revert deprecating Color withOpacity / opacity

[lukepighetti]

Read through the code and migration guide but still having trouble supporting the end result here.

Axioms

1. the vast majority of production codebases use .withOpacity(x), where x is 0.0–1.0 1
2. the internal implementation is now .withOpacity(x) => .withAlpha((255.0*x).round()); 2
3. the migration docs say to migrate .withOpacity(x) => .withValues(alpha: x); 3
4. .withValues(alpha: x) is more verbose and less obvious than .withOpacity(x) 4
5. designers communicate opacity as a percentage from 0%–100% not an integer from 0–255 5

Questions

1. why doesn't the internal implementation match the migration docs
2. why does withAlpha(x) take an int 0–255 and withValues(alpha: x) take a double 0–1.0
3. why does .withOpacity need to be deprecated at all

Recommendations

1. unify alpha to a double or an int across all color methods
2. undeprecate withOpacity method
3. undeprecate opacity getter

[lukepighetti]

Related issues:

• [packages] withOpacity is deprecated #159733
• Color deprecations should have a dart fix #160617
• Color.withValues(alpha: x) expects values between 0...1 instead of 0...255 #160592

[maxfrees]

why does .withOpacity need to be deprecated at all

[KRTirtho]

As a human being, I think perciving 0-1 is much easier than perciving 0-255. .withOpacity was an easier API and globally understood by all frontend/mobile/UI developers.
I'm guessing the change was made due to the confusion with Opacity widget's opacity. But, the method is in Color class so there's not much room for confusion

[mit-mit]

Please do not add +1 comments; it adds noise. Rather, please use the "thumps up" button on the top comment to indicate "+1". More details here.

[arnab]

Even if you don't revert it (I would prefer that too, for all the points already added), I would love to know why there is this discrepency:

why does withAlpha(x) take an int 0–255 and withValues(alpha: x) take a double 0–1.0

I see a lot of confusion in Flutter developers caused by this (like I have run into today). Alpha should either be 0..255, or 0..1, not "polymorphic" based on the context.

[bernaferrari]

I also think withValues is a bad name, it should have been copyWith to be consistent with the framework (and the day data classes become a reality).

[JediPixels]

I agree, it's anti-intuitive

[hamed-rezaee]

The absence of method overloading is really noticeable here. 😐

[jezell]

Color APIs really took a turn for the worse with the update. The lack of refinement with the API signatures has really overshadowed the P3 / HDR color support, which was an awesome addition.