Remove hardcoded colors to allow Custom/flavor/hc background colors

[jpnurmi]

I experimented with giving yaruUbuntuBudgieLight and yaruUbuntuBudgieDark the correct background colors; #f5f6f7 and #20222a, respectively. It works pretty well besides a few hardcoded fill colors here and there. 🎉 I don't know if this is a planned/supported use case but would be cool to support!

/cc @fossfreedom

[jpnurmi]

I didn't analyze what each value represents but some of these hardcoded color values could be problematic for those trying to customize the theme. Ideally, they would be either passed to createYaruLight/DarkTheme() or somehow calculated from the color scheme but I understand well that it might not always be possible or reasonable. :)

$ git grep --extended-regexp "\bColor(\.from\w+)?\("
lib/src/themes/common_themes.dart:const kDividerColorDark = Color.fromARGB(255, 65, 65, 65);
lib/src/themes/common_themes.dart:const kDividerColorLight = Color(0xffdcdcdc);
lib/src/themes/common_themes.dart:      light ? const Color(0xFFededed) : const Color.fromARGB(255, 40, 40, 40);
lib/src/themes/common_themes.dart:      ? const Color.fromARGB(255, 237, 237, 237)
lib/src/themes/common_themes.dart:      : const Color.fromARGB(255, 67, 67, 67);
lib/src/themes/common_themes.dart:    tertiary: const Color(0xFF18b6ec),
lib/src/themes/common_themes.dart:    tertiaryContainer: const Color(0xFF18b6ec),
lib/src/themes/common_themes.dart:    outline: const Color.fromARGB(255, 221, 221, 221),
lib/src/themes/common_themes.dart:    tertiary: const Color(0xFF18b6ec),
lib/src/themes/common_themes.dart:    tertiaryContainer: const Color(0xFF18b6ec),
lib/src/themes/common_themes.dart:    outline: const Color.fromARGB(255, 68, 68, 68),
lib/src/themes/common_themes.dart:      ? const Color.fromARGB(255, 34, 34, 34)
lib/src/themes/common_themes.dart:      ? const Color.fromARGB(255, 34, 34, 34)

[Feichtmeier]

yes, all colors then need to descend from the colorscheme inserted into the functions
most of those colors are just shades of grey so this won't be much of a problem. if you want to work on this just make sure that the resulting color you pick from colorscheme matches the old colors (by 95% or so, doesn't need to be 100% I guess)

[Feichtmeier]

Investigated a bit:

• scaling colors to background/surface colors is easy (thanks to @Jupi007 's nice scal() function)
• the problems are the YaruColor colors, we would need to parameterize the whole palette with arguments in createYaruLight/dark functions
• this is out of scope/too risky for 4.0.0, I would re-investigate after that