Choosing a Handler

Documentation / Contents - File Handlers

Choosing a Handler

To set the handler for a type: select the type in the File Type list, then click a row in the Opens With list. Press Apply to write it.

How the Candidates Are Ranked

The Opens With list is not alphabetical and it is not arbitrary. Every type belongs to a handler class, and each class has a ranked ladder of applications, kept as a data table rather than compiled in, so the ranking can be tuned without rebuilding anything.

The ladder runs from the most native to the most generic: a Motif application first, then other toolkits, then a curses program, then a plain command-line tool. That is the order that keeps a Blueprint desktop looking like one.

Blueprint's own applications are looked for before anything on your command search path, so the desktop recommends its own File Manager for a directory rather than whatever else happens to be installed.

Rank decides the order in the list. Whether a program is installed decides whether it can be chosen at all; see the marks in The File Handlers Panel.

Auto-Pick Best

For every type that has no handler yet, take the highest-ranked application that is actually installed on this machine.

It does not overwrite a choice you have made. It fills the gaps, which is exactly what you want after installing a new application: press it and the types that program covers are filled in, and nothing you set by hand moves.

Press Apply afterwards to write the result.

Try It

The single most useful control here. It runs the selected type's chosen handler on a throwaway sample file of that type, so you can watch it work before you commit.

Use it whenever you have picked a handler you are not sure about. A command that looks right in a list and does nothing when run is the failure this button exists to catch.

If nothing installed here opens the selected type, Try It says so rather than running an empty command.

Opening Nothing

A type can be set to open nothing at all. Its handler is then the word NONE, and the effect is that the file shows its icon in the File Manager and never launches anything when opened.

That is the right setting for a kind of file you want recognised and labelled but never opened by accident: a database file, a lock file, a raw device image.

Placeholders

A type whose handler was never filled in carries a placeholder rather than a real command. The panel treats a placeholder as "no handler yet", which is why Auto-Pick Best fills it and why the Opens With list falls back to showing you the best candidate instead.