options: Add truecolor to control the mode

- `auto`: leaves the detection to `tcell`
- `on`: forced usage, same as `$MICRO_TRUECOLOR` set to 1
- `off`: default, can be overriden by `$MICRO_TRUECOLOR`

README.md

@@ -63,7 +63,10 @@ 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
+  - set the option `truecolor` to `auto` or `on` ..
+  - set the `MICRO_TRUECOLOR` environment variable to 1 to enable it
+  - both ways do only work in case the terminal supports true color mode
 - Copy and paste with the system clipboard.
 - Small and simple.
 - Easily configurable.

internal/config/settings.go

@@ -35,6 +35,7 @@ var optionValidators = map[string]optionValidator{
 	"scrollmargin":    validateNonNegativeValue,
 	"scrollspeed":     validateNonNegativeValue,
 	"tabsize":         validatePositiveValue,
+	"truecolor":       validateChoice,
 }
 
 // a list of settings with pre-defined choices
@@ -44,6 +45,7 @@ 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
@@ -95,6 +97,7 @@ var defaultCommonSettings = map[string]interface{}{
 	"tabmovement":     false,
 	"tabsize":         float64(4),
 	"tabstospaces":    false,
+	"truecolor":       "off",
 	"useprimary":      true,
 	"wordwrap":        false,
 }

internal/screen/screen.go

@@ -150,9 +150,16 @@ func Init() error {
 	drawChan = make(chan bool, 8)
 
 	// Should we enable true color?
-	truecolor := os.Getenv("MICRO_TRUECOLOR") == "1"
+	truecolor := (config.GetGlobalOption("truecolor").(string) == "auto") ||
+		(config.GetGlobalOption("truecolor").(string) == "on") ||
+		(os.Getenv("MICRO_TRUECOLOR") == "1")
 
-	if !truecolor {
+	if truecolor {
+		if (config.GetGlobalOption("truecolor").(string) == "on") ||
+			(os.Getenv("MICRO_TRUECOLOR") == "1") {
+			os.Setenv("COLORTERM", "truecolor")
+		}
+	} else {
 		os.Setenv("TCELL_TRUECOLOR", "disable")
 	}
 

runtime/help/colors.md

@@ -49,8 +49,12 @@ color support comes in three flavors.
   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 `$COLORTERM` to `truecolor`).
+  the option `truecolor` to `on` or the environment variable `MICRO_TRUECOLOR`
+  to 1 to force the usage of true color mode.
+  In addition your terminal must support it (usually indicated by setting
+  `COLORTERM` to `truecolor`).
+  Furthermore it can be enabled by setting the option `truecolor` to `auto` then
+  the availability will be determined by `$COLORTERM`.
   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
@@ -86,9 +90,10 @@ These may vary widely based on the 16 colors selected for your terminal.
 
 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.
+or `24-bit`. In case the currently used terminal doesn't "support" true color
+within the mentioned `COLORTERM` then the usage can be forced by setting the
+option `truecolor` to `on` or the environment variable `MICRO_TRUECOLOR` to 1.
+Note that you have to create and set this environment variable yourself.
 
 * `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

@@ -442,6 +442,19 @@ Here are the available options:
 
 	default value: `false`
 
+* `truecolor`: controls the usage of the true color support/mode.
+	* `auto`: Leaves the true color support detection to `tcell`, which evaluates
+	   the `$COLORTERM` environment variable. This option can be overriden by
+	   setting `$MICRO_TRUECOLOR` to `1` too.
+	* `on`: Will force the usage of true color, but will need terminal support
+		to work properly. This option will override `$MICRO_TRUECOLOR` set to `0`.
+	* `off`: true color support disabled, but can be overriden with the
+		`$MICRO_TRUECOLOR` environment variable set to `1`.
+
+	Note: The change will take effect after the next start of `micro`.
+
+	default value: `off`
+
 * `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.