display_manager ->fonts_changed: Reload all fonts and recompute and redraw all windows of all frames.
Send this after changing font.scale, font.pango_families
or
font.system_fonts
at runtime, or after changing a theme_font.
Font objects keep their
identity: only their size and Pango family change, so all their users
see the change. If font.system_fonts
or font.user_fonts changed, the font aliases
are updated.
Everything that shows text is recomputed, dialogs are laid out again
and frames resize their windows. A frame or graphical whose class
defines display_manager->fonts_changed
is sent this message, so it can drop what it computed from the font
metrics. A graphical gets this after its contents were recomputed.
Classes editor, menu_bar, text and tab define it.
