Completely support full-width characters in differential rendering

[tompng]

When dialog is cleared, we need to restore the text that was hidden behind dialogs.

To implement restoring full width characters hidden behind dialog, Reline::Unicode.take_range lacks of feature.
It does not provide where to render the string. column information is missing.

Reline::Unicode.take_range('一二三四五a', 2, 5) #=> '二三' # should render at column=2
Reline::Unicode.take_range('a一二三四五', 2, 5) #=> '二三' # should render at column=3

Sometimes we need other cut variation depending on adjacent dialog position.
The image below shows a variation of take_range('一二三四五六七八九', 5, 8, option)

So I add Reline::Unicode.take_mbchar_range that has option cover_begin, cover_end, padding and make it return the actual cut position.

take_mbchar_range('一二三', 1, 4) #=> ['二', 2, 2]
take_mbchar_range('一二三', 1, 4, cover_begin: true) #=> ['一二', 0, 4]
take_mbchar_range('一二三', 1, 4, cover_end: true) #=> ['二三', 2, 4]
take_mbchar_range('一二三', 1, 4, padding: true) #=> [' 二 ', 1, 4]
take_mbchar_range('一二三', 1, 4, cover_begin: true, padding: true) #=> ['一二 ', 0, 5]
take_mbchar_range('一二三', 1, 4, cover_end: true, padding: true) #=> [' 二三', 1, 5]

# Padding space can have different background color
take_mbchar_range("#{RED_BACKGROUND}一#{BLUE_BACKGROUND}二#{GREEN_BACKGROUND}三", 1, 4, padding: true)
#=> "#{RED_BACKGROUND} #{BLUE_BACKGROUND}二#{GREEN_BACKGROUND} "

[ima1zumi]

Could you add comments to these conditional branches?

[tompng]

I forgot to implement this.

# Red background あ
Reline::Unicode.take_mbchar_range "\e[41mあ", 1, 2, padding: true
# Red background whitespace + No background whitespace
["\e[41m \e[0m ", 1, 2]

I've updated the implementation and add comments

[ima1zumi]

I'm curious, why did you combine calculating padding with take_mbchar_range?

[tompng]

Padding sometimes have background colors.
The last testcase I added is a good example.

assert_equal ["\e[41m \e[42mい\e[43m ", 1, 4], Reline::Unicode.take_mbchar_range("\e[41mあ\e[42mい\e[43mう\e[0m", 1, 4, padding: true)

So we can't add non-colored space as padding. Padding logic cannot be separated from take_mbchar_range

[ima1zumi]

LGTM!