Better visual feedback for Autokey

Development Updates

1. As of v4.1, the autokey button is now red when enabled:
   #105574 - UI: Red Auto Keying Button - blender - Blender Projects
   

2. I just made an extension to border the viewport in red when autokey is enabled. It is pending review, but already downloadable here:
   Review: Autokey Highlight — Blender Extensions
   

Original Proposal

As Blender 2.8's UI is being worked, I think it's a good time for some visual feedback requests.

I think Blender really should have more visual feedback. Espacially for some "states" that you can enable by mistake, or forget to enable, or don't know if you enabled or not, .... Auto keyframe is one of them.

My idea is the following: When Autokey is enabled, some parts of the UI are overlayed in Red (I used HSV: 0%, 80%, 100%).

It doesn't have to be intrusive, but it has to communicate the info at least in the viewport and timeline I think.

Solutions Ideas

• Frame the active viewport (if you have several viewports, or quad view, maybe frame only the active one)
• Frame of ~2px wide, customizable, colored in RGBA red, customizable as well.
• Overlay only the active time range of the timeline, so it mimics the alternative time range's orange overlay without conflict. Color RGBA opaque red, customizable
• Customization is done in the user prefs (I thought about Overlay popover, but since it's not only on the viewport I thought it makes more sense in the user prefs.
• Should be toggleable (RGBA can still be set to fully transparent, but I guess it still computes something?)

How I went to this:

I've used several animations softwares (Blender, Maya, 3DS Max, Source FilmMaker, Akeytsu). My experience is:

• little texts in a corner are easy to miss. Ex. Blender's indicators about local/ortho/persp/playback, so many people completely miss them ;
• bigger text signs are well visible, but once you got the information they're just occupying a lot of space and just get annoying ;
• A big highlight on the autokey button works just fine, but only if you make it clear enough, big enough and always displayed. Maya does that, except you don't see it if you animate in a fullscreen viewport.
• Visual overlay on top of key editors for animations works the best. They are not in the way, but still noticeable enough. 3DS does that (+ noticeable autokey pushdown state):

There is a 2px wide frame on top of the active viewport (only the active one, if you have several viewports there's only one framed), and the frame slider background is all red.

I tried to make a guess of how this would work in Blender. Good to mention that the colors, opacity, frame size, could be customized or disabled in the user prefs (or in the overlay popover?)

(Also, bring back the autokey icon's red color . It really isn't the right icon without its red.)