Move all color constants to a single module

[sunjay]

In #171, I suggested that we move the color constants from the color module into the Color struct itself. After merging #186, I spent some time thinking about it a bit more and wondered if we might want to take a different approach.

Here are some problems with how we currently define color constants and how we show them in the documentation:

• Color constants are rarely used but take up a lot of space in the documentation for Color. Most people use the color name strings instead (e.g. "cherry red") because they are more convenient and more prominently used throughout the docs. The constants make it so you have to scroll pretty far to see the rest of the documentation for Color.
• The COLORS and COLOR_NAMES static variables don't actually contain all of the colors in the crate. We split the colors between two places so those constants only contain the colors that are defined nearby.

To solve all of this, I am now suggesting that we move all of the color constants to a single color_consts module. This will allow us to make a single, complete list of all the supported color names and avoid filling the Color struct documentation with information that is rarely used.

To-do

• [x] create a new file src/color/color_consts.rs

• [x] move the contents of the extra_colors module to that file

• [x] move the documentation for extra_colors to that file (don't forget to replace /// with //!)

• [x] move the color constants currently defined on Color into that file (there should no longer be any color constants in Color)

• [x] change the macro that defines COLORS and COLOR_NAMES to define those constants within an impl Color block (this should create a single set of those constants that actually contains ALL the colors supported in this crate)

• [x] stop re-exporting extra_colors and re-export color_consts instead

• [x] fix compiler resulting errors

• [x] update the documentation

• [x] see the To-do list in #171 for more ideas of what you might need to do

• [x] optional: reference color_consts at the bottom of the Color struct documentation
  

  The color_consts module contains a full list of all the supported color names.

• [ ] optional: reference color_consts in the documentation of methods that take Into<Color>

Please don't hesitate to ask questions in the comments below or on Zulip!

cc @noeddl in case you're interested in doing a follow up from #186.

[noeddl]

@sunjay Yes, I would like to continue working on this.

[noeddl]

I have a question about this to-do:

change the macro that defines COLORS and COLOR_NAMES to define those constants within an impl Color block (this should create a single set of those constants that actually contains ALL the colors supported in this crate)

As we already noticed in the previous PR, defining these variables within an impl Color block won't work because static variables are not allowed as associated items in structs. So we should maybe continue using the functions that you came up with instead?

[sunjay]

As we already noticed in the previous PR, defining these variables within an impl Color block won't work because static variables are not allowed as associated items in structs. So we should maybe continue using the functions that you came up with instead?

Oops! You are totally right. Yes, please use the associated functions instead. Thanks!