Description
Determines whether the Image, Overlays or Both are included in the generated Display.
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Property type
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A mcDisplayWhat enumeration.
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Syntax
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object.DisplayWhat [= value]
The DisplayWhat Property syntax has these parts:
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| object | An expression evaluating to an object of type McDisplay. |
| value | A mcDisplayWhat enumeration, as described in settings. |
Settings
The settings for value are:
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 | mcdwDisplayNone | 0 |
Neither overlays nor image are displayed. This will rarely be useful.
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| mcdwImageOnly | 1 |
Only the image is displayed. No overlay clients are given an opportunity to paint.
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| mcdwOverlaysOnly | 2 |
No image display is done. The display is initialized to black and then overlay clients are allowed to paint.
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| mcdwBothImageAndOverlays | 3 |
Both image and overlays display. The image is painted first and then the overlay clients are allowed to paint.
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Remarks
When DisplayWhat is not mcdwImageOnly or mcdwBothImageAndOverlays, then the viewer blackens the target display surface and doesn't display the image. However, the viewer's PostPaint event is still fired, allowing the overlays to paint onto the display surface.
Assigning mcdwImageOnly or mcdwImageOnly will prevent AboutToPaint and PostPaint being sent to all notify clients, thereby removing all overlay painting from the image. Individual overlays may be turned off via the NotifyEnabled property, and their notify order may be changed via the SetNotifyPriority method.
Notes
This property is sometimes useful for improving performance by stopping image display even when you want to eventually display the image, especially if the image will undergo a multitude of interim changes during an involved process. Another possible use is if the display window is subclassed, perhaps by a capture driver. The subclassing code could then implement some specialized display code with out worrying about the viewer interfering.
DisplayWhat Property
