#1245 Add option to highlight only sub-line

[Zufu Liu]

Currently when highlight caret line is enabled (SCI_SETCARETLINEVISIBLE(true)), all sub-lines is highlighted for wrapped line.

In some cases, it's might better to highlight only the sub-line that contains caret. So "caret line" (or "current line") refer to a on screen line that contains caret, with fixed "one line" height regardless of wrapping.

If a wrapped line contains too many sub-lines, drawing a large frame or bacground rectange may lose the purpose of highlighting.

Application like VS and VSCode only hightlight sub-line.

Related: https://sourceforge.net/p/scintilla/feature-requests/1240/

[Zufu Liu]

Please change the title to "Add new option to enable only highlight sub-line" or similar.