Crate concolor

Control console coloring across all dependencies

Motivation

Detecting a terminal’s color capabilities and passing it down to each writer can be obnoxious. Some crates try to make this easier by detecting the environment for you and making their own choice to print colors. As an application author, you own the experience for your application and want the behavior to be consistent. To get this, you have to dig into each crate’s implementation to see how they auto-detect color capabilities and, if they don’t do it how you want, hope they provide a way to override it so you can implement it yourself.

Like with logging, your terminal’s capabilities and how to treat it is a behavior that cuts across your application. So to make things more consistent and easier to control, concolor introduces shared detection logic that all crates can call into to get consistent behavior. The application author can then choose what feature flags are enabled to decide on what the end-user experience should be.

[[bin]]s

[dependencies]
concolor = { version = "0.0.9", features = "color" }

Notes:

• With the 2021 edition / resolver = "2", you will also need to specify this in your build-dependencies if you want build.rs to have color as well.

If you are providing a command line option for controlling color, just call

let when = concolor::ColorChoice::Always;
concolor::set(when);

See also concolor-clap

[lib]s

The [[bin]] is responsible for defining the policy of how colors are determined, so to depend on concolor:

[dependencies]
concolor = { version = "0.0.9", default-features = false }

At times, you might want to provide a convenience feature for color support, so you could also:

[features]
default = ["color"]
color = "concolor/auto"

[dependencies]
concolor = { version = "0.0.9", optional = True}

Notes:

• Your choice on whether to make this default or not
• Depending on your context, name it either color (for a crate like clap) or auto (for a crate like termcolor)

Then just ask as needed:

let stdout_support = concolor::get(concolor::Stream::Stdout);
if stdout_support.ansi_color() {
    // Output ANSI escape sequences
    if stdout_support.truecolor() {
        // Get even fancier with the colors
    }
} else if stdout_support.color() {
    // Legacy Windows version, control the console as needed
} else {
    // No coloring
}

Features

• auto: Guess color status based on all possible sources, including:
  • api_unstable: Allow controlling color via the API (until 1.0, this is not guaranteed to work across crates which is why this is _unstable)
  • interactive: Check if stdout/stderr is a TTY
  • clicolor: Respect CLICOLOR spec
  • no_color: Respect NO_COLOR spec
  • term: Check TERM
  • windows: Check if we can enable ANSI support

Structs

Color

Current color state for a Stream

Enums

ColorChoice

Selection for overriding color output with set

Stream

Output stream to get() the Color state for

Functions

get

Get the current Color state for a given Stream

set

Override the detected ColorChoice