Made scanner arg const to getter functions.
Made a few more function arguments const's...
Scan view is responsible for opening/closing a scanner instance.
Lets not own a scanner reference and use the one in scan view.
Connect to signal handler when scan view changes active scanner.
Enable histogram module in scan view.
Added listener functionality to dt_scanner_t.
Added state handling of dt_scanner_t and callback to listeners.
Fixed formatting...
Added scan preview code stub...
Added initial scanner job preview scan...
Added scanner listener and handle state changes.
Added callback for preview which creates a scanner preview job.