonitors. Instead of periodic notifications Coffee provides progress reports on a long task, and a completion event.

'

' The mechanism used for these notifications is to raise events. You could also use call-back methods, and in fact there are advantages to doing so. Call-backs would allow a component to deal intelligently with errors in the client, whereas events don't return client errors. This is discussed in "When to Use Events or Call-Backs for Notifications," in Books Online.

' Number of iterations to perform in the dummy task.

Private mlngIterations As Long

' XTimer is used to kick the long task off asynchronously.

Private WithEvents mwXTimer As XTimer

Event Progress(ByVal PercentDone As Single, ByRef Cancel As Boolean)

Event Complete(ByVal Canceled As Boolean)

' ThreadID returns the system thread ID of the thread the object was created on.

'

Public Property Get ThreadID() As Long

ThreadID = App.ThreadID

End Property

' NumberOnThread returns the number of Coffee objects running on this thread. This is just the value of the global data variable glngGlobalData, which Coffee objects increment in their Initialize events and decrement in their Terminate events.

' If MTCoffee was compiled with Thread Per Object, the only way for multiple objects' to share a thread (and the instance of global data associated with it) is if another Coffee has been created on this thread by calling GetCoffeeOnSameThread.

' If MTCoffee was compiled with a Thread Pool and the count of active objects exceeded the number of threads in the pool, then Coffee objects will be sharing threads.

'

Public Property Get NumberOnThread() As Long

NumberOnThread = glngGlobalData

End Property

' StartLongTask sets things up for the long dummy task. The task is actually started by a code-only XTimer that StartLongTask sets running.

'

Public Sub StartLongTask(ByVal Iterations As Long)

' This is a short circuit for testing call overhead. See CallAnotherCoffee.

If Iterations = 0 Then Exit Sub

'

' Store the size of the dummy task.

mlngIterations = Iterations

'

' Give the timer a short interval, and set it running just before returning.

mwXTimer.Interval = 55

mwXTimer.Enabled = True

End Sub

' GetCoffeeOnSameThread creates a new Coffee object on the same thread, simulating the effects of thread pooling. This can only be done internally, as explained in "How Object Creation Works in Visual Basic" in Books Online.

'

Public Function GetCoffeeOnSameThread() As Coffee

' All objects created using New will be on

' the creator's thread, even a new

' Coffee object.

Set GetCoffeeOnSameThread = New Coffee

End Function

' GetCoffeeOnNewThread creates a new Coffee object on a new thread, by calling CreateObject to create the new Coffee object. The difference between this and the internal creation done by GetCoffeeOnSameThread is explained in "How Object Creation Works in Visual Basic" in Books Online.'

' Note that this technique could be used to create objects on different threads that could communicate with each other, without the client having to pass one object a reference to the other (as CoffeeWatch does). If you experiment with this, remember that the overhead of marshaling calls between threads is almost as great as the overhead of marshaling calls across processes.

'