Regression in support of duplex ADF

[aaliddell]

Since 1.5.0, specifically commit db44b39, an incorrect scan height is sent when using a duplex ADF and no manual height is specified on the command line. Prior to this release, if no height was set, it would send 3507 by default and this would succeed for all scan types (ADF, no ADF, duplex ADF). Since this release, ADF and platen work, but duplex ADF failes with 409 conflict as the height is too large (sends 4200).

This fails because you are sending the MaxHeight from the InputSourceCaps when using the ADF, which is correct for simplex but for duplex you must use AdfDuplexer/AdfDuplexMaxHeight, which is a smaller number (3508). This quick workaround is to set the height CLI flag, but this should be set correctly based on the values from the printer.

I will look into sending a PR shortly.