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IViewObject Interface

IID_IViewObject

{0000010D-0000-0000-C000-000000000046}

The

IViewObject

interface enables an object to display itself directly without passing a data object to the caller. In addition, this interface can create and manage a connection with an advise sink so the caller can be notified of changes in the view object.

The caller can request specific representations and specific target devices. For example, a caller can ask for either an object’s content or an iconic representation. Also, the caller can ask the object to compose a picture for a target device that is independent of the drawing device context. As a result, the picture can be composed for one target device and drawn on another device context. For example, to provide a print preview operation, you can compose the drawing for a printer target device but actually draw the representation on the display.

The

IViewObject

interface is similar to

IDataObject

; except that

IViewObject

places a representation of the data onto a device context while

IDataObject

places the representation onto a transfer medium.

Unlike most other interfaces,

IViewObject

cannot be marshaled to another process. This is because device contexts are only effective in the context of one process.

You call

IViewObject

from a container application if you need to draw a contained object on a specific device context. For example, if you want to print the object to a printer, you call the

Draw

method in the

IViewObject

interface.

Methods in VTable order
IUnknown Methods	Description
QueryInterface	Returns pointers to supported interfaces.
AddRef	Increments reference count.
Release	Decrements reference count.
IViewObject Methods	Description
Draw	Draws a representation of the object onto a device context.
GetColorSet	Returns the logical palette the object uses for drawing.
Freeze	Freezes the drawn representation of an object so it will not change until a subsequent Unfreeze .
Unfreeze	Unfreezes the drawn representation of an object.
SetAdvise	Sets up a connection between the view object and an advise sink so that the advise sink can receive notifications of changes in the view object.
GetAdvise	Returns the information on the most recent SetAdvise .

出处:http://www.com.it-berater.org/COM/ole_and_data_transfer/interfaces/IViewObject.htm