Scan

When pressing "scan" button:

1. The scanner will first read all files informations (recursively for sources dirs), read archive if any (entries, crc, ...) from all sources and destinations directories, including implicit directories (backup for example), and store in disk cache files (for next scan)
2. Then it will compare the destination with declared machines/roms/disks in current loaded profile, to find fixes and add missing roms/disks available from sources or even somewhere else in the destination (especially when switching from merged to split mode)

All these operations are shown via this progress bar

"Report" button will show what is fixable, partially fixable, not available, and good

Nothing will be fixed, without pressing "Fix". If there is no fixes available, because no fixes are needed or because it's not possible to fixes with provided sources, the "Fix" button will be kept disabled, otherwise it will be enabled