[cairo] _cairo_scaled_font_is_frozen(scaled_font) assertion failure with freetype on win32-printing surface

[Kozhevnikov Mikhail]

Hi,

Could someone explain the basic workflow for text rendering with scaled fonts? 

Currently, I have two faces in TrueType files. I load them using Freetype, pass to cairo_ft_font_face_create_for_ft_face(), then assign the source FT_Face-s as user data with FT_Done_Face as destroy function, create several instances of scaled font for each of the faces (of different size) and do the rendering. 
I works fine for surfaces but the win32-printing one. In the latter case an assertion fails with _cairo_scaled_font_is_frozen(scaled_font) expression. I've tried locking the font each time before setting it, but it seems to make no different. Could you explain what's wrong here and how should one use the font locking mechnism?

Thanks in advance,
Mikhail.