Open or Edit a QML file?

One limitation of doing things based purely on the MIME type of a file is that sometimes things that might be sniffed as C source code are really not. This also comes up with XML files. One solution which feels like adding a level of indirection is having the sniffer say this is XML and what the schema is, or this looks like C source but is really a QML interface. While this blog post presents a libferris oriented solution, I thought I'd syndicate because the core problem is broadly applicable.

Because I tend to want to have the computer do different things for the same mime type depending on where it is located or other metadata, libferris lets you tell it what to do based on any arbitrary predicate, instead of a mimetype == value test.

Like most things, this is setup and edited using... drum roll... a filesystem. The filtered bindings are evaluated before the normal mimetype value tests, and if a filtered binding is found it is used instead of any "generic" mimetype based action.

So, for the Qt SDK, I can have double click run the QML application and middle click open the source in emacs with a setup like the one below. Notice that I restrict the override to only /usr/local/qt URLs so I don't go handing QML files from arbitrary sources to qmlviewer. For those new to libferris the "| ferris-redirect" is like the shell ">" but can operate on any virtual filesystem object directly, without using FUSE etc.

fmkdir mime://filtered-bindings/qt-qml
fmkdir mime://filtered-bindings/qt-qml/actions
echo '(&(url=~file:/*usr/local/qt.*)(name-extension==qml))' \
  | ferris-redirect mime://filtered-bindings/qt-qml/ffilter

ftouch  mime://filtered-bindings/qt-qml/actions/open
echo -n misc/qmlviewer \
 | ferris-redirect -a ferris-appname mime://filtered-bindings/qt-qml/actions/open

ftouch  mime://filtered-bindings/qt-qml/actions/edit
echo -n emacs \
 | ferris-redirect -a ferris-appname mime://filtered-bindings/qt-qml/actions/edit

These actions are used in the ego file manager as well as from the command line with
$ ferris-file-action -v foourl.qml
to view. Of course, alias fv="ferris-file-action -v" is your friend.