Indicate that tab will be closed soon

When tab is about to close it's favicon should be changed.

Alternatively, the title text could grey out. AutoClose Tabs did this.

Sounds like a good idea, but it's not future proof. It can be achieved only with API which will be deprecated soon.

Having a counter updating in the title? But that feels way too retro (even aesthetic)

Seeing other plugins, a common way to display status is the favicon: TabMixPlus attaches little icons to the icon of the webpage, TileTab uses colored borders. Also I believe animated icons (gif?) can be displayed.

Yep, I am thinking about something like this. It could be tricky to achieve but it will be looking nice and should be future proof.

once we got this ... make actual closing optional... I would be ok closing tabs myself an indication I did not use one for a while would be great help.

@mafjmafj that should be a separate issue.

Not sure, can add-ons use a canvas while not being in the foreground? There are functions to draw a given image onto a canvas, and also functions to get the full content of the canvas as data: url.