There seems to be a problem with error reporting; errors from GPG (e.g., invalid password) are not coming through. I think this caused by GnuPG not reporting them correctly

Updated as requested. Only contains the core parts; C++/Qt will be uploaded separately

My concept would be to:

• add a GENKEY_EXTRAFLAG_ADDADSK for _gpgme_engine_op_genkey and gpg_genkey (or do that more implicitely, e.g., by detecting !USERID && KEY && PUBKEY) and pass the subkey fingerprint in pubkey
• use gpgme_op_createsubkey; pass the adsk fingerprint in a new variable in context

first draft is up at https://invent.kde.org/pim/libkleo/-/merge_requests/67

The Proxymodel approach seems to work; I can't find any fundamental problems due to having more rows in the proxy model than in the source model. Since this is the least invasive approach - with (almost) all changes being contained in the new model, I'm going to continue with this approach for now.

As far as I can tell, the sizeHint is "correct", for the items that are currently in the combobox. At the point in time of creating the dialog, the combobox only contains two items ("new key" and "no key"), which both have shorter strings than an average key description. The actual keys are only added to the combobox at a later point. I tried to make the dialog's size update when that happens, but have not managed to get it working yet, i think that some cache is not being invalidated correctly.

Sorry, I should have been more precise in my description of the problem. Specifically with --quick-addkey, gpg's behavior seems to be that the expiration, when given using seconds=... is treated as seconds from now.

My explanation of gpgme's behavior was not quite correct: Specifically in the QGpgMEQuickJobs for creating (sub)keys, the API uses QDateTimes, which are then converted to seconds since epoch.