applets/notifications: switch to horizontal timeout indicator
Reason for the change
The current circular timeout indicator is extremely fancy, but it suffers from two conceptually unresolvable challenges:
- By hugging the Breeze close icon, it looks bad with other icon themes whose close buttons have different shapes or dimensions. This also prevents us from ever changing the icon in Breeze.
- Putting a hardware-accelerated chart in every notification can increase resource usage on systems with less-powerful GPUs, especially when many notifications are shown at once.
To address these challenges, change the design to a very simple horizontal line below the header area.
This unblocks frameworks/breeze-icons!349.
Test plan
- Run with the patch for a while as notifications from NeoChat come in
- Run
while true; do notify-send foo bar; done
in a terminal window - Take a screenshot in Spectacle and see the screenshot
- Let the Spectacle notification time out and look at it in the history popup
Screenshots or screen recordings
Bugs fixed
No bugzilla tickets found, but it fixes the two above-mentioned conceptual issues with the current approach, and unblocks frameworks/breeze-icons!349.