The width of Box-drawing characters

[NonerKao]

Check this for the definition of box-drawing (BD below) characters.

I found that these characters are defined to be of ambiguous width, so passing these to RuneWidth returns 2 in my environment. This is somehow inconvenient since AFAIK, terminal fonts tend to interpret BD characters in half-width.

Is it possible to remove these characters from the ambiguous table? I can make the PR if you think this sounds sane.

Thanks.

[mattn]

It is depend on $LANG. And you can modify it to set EastAsianWidth.

[mattn]

Now I added environment variable github.com/mattn/go-runewidth#IsEastAsian. You can modify it if you want to change behaivor.

[NonerKao]

Thanks for the quick reply.

Just a feedback for this patch: for some shell, such as sh or bash, github.com/mattn/go-runewidth#IsEastAsian is not a valid name for environment variable.

[mattn]

renamed to RUNEWIDTH_EASTASIAN.

[nzlov]

Hi @mattn, When LC_CTYPE=zh_CN.UTF-8, RUNEWIDTH_EASTASIAN is invalid. Box-drawing (BD below) characters, RuneWidth returns 2

[mattn]

What character do you mean?

=│=
=AA=

Please try to paste above text on your terminal. This is my environment. UNIX.

And Windows cmd.exe

[nzlov]

LC_CTYPE=zh_CN.UTF-8 RUNEWIDTH_EASTASIAN=0:

LC_CTYPE=en_US.UTF-8:

Macos 10.12.6 zh_CN iterm2 zsh

=│=
=AA=

[mattn]

Do you want to forcibly disable RUNEWIDTH_EASTASIAN ?

[mattn]

How about this patch ?

diff --git a/runewidth.go b/runewidth.go
index 70de0dc..82568a1 100644
--- a/runewidth.go
+++ b/runewidth.go
@@ -4,12 +4,21 @@ import "os"
 
 var (
 	// EastAsianWidth will be set true if the current locale is CJK
-	EastAsianWidth = os.Getenv("RUNEWIDTH_EASTASIAN") == "1" || IsEastAsian()
+	EastAsianWidth bool
 
 	// DefaultCondition is a condition in current locale
 	DefaultCondition = &Condition{EastAsianWidth}
 )
 
+func init() {
+	env := os.Getenv("RUNEWIDTH_EASTASIAN")
+	if env == "" {
+		EastAsianWidth = IsEastAsian()
+	} else {
+		EastAsianWidth = env == "1"
+	}
+}
+
 type interval struct {
 	first rune
 	last  rune

[nzlov]

Good idea, but why not force return 1?

[mattn]

What do you mean "return"?

[nzlov]

I want to remove these characters box-drawing from the ambiguous table

[mattn]

Unfortunately, box-drawing characters are listed in ambiguous width characters.

http://www.unicode.org/reports/tr11-2/

[nzlov]

@mattn Ok,thanks.