bug#20984: 25.0.50; Combining accents don't display properly in certain fonts

[Eli Zaretskii]

> Date: Sun, 5 Jul 2015 17:24:32 +0100
> From: Artur Malabarba <bruce.connor.am@gmail.com>
> 
> Start emacs -Q then evaluate the following in the *scratch* (assuming
> you have this font installed)
> 
> (set-face-attribute 'default nil :font "SourceCodePro Medium")
> (insert (format "a%c" 768))
> 
> The result should look like "à", but instead, it looks like "a`" where
> the letter "a" is actually distorted and shifted up (image attached).
> The same happens with other combining symbols.

Do both glyphs come from the same font, according to "C-u C-x ="?  (I
don't have that font installed to try that myself.)

Emacs can only compose characters if their glyphs are covered by the
same font.