Description:
When I use a font, which doesn't contain all glyphs I use 
or 
if a document uses a font, which is not installed on my system,
so LO usually shows all glyphs using another font.
But there is no warning about it, also I don't get any information about, which glyphs are replaced and which font is used instead.

Steps to Reproduce:
1. Use the unicode letter number 1D4DB (html: &#120027 or &#x1D4DB )
2. Use DejaVu Sans
3. Use the same letter in a LO-math-formula in writer

Actual Results:
in Text LO uses an ugly glyph
in math-formula as a variable LO uses a nice glyph
in math-formula as text LO uses the ugly glyph see above


Expected Results:
a „warning“ (changing background color for glyphs with font replacement e.g.) and information about the font used instead the desired one (in formatting bar or as popup or ... or at least explaining in LO-help how to get this information)

also the possibility to define replacement suggestions would be nice


Reproducible: Always


User Profile Reset: No



Additional Info:
1.this is a bug for years already, 

2. the example given above is just for one glyph missing in one font, but similar things happen for whole texts using fonts, that aren't installed on a system,

3. the „nice“ glyph should be included in LO-math as setL (as setR, setN are defined)