Change: Support side-by-side fallback FontCaches instead of hierarchical. (#13303)

The text layouter system can now support using different fonts for different glyphs, including mixing scalable and sprite glyphs.

src/zoom_func.h

@@ -119,4 +119,14 @@ inline int ScaleGUITrad(int value)
 	return value * _gui_scale / 100;
 }
 
+/**
+ * Scale traditional pixel dimensions to font zoom level, for drawing sprite fonts.
+ * @param value Pixel amount at #ZOOM_BASE (traditional "normal" interface size).
+ * @return Pixel amount at _font_zoom (current interface size).
+ */
+inline int ScaleFontTrad(int value)
+{
+	return UnScaleByZoom(value * ZOOM_BASE, _font_zoom);
+}
+
 #endif /* ZOOM_FUNC_H */