void xr_rendering_measure (const struct xr_rendering *, int *w, int *h);
void xr_rendering_draw (struct xr_rendering *r, cairo_t *cr,
int x0, int y0, int x1, int y1);
void xr_rendering_measure (const struct xr_rendering *, int *w, int *h);
void xr_rendering_draw (struct xr_rendering *r, cairo_t *cr,
int x0, int y0, int x1, int y1);