Introduce tone-based surfaces and accent color add-ons - Part 2

[QuncCccccc]

Fixes #115912

This PR is to introduce 19 new color roles and deprecate 3 color roles in ColorScheme.
Tone-based surface colors (7 colors):

• surfaceBright
• surfaceDim
• surfaceContainer
• surfaceContainerLowest
• surfaceContainerLow
• surfaceContainerHigh
• surfaceContainerHighest

Accent color add-ons (12 colors):

• primary/secondary/tertiary-Fixed
• primary/secondary/tertiary-FixedDim
• onPrimary/onSecondary/onTertiary-Fixed
• onPrimary/onSecondary/onTertiary-FixedVariant

Deprecated colors:

• background -> replaced with surface
• onBackground -> replaced with onSurface
• surfaceVariant -> replaced with surfaceContainerHighest

Please checkout this design doc for more information:)

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie or stuartmorgan on the #hackers channel in Chat (don't just cc them here, they won't see it! Use Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[HansMuller]

I haven't read all the changes yet; just a few comments from yesterday.

[HansMuller]

I assume that we're not deprecating this now because there's no substitute? If the Material library is no longer using this color, we should document that here and in the ColorScheme class doc. We need to explain why it's not longer being used - which will require a bit of an explanation.

[QuncCccccc]

Even though surfaceTint is no longer used by any widgets, the token database still keep this color in the color scheme(carbon), so I didn't mark this as deprecated. Will add more explanation! Thanks a lot for taking time to review this big PR!

[HansMuller]

This looks great. Just some small-time feedback about ColorScheme doc strings.

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[github-worst-company]

Why do many of the colours use the fallback instead of implementing the colour? Having just the tokens and then adding it yourself doesn't make much sense when using the dynamic colour generator.

[QuncCccccc]

Why do many of the colours use the fallback instead of implementing the colour? Having just the tokens and then adding it yourself doesn't make much sense when using the dynamic colour generator.

Hi! We've updated ColorScheme.fromSeed and fromImageProvider methods so they can build ColorSchemes where each color role will have their values from MaterialDynamicColors, instead of fallbacks.

[github-worst-company]

Wow that's great, thanks a lot!

[knott-todd]

Hey, I see this was merged to master. I'd really like to use it in my app, are there any plans to merge to beta? Flutter docs recommended against connecting to the master channel...

[guidezpl]

Betas are created monthly, so expect this change in the next beta release. Please see https://github.com/flutter/flutter/wiki/Where's-my-commit%3F#finding-the-versions-that-contain-framework-commit-x for more.