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Topic: Screenshot of hidden panel with ActiveX

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skafoelix
Newbie
Newbie

Joined: July 15 2009
Location: Germany
Posts: 2

Posted: July 15 2009 at 2:26am \| IP Logged

Hi!

I'm currently looking for a good Docking Library and I like yours a lot.
But I have a very specific requirement which none of the currently available libraries, including yours seem to support.

I need to be able to take a screenshots of all tabs in a container including those that are not visible.
This by itself is not a problem and can simply be done by calling the DrawToBitmap method which every System.Windows.Forms.Control supports. But the problems start to occur when using ActiveX controls on those tabs which I make extensive use of. The DrawToBitmap method doesn't support ActiveX controls. There's simply a white rectangle in place of the control.

There are methods available in the WinAPI which support taking screenshots of Windows that are not visible and it doesn't matter what controls are on the Window. The PrintWindow http://www.pinvoke.net/default.aspx/user32/PrintWindow.html function for example supports that. But it doesn't work with your library. If I try to use it on a control hosted in a DockContainer I just get a black image.

So my question is, do you know of a way to take screenshots of all the tabs hosted in a DockContainer including those with ActiveX controls?
Or is this something you could implement in your library?

As much as I would love to use your library I can't do without the functionality.

Thx for your time.
Felix

Klik! Support
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Joined: October 01 2003
Location: Turkey
Posts: 313

Posted: July 15 2009 at 2:40am \| IP Logged

Hello Felix,

Thank you very much for your interest first of all...

The feature you request is actually not related with our library which I'm sure you'll agree. We did a quick search and found out that DrawToBitmap and PrintWindow functions are actually sending WM_PRINT message to the window that you are taking the screenshot and again it seems that most (or maybe all) of the ActiveX controls do not implement that message or do not receive it thus you are getting a black rectangle as a result.

I'm afraid that we don't have any workaround for that case and it seems that your only solution is to make them visible and take a screenshot as usual.

Sorry for not being able to help in that case and please let us know if you have any further questions...

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Best Regards,

Klik! Support Team

skafoelix
Newbie
Newbie

Joined: July 15 2009
Location: Germany
Posts: 2

Posted: July 15 2009 at 3:43am \| IP Logged

Yeah, I agree that it's not directly related to your library.

Well, the problem with PrintWindow is different to the DrawToBitmap problem.
When I use DrawToBitmap the resulting image contains every control that is hosted in the container but any ActiveX control will be displayed just as a white rectangle. No matter if the tab is active or not.
When I use PrintWindow on the active tab it contains every control including ActiveX controls. Perfect! But when I try to use it on a not-active tab the whole image comes out black. No matter if there's an ActiveX control or not.

So there seems to be a difference in the two functions. If I could combine those two, the output would be perfect.

I ask you because if you could implement this functionality into your library you'd have something none of the other libraries have. So you create a new window class that when hosted in one of your tab containers could display the content of all the tabs. Just like in IE8, Opera or Safari.

Klik! Support
Admin Group

Joined: October 01 2003
Location: Turkey
Posts: 313

Posted: July 15 2009 at 4:22am \| IP Logged

Hello Felix,

Ah, yes, probably, the PrintWindow API uses the same way as capturing the visible objects in screen.

I'm afraid there is not much we can do as we are bound with exposed windows functions as everbody else does.

Sorry again.

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Klik! Support Team

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