1. In WIN8, after finish scanning, and preparing for data transferring, there is incorrect return code feedbacked. nRetCode = DSMEntry(&m_AppId, &m_DsID, DG_CONTROL, DAT_EVENT, MSG_PROCESSEVENT, (TW_MEMREF) &event);
The “TWRC_NOTDSEVENT” is always feedback. It cause app always waits for driver’s next action.
1.1 It only reproduces with TWAIN2.x(TWAINDSM.dll). It is OK with TWAIN1.x(TWAIN_32.dll).
1.2 It only reproduces in WIN8. It is OK not in XP and WIN7.
1.3 TWAINKit(TWACK) and twainapp.win32.installer.msi can get the same issue with TWAIN2.x.
2. The issue occured on most of driver, for example: EPSON S50, Brother 8860DN, HP 7650Models.
Have you tried the latest 2.2.1 DSM? It fixes a callback issue on win8. I’ve encountered the sames problem you’ve described that was resolved with this DSM.