Font quality

[Neil Hodgson]

The wxWidgets implementation of Scintilla wxStyledTextCtrl has an
additional parameter 'extraFontFlag' which appears to be used to
determine whether to enable font anti-aliasing. A request
(https://sourceforge.net/tracker/?func=detail&atid=352439&aid=2812250&group_id=2439)
has recently been made to add some way to force ClearType font
anti-aliasing mode on Windows. Other platforms may have similar
settings.

It would help interoperability and minimize code if a single
mechanism was defined for these settings. The Windows feature used to
control this is called quality (see LOGFONT:
http://msdn.microsoft.com/en-us/library/dd145037%28VS.85%29.aspx) and
takes a value from an enumerated set. Scintilla could expose a similar
concept, replacing extraFontFlag and allowing a set of
platform-independent values (default, no-anti-alias, anti-alias,
lcd-specific) which would be passed through to the closest platform
equivalent along with any needed platform-specific values.

Neil