- manually browse to a folder and XnViewMP will add any new files and will somehow identify changed files and decide if any need updating
- menu View->update catalog from files will recursively scan every file from a user-selected folder and unconditionally update DB with current file contents. Every file is scanned.
- From menu Tools->Settings the tab Browser->Catalog->Catalog has a button "Add Folder...". This allows user to select a folder, which is recursively scanned for files. The action seems to add info to catalog DB and it also builds thumbnails.
The problem is - I need to scan the entire photo library to allow xnview to catalog newly added folders and files.
The second option is no good as it unconditionally recans new and old images, which makes it far too slow.
Is the 3rd option the efficient way to do this? NO - it builds thumbnails for every file where it does not already have one cached.