#### Xft Fonts and Rendering

The Xft library is a library for displaying fonts on the X window system; internally it uses the fontconfig library to locate font files, and the FreeType library to load and render fonts. The Xft backend is the recommended Pango font backend for screen display with X. (The Cairo back end is another possibility.)

Using the Xft backend is generally straightforward; `pango_xft_get_context()` creates a context for a specified display and screen. You can then create a `PangoLayout` with that context and render it with `pango_xft_render_layout()`. At a more advanced level, the low-level fontconfig options used for rendering fonts can be affected using `pango_xft_set_default_substitute()`, and `pango_xft_substitute_changed()`.

A range of functions for drawing pieces of a layout, such as individual layout lines and glyphs strings are provided. You can also directly create a `PangoXftRenderer`. Finally, in some advanced cases, it is useful to derive from `PangoXftRenderer`. Deriving from `PangoXftRenderer` is useful for two reasons. One reason is be to support custom attributes by overriding `PangoRendererClass` virtual functions like ‘prepare_run’ or ‘draw_shape’. The other reason is to customize exactly how the final bits are drawn to the destination by overriding the `PangoXftRendererClass` virtual functions ‘composite_glyphs’ and ‘composite_trapezoids’.