Very good. Thank you for opening this topic. From a user perspective; I'll answer something basic and minimal: a yellow icon (maybe with a orange outline) appears on the bottom (near the memory usage) around 80% of max resources used. The icon might look like a button one can press: a pop-up display a small text explaining basic things about ram and proposing solution: reduce layer stack by merging, split large animation into scenes, etc...

I'm thinking we should have an icon that shows up at 50%, as the current one shows up at 87.5%. Furthermore, I remember an old presentation of this shooter game where they set the healthbar to start warning the player at 50%, because humans aren't very good at judging their resources, and they found players would manage their resource(health) much better when they were warned at 50%.

Another option would be to change the label that shows the current image dimensions / size into a bar, much like the plasma memory reporting widget, and have that go from bright green to dark red to indicate that the memory usage is getting really high.

Secondly, I'm wondering whether Krita might be able to give an indicator in the timeline for when the ram usage might be too high? Like, a 'soft' recommended limit on frames, where artists can still make more frames, but it becomes increasingly less recommended. Like, for example, if we'd assume each frame has unique data on it, how many frames could be possible given the currently available ram? @scottpetrovic, @dkazakov, @jounip do you think this is a possible idea?

Regarding the bar, I was thinking something like this(though perhaps should go into red faster). The smaller lighter box at the start is the imagesize compared to the full colored box, which would be the total ram consumption(stats.totalMemorySize) vs total memory limit. Problem: Sometimes the imagesize(stats.imageSize) is larger than the total ram consumption(stats.totalMemorySize), and I don't know why, @dkazakov?

I checked with colorblindness simulation filters, the red and yellow are still very distinguishable, but we might none the less think of something shape based to make it less ambiguous? (EDIT: maybe smilies?) The blue in this case is the theme's highlight color.

Anyway, this will require a new widget, especially if we want to ensure it'll still keep the pop-up button functionality.

I like the colored bar, but I do think that having an icon with danger sign would also helpful.

ok, for the frames stuff, based on this reddit post:
https://www.reddit.com/r/krita/comments/arr8rw/memory_limit_reached_i_cant_save_my_frames/

User has a large animation, and Krita has too little memory to clone and render. We should perhaps prevent the user from making more frames than they can render(or warn them). (Loading more frames than they can render is fine, but not making them) This is also why I am hoping for a soft-limit/warning when we reach such a threshold.