More fine-grained rerender on variable updates?

[VixieTSQ]

Hi! I'm new to the project and have no understanding how it's internals work. But today I noticed as I was working on a notification daemon made for eww that works by setting a variable used as a literal every time a notification is added or removed, that the window flickers every update. My WM also takes a very short amount of time to reapply the blur I am applying to the window. My guess as to why this is happening is that every update to this variable is causing eww to destroy every widget in the window, then create them all again, even though theoretically it could just delete or create the one widget that has actually changed.

Is my guess correct?

[VixieTSQ]

A relatively simple solution would be the introduction of a new widget property named key, allowing for a similar approach to how Svelte handles keyed each blocks. It would maybe look something like this

(box
    (notification :key "1")
    (notification :key "2")
    (notification :key "3")
    (notification :key "4"))

Say all these notifications come from a (literal :content notifs). When notifs gets updated, eww can see exactly which widget got removed and which got added. And so eww can rerender only what has actually changed. This also allows for a system for FLIP animations, which would be an extremely cool feature.

[VixieTSQ]

It looks like you don't even have to be using the variable as a literal. I'm using and setting a variable for the value of a scale bar, and the entire window updates and flickers every time I update the variable.

[VixieTSQ]

Ah! I think I found the problem with both of these examples. Spurious calls to eww open foobar causes the window to reload. Although I still think having FLIP animations would be great, I have my issue solved.