Add ambiguouswidth option

internal/action/command.go

@@ -601,6 +601,8 @@ func doSetGlobalOptionNative(option string, nativeValue any) error {
 		} else {
 			config.SetAutoTime(0)
 		}
+	} else if option == "ambiguouswidth" {
+		util.SetAmbiguousWidth(nativeValue.(string))
 	} else if option == "paste" {
 		screen.Screen.SetPaste(nativeValue.(bool))
 	} else if option == "clipboard" {

internal/config/settings.go

@@ -21,6 +21,7 @@ type optionValidator func(string, any) error
 
 // a list of settings that need option validators
 var optionValidators = map[string]optionValidator{
+	"ambiguouswidth":  validateChoice,
 	"autosave":        validateNonNegativeValue,
 	"clipboard":       validateChoice,
 	"colorcolumn":     validateNonNegativeValue,
@@ -41,6 +42,7 @@ var optionValidators = map[string]optionValidator{
 
 // a list of settings with pre-defined choices
 var OptionChoices = map[string][]string{
+	"ambiguouswidth":  {"auto", "single", "double"},
 	"clipboard":       {"internal", "external", "terminal"},
 	"fileformat":      {"unix", "dos"},
 	"helpsplit":       {"hsplit", "vsplit"},
@@ -110,6 +112,7 @@ var defaultCommonSettings = map[string]any{
 // a list of settings that should only be globally modified and their
 // default values
 var DefaultGlobalOnlySettings = map[string]any{
+	"ambiguouswidth": "auto",
 	"autosave":       float64(0),
 	"clipboard":      "external",
 	"colorscheme":    "default",

internal/screen/screen.go

@@ -7,6 +7,7 @@ import (
 	"sync"
 
 	"github.com/micro-editor/micro/v2/internal/config"
+	"github.com/micro-editor/micro/v2/internal/util"
 	"github.com/micro-editor/tcell/v2"
 )
 
@@ -182,6 +183,8 @@ func TempStart(screenWasNil bool) {
 func Init() error {
 	drawChan = make(chan bool, 8)
 
+	util.SetAmbiguousWidth(config.GetGlobalOption("ambiguouswidth").(string))
+
 	// Should we enable true color?
 	truecolor := config.GetGlobalOption("truecolor").(string)
 	if truecolor == "on" || (truecolor == "auto" && os.Getenv("MICRO_TRUECOLOR") == "1") {

internal/util/util.go

@@ -91,6 +91,31 @@ func init() {
 	}
 
 	Stdout = new(bytes.Buffer)
+
+	envAmbiguousWide = runewidth.EastAsianWidth
+}
+
+// envAmbiguousWide is the ambiguous width detected from the environment
+// (the locale environment variables and RUNEWIDTH_EASTASIAN) at startup
+var envAmbiguousWide bool
+
+// SetAmbiguousWidth sets how wide the characters with the East Asian
+// Ambiguous width property (see Unicode Standard Annex #11) are considered
+// to be: one column ("single"), two columns ("double") or as many columns
+// as the environment implies ("auto")
+func SetAmbiguousWidth(mode string) {
+	var wide bool
+	switch mode {
+	case "single":
+		wide = false
+	case "double":
+		wide = true
+	default:
+		wide = envAmbiguousWide
+	}
+	// go-runewidth syncs DefaultCondition with runewidth.EastAsianWidth only
+	// once, in its init(), so overriding it later has to be done here
+	runewidth.DefaultCondition.EastAsianWidth = wide
 }
 
 // SliceEnd returns a byte slice where the index is a rune index

internal/util/util_test.go

@@ -13,6 +13,31 @@ func TestStringWidth(t *testing.T) {
 	assert.Equal(t, 26, n)
 }
 
+func TestSetAmbiguousWidth(t *testing.T) {
+	defer SetAmbiguousWidth("auto")
+
+	// U+03B1 is ambiguous width, U+3042 is wide, U+0061 is narrow
+	bytes := []byte("\u03b1\u3042a")
+
+	SetAmbiguousWidth("single")
+	assert.Equal(t, 1, StringWidth(bytes, 1, 4))
+	assert.Equal(t, 3, StringWidth(bytes, 2, 4))
+	assert.Equal(t, 4, StringWidth(bytes, 3, 4))
+
+	SetAmbiguousWidth("double")
+	assert.Equal(t, 2, StringWidth(bytes, 1, 4))
+	assert.Equal(t, 4, StringWidth(bytes, 2, 4))
+	assert.Equal(t, 5, StringWidth(bytes, 3, 4))
+
+	// "auto" restores the width implied by the environment
+	SetAmbiguousWidth("auto")
+	expected := 1
+	if envAmbiguousWide {
+		expected = 2
+	}
+	assert.Equal(t, expected, StringWidth(bytes, 1, 4))
+}
+
 func TestSliceVisualEnd(t *testing.T) {
 	s := []byte("\thello")
 	slc, n, _ := SliceVisualEnd(s, 2, 4)

runtime/help/options.md

@@ -11,6 +11,23 @@ if you have set either of the above environment variables).
 
 Here are the available options:
 
+* `ambiguouswidth`: how wide the characters with the East Asian Ambiguous
+   width property (as defined by [Unicode Standard Annex
+   #11](https://www.unicode.org/reports/tr11)) are considered to be. These
+   characters, e.g. Greek and Cyrillic letters, accented Latin letters and box
+   drawing characters, are drawn one column wide by most terminals but two
+   columns wide by some terminals in an East Asian environment. If micro's
+   choice does not match your terminal, text is misaligned and the cursor is
+   drawn in the wrong column. This setting is `global only`.
+   * `auto`: use two columns if the locale environment variables (`LC_ALL`,
+      `LC_CTYPE`, `LANG`) indicate a Chinese, Japanese or Korean locale,
+      otherwise one column. Can be overridden with the `RUNEWIDTH_EASTASIAN`
+      environment variable.
+   * `single`: always use one column, like `wcwidth(3)` and most terminals do.
+   * `double`: always use two columns.
+
+    default value: `auto`
+
 * `autoindent`: when creating a new line, use the same indentation as the
    previous line.