Provide option to change behavior of middle click

This is an enhancement request. Currently, middle clicking on the panel icon for the plugin toggles mute on and off. I would like to have an option to change this behavior to perform other actions. In particular, I would prefer it to switch between output devices, although I expect some other options would be useful in other situations.

What I don't like about this type of output cycling is that the user gets no feedback about the output that is currently selected (unless you show a notification) nor of the order in which outputs are cycled.

The panel icon has a tooltip that shows the volume, and this immediately updates to the volume of the new output if the tooltip is already visible when the output is changed. Perhaps this could also show the selected output, always or only when it has been changed via middle click?

mentioned in merge request !12

Alternative idea: use ctrl/shift + mouse wheel to switch output/input devices. User feedback can be provided by updating the button's tooltip, IIRC it shows the new text immediately.

Is eliminating the need for a config property a motivating factor in this alternative? That appeals to me, but I am not yet familiar with the design philosophies in play around here.

Yes, avoiding a new preference is a big motivation.

I've been using !13 since yesterday, switching perhaps a dozen times. It feels much less comfortable and convenient than being able to middle click. That said, I'm happy to get that MR into shape if it's desired.

Well, if you have more ideas please share them, otherwise a preference to change the behavior of middle click is a no-go for me, @ochosi may disagree and has the final say.

mentioned in merge request !13

@sparr I'm wondering if 'cycling between output sources' is really what you ever want to do. I mean unless you know the order of your output devices this is just going to be guess-work. Wouldn't it be better to bind specific output sources to keyboard shortcuts and use pactl and notify-send (if you want a visible notification of the change) in a bash script?

In many use cases, it is much easier for me to use the mouse than the keyboard, especially an esoteric key combination.

If I understand correctly, you want to blindly switch audio input/output devices by middle click on icon (same what you can do from trays menu)?