The opacity change on a slide transition is barely visible

[mpost]

Describe the problem

The opacity is multiplied by 20 which pushes it over 1 nearly instantly.

See

svelte/packages/svelte/src/runtime/transition/index.js

Line 108 in effeb7a

`opacity: ${Math.min(t * 20, 1) * opacity};` +

Describe the proposed solution

Control the opacity scaling factor. Alternatively remove the factor altogether, making it behave the same as the fade transition.

Alternatives considered

You can create your own transition combining the slide transition and a manual change of opacity.

Importance

would make my life easier

[Rich-Harris]

This is deliberate — it's a slide transition, not a fade transition. Subjectively, it looks better if there's a consistent 'metaphor' when adding and removing elements. The only reason we change opacity at all is so there isn't a sharp discontinuity at the very start of the transition.

I say subjectively because this is of course a matter of opinion, but the transition API exists so that you're not bound by the built-in decisions.