scanner hangs when no paper is feeded for NoUI

[alpha berrie]

I was trying to run the provided NTwainTest (By default, the UI was supressed). If no paper is feeded, then the scanner just doesn't respond for a long time. I just wonder if there is any way to detect the paper is feeded or not before I can start scan.

[Eugene Wang]

If supported by the driver, you can use Capabilities.CapFeederLoaded.GetCurrent() on the DataSource.

[Keith Platter]

I was having this issue as well, and was able to use the CapFeederLoaded and CapPaperDetectable to get around this issue. However I was looking for a way to handle other data source UI components that may open and block the scanning process when the UI is suppressed.
I was able to hook the window creation messages and get notification of windows being created on the process, but I am unable to close the windows if they remain open because I can not send a destroy message since it is on another thread. Is it safe to just close the Datasource or Session if it remains open/enabled for a length of time (via timer)? Is their an example of using the SynchronizationContext to have the ui on the same thread?

[Eugene Wang]

You should be able to use pass a WindowsFormsMessageLoopHook or WpfMessageLoopHook object when calling TwainSession.Open() to have it run on the UI thread.