Thunar (Xfce’s file manager) has a rather unintuitive behaviour to select the default app: For some file types it seems that chossing a program of the context menu’s “Open With…” overwrites the default application for that file type… That means, once I open a PNG file with Gimp, Gimp becomes the default for PNGs and double clicking the next PNG will result in a >300 ms delay to launch Gimp. Strangely, that only happens for some file types. Others seem to be invariant to the open-with-selection…? Anyway, bugged me enough to finally look into it..

It seems, that this was a design decision whithin the Xfce project: If you actively selected a default application it will stay the default application, even if you temporarily open-with another application. If you did not actively select a default application, the last application will be used by default -> this is my annoying use case.

At least, I now know what is needed to do: Actively select a default applications…

You can do it using the UI by right-clicking a file of the type and selecting Open With Other Application…. Then select the desired application and make sure you tick Use as default for this kind of file. From then on, this will be your default application, until you actively change it.

That may be a good solution for many of you, but it’s also pretty tedious to find and right-click all the different file types. And of course it’s not the way I’m working. There must be a nicer option - and there is! The configuration for Thunar’s mime type bindings is stored in ~/.config/mimeapps.list :)

This file contains two sections:

• [Added Associations] contains a list of known file types and possible associations to applications
• [Default Applications] is a list of file types and … their default application…

Thus, to add another default-application-association, you just need to append another line to the [Default Applications] section. You may just copy a line from the [Added Associations] and reduce the number of applications to one, eg. for PNG images:

If your desired application is not yet int the list of Added Associations, you may find it in /usr/share/applications/. If you still cannot find an application, you can generate a new one. Just create a file ~/.local/share/applications/YOURAPP.desktop containing something like this:

Afterwards, you can use YOURAPP.desktop in ~/.config/mimeapps.list.

Looks like I’m often in trouble with default applications…? Is it just me?
If you have problems with KDE applications, you may want to look into my article on KDE file type actions