The selection of the FileHandler to use to open a file of a specific type is normally done automatically based on the Configuration.
This automatic selection applies when opening files through any of the following means:
As command line parameter open upon application start.
Dropping a file somewhere onto the applications desktop.
Double clicking on a file in the directory browser window.
Sometimes this default selection is not what is desired. Hence the directory browser window supports manual selection of the FileHandler to open a file by right clicking onto it and choosing it from the appearing popup menu. This menu lists all those FileHandlers which are configured to (or consider themselves capable of) support the detected MIME type of the file. If there are several FileHandlers which support the same operation (e.g. “Edit”) on that MIME type, the first one will be listed on top level of the popup menu, while the others will be listed by their names in a submenu; otherwise only the operation appears in the menu on top level (the FileHandler behind that operation will be shown in the tooltip of that menu item).
If this catalog of possibilities still doesn't list the desired FileHandler, the user can press the SHIFT key when right clicking to open the popup menu. This will show an additional entry in the submenu, allowing to manually select any of the available FileHandlers to open the file at hand. Not all FileHandlers support all kinds of files, however, so this approach might easily lead to an error message, stating that the file cannot be opened by the selected handler.
The same mechanism for the selection of the FileHandler to use is available when dropping files on the desktop area or the desktop windows title bar. It requires to press the CTRL key when dropping the files. The selection dialog will then appear for every file to be opened.
In case no plugins have yet been configured, the selection process will fall back on the single embedded FileHandler that is always guaranteed to be available, regardless of the configuration. This handler will just be capable of displaying the file system information of the selected file, along with the MIME type that was detected according to the configuration. It is the same information that is displayed by the directory browser window in its right lower pane. This ensures the application is always fully functional for the purposes it can handle all by itself (e.g. the file handling operations).