-void xr_rendering_measure (struct xr_rendering *, int *w, int *h);
-void xr_rendering_draw_all (struct xr_rendering *r, cairo_t *cr);
+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);