
UP DOWN LEFT RIGHT	Move cursor
Shift+UP DOWN 		Page Up/Page Down (move cursor by 4 lines)
Shift+LEFT RIGHT	Home/End (move cursor to Line Start/End)
Backspace			Delete character before cursor
Enter				Go to next line (preserve indent)
Shift+Enter			Break current line
Ctrl+Enter			Insert a line after current line

Ctrl-C				Copy current line to buffer
Ctrl-K				Delete current line, move to buffer
Ctrl-Backspace		Clear current line, move to buffer
Ctrl-U				Undelete a line (paste a line from buffer)

Backspace at line start		Merge two lines



Enter:
Next line	Action
Not empty	Move cursor to start position (first non-space character) of next line
Empty		Move cursor to next line, indent with the same spaces as on previous line


Ctrl+Enter:
If last line of the screen is empty
	then	Insert a empty line after current line, then invoke Enter
	else	invoke Enter

Shift+Enter:
If last line of the screen is empty
	then	break current line at cursor, indent, then invoke Enter
	else	invoke Enter

Enter: 
如果当前行不为空（不全是空格）
	则		转下一行行首空格数与当前行相同
	否则	转下一行，回到行首



Ctrl+Enter:
如果最后一行为空（全是空格）
	则		在当前行后插入一行，然后转下一行（执行Enter）
	否则		直接转下一行（执行Enter）

Shift+Enter:
如果最后一行为空
	则		在当前行当前位置断行，光标后内容按照Enter规则转下一行
	否则		直接转下一行（执行Enter）

Ctrl-K:
删除当前行，下一行上移

use words: fill, move
