Tag editor interface improvements

[autogris]

Current interface for editing tags for multiple files is inefficient when trying to edit as fast as possible a large collection in library. For instance, trying to mass change "Year" of files in a given album or selection, gives me a default window which requires me to uncheck every single "Apply current value to all tracks" except that related to "Year" (which then is automatically unchecked as soon as I fill the field, forcing me to recheck it), and those buttons are dispersed throughout the screen making it easy to miss one and accidentally overwrite a tag which I didn't intended to make common to all files. Not only it lacks a button for mass deselect, but the buttons are not very clear in their description/symbol of what they function exactly is, specially the "backspace"/"arrow with a cross", which doesn't have even a tooltip and I still am not sure what is its function.

Steps to Reproduce (for bugs)

1. Select several files from an album or any other category
2. Click Track Properties
3. All the several spread buttons of "Apply current value to all tracks" are randomly selected
4. Buttons are confusing about their purpose

Expected Behavior

• Those button should all be unselected by default.
• There should at least exist a "Select All" and a "Unselect all" button.
• Adding a tooltip to the mysterious "Backspace"/"Arrow with X" button and a more explicit and clear icon to represent what buttons do.
• Ideally a better placement for this function activation so one could easily track all that are selected.

Environment

• Operating System and version: Linux kernel 5.10.19

• Exaile Version: 4.1.0
  GStreamer: 1.18.3
  GTK+: 3.24.26
  GTK+ theme: Breeze-Dark
  Locale: pt_BR UTF-8
  Mutagen: 1.45.1
  PyGObject: 3.38.0
  Python: 3.9.2

[sjohannes]

I've added a tooltip to the Clear buttons in 6343c7b .

The "apply to all" toggle button is pre-toggled if the value of a particular tag is the same between all the edited tracks. I think it makes sense to change this behaviour when the value is empty.

[luzip665]

Hi,

I got a similar problem of understanding how the button works on the current master.

Steps to Reproduce

1. Open several tracks with same artist
2. Open Track Properties
3. The button "Apply to all tracks" is active for artist
4. Change the artist
5. The button "Apply to all tracks" becomes inactive
6. Click on Apply or switch to the next track, the value is applied to all tracks although the button is inactive

May be it is an idea to use the button "Apply current value to all tracks" as an action button instead of a toggle button.
So if I click on it, the value is applied to all tracks.
Because actually it seems to be a reversible action, but it is not.

[luzip665]

May relate to #752

I would really like to change the type and the behaviour of the button.
Are there any objections?