(: render-glyph-solid
   (ttf:font string sdl2:color -> sdl2:surface))
(define (render-glyph-solid font glyph fg)
  (set-finalizer! (render-glyph-solid* font glyph fg) free-surface!))

(: render-glyph-solid*
   (ttf:font string sdl2:color -> sdl2:surface))
(define (render-glyph-solid* font glyph fg)
  (let* ((glyph-int (%glyph->Uint16 glyph 'render-glyph-solid*))
         (surf (TTF_RenderGlyph_Solid font glyph-int fg)))
    (if (%nonnull-surface? surf)
        surf
        (abort (sdl-failure "TTF_RenderGlyph_Solid" #f)))))