Mouse Operations

In every view

Wheel	Scroll vertically
`Ctrl` + Wheel	Scroll vertically by a whole screen per notch (fast)
Right button + drag	Scroll vertically (grab the listing and move it)
Right double-click	Back to the previous selection (same as `Esc`)
Drag the center separator	Resize the two panes; double-click centers it
Drop files from the Explorer	Drop two files or folders at once to compare them; drop a single one onto a pane to replace that side and keep the other. A dropped `.lic` file installs a license instead

File comparison

Left button (click or drag)	Mark lines on one or both sides — the marked area is what Copy, Paste and Delete operate on
Drag the marked area across the separator	Copy those lines onto the corresponding area of the other side — see Merging Changes. The source side stays unchanged; the receiving side has to be writable

Directory comparison

Double-click a row	Open that file pair for comparison; entries inside an archive are extracted to a temporary file first
Click a column title	Sort by that column (on the clicked side); a second click on the same title reverses the direction — see Directory Sorting
Double-click a column separator	Fit the column left of it to its content
Right-click a row	Windows Explorer context menu for that file, folder or archive (release the button without moving the mouse — moving it scrolls instead)
Right-click the empty area	A small view menu with the most common display commands

Deleting Thumbs.db on a network share may fail with “the file is in use in Diffoniq”. That is Windows, not Diffoniq: the shell’s context menu runs inside the application, and when its delete confirmation renders the item’s icon, the Windows thumbnail cache opens the folder’s Thumbs.db as a thumbnail store and keeps it open — so the delete that follows finds the file locked by the very process it runs in. Explorer shows the same behaviour on network folders. The cure is the Windows policy “Turn off the caching of thumbnails in hidden thumbs.db files” (User Configuration › Administrative Templates › Windows Components › File Explorer; registry HKCU\Software\Policies\Microsoft\Windows\Explorer\DisableThumbsDBOnNetworkFolders = 1), after which the file deletes normally.