[Fontconfig] How to block glyph fallback in a QT application?

[Janusz S. Bien]

Quote/Cytat - "Janusz S. Bien" <jsbien at mimuw.edu.pl> (Mon 06 Jan 2014  
04:58:44 PM CET):

>> Gucharmap has an option to turn off fallback, and so does Pango, but for
>> a Qt application you will need a Qt solution.

For archive, I've found

http://harmattan-dev.nokia.com/docs/platform-api-reference/xml/daily-docs/libqt4/qfont.html

"QFont::NoFontMerging	0x8000	If the font selected for a certain  
writing system does not contain a character requested to draw, then Qt  
automatically chooses a similar looking font that contains the  
character. The NoFontMerging flag disables this feature. Please note  
that enabling this flag will not prevent Qt from automatically picking  
a suitable font when the selected font does not support the writing  
system of the text."

and

https://bugreports.qt-project.org/browse/QTBUG-9816

"Add style strategy to QFont to turn off automatic font resolution completely

The QFont::NoFontMerging flag turns off font merging within a single  
script item, but still allows automatically picking different fonts  
for each script item if the currently selected font does not support  
the script in question."

I would appreciate very much your comments to the quoted passages:  
what is the meaning of "script" or "writing system" in this context?  
How the system can check whether the font supports a given script or  
not? Is it a property of a font? If so, how is it encoded?

Best regards

Janusz

-- 
Prof. dr hab. Janusz S. Bień -  Uniwersytet Warszawski (Katedra  
Lingwistyki Formalnej)
Prof. Janusz S. Bień - University of Warsaw (Formal Linguistics Department)
jsbien at uw.edu.pl, jsbien at mimuw.edu.pl, http://fleksem.klf.uw.edu.pl/~jsbien/