It is said that fontconfig should be used for font fallback, but it seems that terminal emulators are not always using this recommended API for font fallback.

• kitty uses fontconfig only for retrieving the set of all fonts, then filters and prioritizes manually)
• wezterm seems to only support font fallback based on what the user has provided in the configs.
• What is konsole, gnome-terminal and alacritty doing?
• Not all fontconfig system configurations seem to be reliable (if any at all).

On top of using fontconfig for getting the list of fallback fonts maybe we could provide a manually provided list of font fallbacks too.

• Evaluate the usefulness of selecting font files based on codepoints / codepoint sequences (such as kitty does provide)
• Evaluate embedding Powerline glyphs (should be configurable, too)
• Evaluate embedding box drawing glyphs (should be configurable, too)