64-Bit Windows applications typically expect the Twain Data Source manager to be named twaindsm.dll.
Send the DG_CONTROL/DAT_ENTRYPOINT/MSG_SET before DG_CONTROL/DAT_IDENTITY/MSG_OPENDS so sane.ds does not need to know the module name to find the DSM entry point.
An explanation for the request to offer the name twaindsm.dll for 64-Bit windows is offered here by the TWAIN organization:
https://github.com/twain/twain-dsm/blob/master/TWAIN_DSM/src/readme.doc
They cannot update the twain_32.dll installed and maintained by Microsoft, so they choose the new name twaindsm.dll instead. This name is also used at least by Irfanview and oder versions oder LibreOffice (Newer Libreoffice version start a 32-Bit process for 32-Bit TWAIN usage).
This Merge request also changes the twain_32.dll so that it send it's entry points earlier, before opening the data source. This is the same behaviour as the twaindsm.dll from the TWAIN organization from [https://github.com/twain/twain-dsm/%5D(https://github.com/twain/twain-dsm/bl...)
Otherwise sane.ds would in MSG_OPENDS try to find the DSM entry point based on the module-name "twain_32" in sane_main.c:60:
``` if (SANE_dsmentry == NULL) { HMODULE moddsm = GetModuleHandleW(L"twain_32");
if (moddsm) SANE_dsmentry = (void*)GetProcAddress(moddsm, "DSM_Entry");
if (!SANE_dsmentry) { ERR("can't find DSM entry point\n"); return TWRC_FAILURE; } } ```