Transparent Picture Control Quirks?

Question

(cross-posted to LAVA)
Can anyone explain this?
A Picture Control that has been painted transparent has a different Erase First behavior in the context menu.
Regular picture control, dropped right off the palettes:
Note that the Erase First item is enabled, and checked by default.
But, if we use the paintbrush to paint the interior of the Picture Control transparent and then bring up the context menu again:
Note that now Erase First is checked and disabled so it cannot be unchecked.
But there's more.  If you try to set the Erase First behavior programmatically, LabVIEW doesn't generate an error and seems to accept the setting, but the change isn't reflected in the context menu:
It also appears that, regardless of the behavior shown, a Picture Control that's been painted transparent ignores all programmatic Erase First settings and behaves as though it's set to Always Erase.  This, in turn, means that if you set a Picture Control's background to transparent, it will always tend to flicker as you draw more stuff to it, unless you take special precautions (like deferring panel updates).
Why does a transparent-background Picture Control behave differently from a Picture Control with an opaque background?
Message Edited by Justin J. Goeres on 12-01-2008 02:30 PM

Answer 1

Since;
1) Justin is used to the "Dark-side" and
2)all picture related question interest me
3) And NI does not answer Q's on LAVA I will help out a bit. The following is what I think Justin wanted us to see,
Justin J. Goeres wrote:
(cross-posted to LAVA)
Can anyone explain this?
A Picture Control that has been painted transparent has a different Erase First behavior in the context menu.
Regular picture control, dropped right off the palettes:
Note that the Erase First item is enabled, and checked by default.
But, if we use the paintbrush to paint the interior of the Picture Control transparent and then bring up the context menu again:
Note that now Erase First is checked and disabled so it cannot be unchecked.
But there's more.  If you try to set the Erase First behavior programmatically, LabVIEW doesn't generate an error and seems to accept the setting, but the change isn't reflected in the context menu:
It also appears that, regardless of the behavior shown, a Picture Control that's been painted transparent ignores all programmatic Erase First settings and behaves as though it's set to Always Erase.  This, in turn, means that if you set a Picture Control's background to transparent, it will always tend to flicker as you draw more stuff to it, unless you take special precautions (like deferring panel updates).
Why does a transparent-background Picture Control behave differently from a Picture Control with an opaque background?
Message Edited by Justin J. Goeres on 12-01-2008 02:30 PM
Message Edited by Ben on 12-01-2008 04:05 PM (eastern US)
Ben
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