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InvisibleApp.MustFlushScopeBeginning Event (Visio)

Occurs before the Microsoft Visio instance is forced to flush its event queue.

Version Added: Visio 5.0

Private Sub expression _MustFlushScopeBeginning(ByVal app As [IVAPPLICATION])

expression A variable that represents an InvisibleApp object.

Parameters

Name

Required/Optional

Data Type

Description

app

Required

[IVAPPLICATION]

The instance of Visio that is forced to flush its event queue.

This event, along with the MustFlushScopeEnded event, can be used to identify whether an event is being fired because Visio is forced to flush its event queue.

Visio maintains a queue of pending events that it attempts to fire at discrete moments when it is able to process arbitrary requests (callbacks) from event handlers.

Occasionally, Visio is forced to flush its event queue when it is not prepared to handle arbitrary requests. When this occurs, Visio first fires a MustFlushScopeBeginning event, and then it fires the events that are presently in its event queue. After firing all pending events, Visio fires the MustFlushScopeEnded event.

After Visio has fired the MustFlushScopeBeginning event, client programs should not call Visio methods that have side effects until the MustFlushScopeEnded event is received. A client can perform arbitrary queries of Visio objects when Visio is between the MustFlushScopeBeginning event and MustFlushScopeEnded event, but operations that cause side effects may fail.

Visio performs a forced flush of its event queue immediately prior to firing a "before" event such as BeforeDocumentClose or BeforeShapeDelete because queued events may apply to objects that are about to close or be deleted. Using the BeforeDocumentClose event as an example, there can be queued events that apply to a shape object in the document that is being closed. So, before the document closes, Visio fires all the events in its event queue.

When a shape is deleted, events are fired in the following sequence:

  1. MustFlushScopeBeginning event
    Client should not call methods that have side effects.

  2. There are zero (0) or more events in the event queue.

  3. BeforeShapeDelete event
    Shape is viable, but Visio is going to delete it.

  4. MustFlushScopeEnded event
    Client can resume invoking methods that have side effects.

  5. ShapesDeleted event
    Shape has been deleted.

  6. NoEventsPending event
    No events remain to be fired.

An event is fired both before (BeforeShapeDeleted event) and after (ShapesDeleted event) the shape is deleted. If a program monitoring these events requires that additional shapes be deleted in response to the initial shape deletion, it should do so in the ShapesDeleted event handler, not the BeforeShapeDeleted event handler. The BeforeShapeDeleted event is inside the scope of the MustFlushScopeBeginning event and the MustFlushScopeEnded event, while the ShapesDeleted event is not.

The sequence number of a MustFlushScopeBeginning event may be higher than the sequence number of events the client sees after it has received the MustFlushScopeBeginning event because Visio assigns sequence numbers to events as they occur. Any events that were queued when the forced flush began have a lower sequence number than the MustFlushScopeBeginning event, even though the MustFlushScopeBeginning event fires first.

If you're using Microsoft Visual Basic or Visual Basic for Applications (VBA), the syntax in this topic describes a common, efficient way to handle events.

If you want to create your own Event objects, use the Add or AddAdvise method. To create an Event object that runs an add-on, use the Add method as it applies to the EventList collection. To create an Event object that receives notification, use the AddAdvise method. To find an event code for the event you want to create, see Event codes.

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