Add support for double-width (CJK) characters

[jnjackins]

Tested on OS X and the latest Ubuntu, using the default terminal application for each, and from a tty on Ubuntu.

Sorry for all the diff noise in width_test.go. The actual test semantics only change in TestCountGlyphs, which compares against the pre-computed testCase.glyphs rather than the length of a slice of runes.

Fixes #42

[peterh]

Thanks for the pull request.

Pulled, on the basis that it's clean, it doesn't affect what I'm doing, and it should be an improvement on the status quo even though it doesn't catch every fullwidth character.

I'm just going to point out that unicode.Katakana includes some halfwidth Katakana characters (eg. \uFF66 through \uFF9D http://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms#In_Unicode ), so those glyphs regress with this patch.

[jnjackins]

Good point. Looking at that article, it looks like there is halfwidth Katakana and Hangul, halfwidth versions of punctuation that is normally fullwidth, and fullwidth versions of ASCII characters. I'm not certain about Hangul (Korean), but at least in Japanese the halfwidth Katakana characters are used quite rarely, and I've never seen halfwidth punctuation used. I'd guess Hangul is about the same. Fullwidth latin (ASCII) characters are occasionally used in Japanese text.

Perhaps we should wait until this bothers me or someone else, and look at teaching countGlyphs about the exceptions then.

Thanks for merging!

[roachsinai]

Hi, does the double-width problem for Chinese characters have been solved?

I have a Chinese character double-width problem. :-(

[peterh]

As far as I am aware, double width characters should work. What exactly is the problem you are having?

[roachsinai]

I'm using a commandline program BaiduPCS-Go. It's a Baidu Wangpan cli write use Go. To use BaiduPCS-Go I should login use Baidu ID. And then it will show prompt my ID included. And my ID include Chinese chars.

The problem is the cursor is left shift two spaces.

Oops, you're write. May be it's not problem about Chinese characters. Because I also use two special characters: 『 and 』(『』apologize for my odd ID). Cause the policy of Baidu I can't change may Baidu ID.

[jnjackins]

I can reproduce the issue. Seems that

+var doubleWidth = []*unicode.RangeTable{
+   unicode.Han,
+   unicode.Hangul,
+   unicode.Hiragana,
+   unicode.Katakana,
+}

isn't enough.