options: Add truecolor to control the usage (#2867)

- `auto`: enable usage of true color if it is supported, otherwise disable it
- `on`: force usage of true color
- `off`: disable true color usage

Co-authored-by: Dmytro Maluka <dmitrymaluka@gmail.com>

README.md

@@ -47,7 +47,7 @@ You can also check out the website for Micro at https://micro-editor.github.io.
 - Syntax highlighting for over [130 languages](runtime/syntax).
 - Color scheme support.
   - By default, micro comes with 16, 256, and true color themes.
-- True color support (set the `MICRO_TRUECOLOR` environment variable to 1 to enable it).
+- True color support.
 - Copy and paste with the system clipboard.
 - Small and simple.
 - Easily configurable.

internal/config/settings.go

@@ -36,6 +36,7 @@ var optionValidators = map[string]optionValidator{
 	"scrollmargin":    validateNonNegativeValue,
 	"scrollspeed":     validateNonNegativeValue,
 	"tabsize":         validatePositiveValue,
+	"truecolor":       validateChoice,
 }
 
 // a list of settings with pre-defined choices
@@ -46,6 +47,7 @@ var OptionChoices = map[string][]string{
 	"matchbracestyle": {"underline", "highlight"},
 	"multiopen":       {"tab", "hsplit", "vsplit"},
 	"reload":          {"prompt", "auto", "disabled"},
+	"truecolor":       {"auto", "on", "off"},
 }
 
 // a list of settings that can be globally and locally modified and their
@@ -99,6 +101,7 @@ var defaultCommonSettings = map[string]interface{}{
 	"tabmovement":     false,
 	"tabsize":         float64(4),
 	"tabstospaces":    false,
+	"truecolor":       "auto",
 	"useprimary":      true,
 	"wordwrap":        false,
 }

internal/screen/screen.go

@@ -184,10 +184,13 @@ func Init() error {
 	drawChan = make(chan bool, 8)
 
 	// Should we enable true color?
-	truecolor := os.Getenv("MICRO_TRUECOLOR") == "1"
-
-	if !truecolor {
+	truecolor := config.GetGlobalOption("truecolor").(string)
+	if truecolor == "on" || (truecolor == "auto" && os.Getenv("MICRO_TRUECOLOR") == "1") {
+		os.Setenv("TCELL_TRUECOLOR", "enable")
+	} else if truecolor == "off" {
 		os.Setenv("TCELL_TRUECOLOR", "disable")
+	} else {
+		// For "auto", tcell already autodetects truecolor by default
 	}
 
 	var oldTerm string

runtime/help/colors.md

@@ -47,10 +47,7 @@ color support comes in three flavors.
   displaying any colorscheme, but it should be noted that the user-configured
   16-color palette is ignored when using true-color mode (this means the
   colors while using the terminal emulator will be slightly off). Not all
-  terminals support true color but at this point most do. True color
-  support in micro is off by default but can be enabled by setting the
-  environment variable `MICRO_TRUECOLOR` to 1.  In addition your terminal
-  must support it (usually indicated by setting `$COLORTERM` to `truecolor`).
+  terminals support true color but at this point most do (see below).
   True-color colorschemes in micro typically end with `-tc`, such as
   `solarized-tc`, `atom-dark`, `material-tc`, etc... If true color is not
   enabled but a true color colorscheme is used, micro will do its best to
@@ -84,11 +81,12 @@ These may vary widely based on the 16 colors selected for your terminal.
 
 ### True color
 
-True color requires your terminal to support it. This means that the
-environment variable `COLORTERM` should have the value `truecolor`, `24bit`,
-or `24-bit`. In addition, to enable true color in micro, the environment
-variable `MICRO_TRUECOLOR` must be set to 1. Note that you have to create
-and set this variable yourself.
+Micro enables true color support by default as long as it detects that the
+terminal supports it (which is usually indicated by the environment variable
+`COLORTERM` being set to `truecolor`, `24bit` or `24-bit`). You can also force
+enabling it unconditionally by setting the option `truecolor` to `on` (or
+alternatively by setting the environment variable `MICRO_TRUECOLOR` to 1, which
+is supported for backward compatibility).
 
 * `solarized-tc`: this is the solarized colorscheme for true color.
 * `atom-dark`: this colorscheme is based off of Atom's "dark" colorscheme.

runtime/help/options.md

@@ -462,6 +462,19 @@ Here are the available options:
 
     default value: `false`
 
+* `truecolor`: controls whether micro will use true colors (24-bit colors) when
+   using a colorscheme with true colors, such as `solarized-tc` or `atom-dark`.
+   * `auto`: enable usage of true color if micro detects that it is supported by
+      the terminal, otherwise disable it.
+   * `on`: force usage of true color even if micro does not detect its support
+      by the terminal (of course this is not guaranteed to work well unless the
+      terminal actually supports true color).
+   * `off`: disable true color usage.
+
+   Note: The change will take effect after the next start of `micro`.
+
+   default value: `auto`
+
 * `useprimary` (only useful on unix): defines whether or not micro will use the
    primary clipboard to copy selections in the background. This does not affect
    the normal clipboard using `Ctrl-c` and `Ctrl-v`.