Guile-Cairo README Last updated 18 May 2007. About Guile-Cairo ================= Guile-Cairo wraps the Cairo graphics library for Guile Scheme. A pasteable introduction to using Guile-Cairo ============================================= ;; Paste this into your guile interpreter! ;; This wrapset defines a module `(cairo)' (use-modules (cairo)) ;; Cairo procedures all start with `cairo-' (cairo-version-string) ;; => "1.4.2" ;; For most useful things, you have to make a surface first (define surf (cairo-image-surface-create 'argb32 140 100)) ;; Given a surface, you can create a cairo context, and start drawing (define cr (cairo-create surf)) ;; You then need to make a source (cairo-select-font-face cr "Bitstream Vera Sans" 'normal 'normal) (cairo-scale cr 100 100) (define pat (cairo-pattern-create-linear 0 0 1 1)) (cairo-pattern-add-color-stop-rgba pat 1 1 0 0 1) (cairo-pattern-add-color-stop-rgba pat 0 0 0 1 1) (cairo-set-source cr pat) ;; Then you make your mask (cairo-set-font-size cr 0.4) (cairo-move-to cr 0.0 0.6) (cairo-show-text cr "(cairo)") ;; Finally you can write the surface out to a file if you want (cairo-surface-write-to-png surf "/tmp/guile-cairo.png") ;; Functions that write out to files always take the filename as their ;; last argument, which is optional. If you leave it out, guile-cairo ;; will write to the current output port. So this is another way of ;; doing the same thing: (with-output-to-file "/tmp/guile-cairo.png" (lambda () (cairo-surface-write-to-png surf))) ;; Enumerated types are represented as symbols. The available set of ;; symbols for any given type can be retrieved at runtime (cairo-format-get-values) ;; => (argb32 rgb24 a8 a1) ;; That's it! Notes ===== Guile-Cairo wraps almost all of Cairo's procedures. Notable exceptions include functions that read or write from streams instead of files and raw access to image data. Guile-Cairo wraps all of Cairo's types. As mentioned above, enumerated values are represented by symbols, but functions accept integers as well. Struct types like cairo_rectangle_t are represented as vectors. Constructors of the form cairo-make-rectangle are provided, as well as accessors like cairo-rectangle:x. Using Guile-Cairo's C interface =============================== These days Cairo forms a part of many software stacks; its types are seen in the APIs of a number of other libraries. Guile-Cairo provides an interface to represent all cairo C types as scheme values. To build against this library in your C program, first you will need to get the CFLAGS and LDFLAGS to link against libguile-cairo. Autoconf users should use: PKG_CHECK_MODULES(GUILE_CAIRO, guile-cairo >= 1.3.0) AC_SUBST(GUILE_CAIRO_CFLAGS) AC_SUBST(GUILE_CAIRO_LDFLAGS) In your C files you should then: #include <guile-cairo.h> The type wrapping functions are all in the form scm_to_TYPE and scm_from_TYPE, where TYPE could be cairo_surface, for example. For vector types there is also scm_fill_TYPE, which expects you to have an already-allocated structure to fill. Additionally there are scm_take_TYPE functions that will take ownership of the pointer in question, for example for constructors and for non-refcounted opaque objects like cairo_font_options_t. Copying Guile-Cairo =================== Distribution of Guile-Cairo is under the LGPL. See the COPYING file for more information. Contact info ============ Mailing List: guile-user@gnu.org Homepage: http://home.gna.org/guile-cairo/ Download: http://home.gna.org/guile-cairo/download/ Build dependencies ================== * Guile 1.8.0 or newer http://www.gnu.org/software/guile/ * Cairo 1.2.0 or newer http://cairographics.org/ Installation quickstart ======================= Install using the standard autotools incantation: ./configure --prefix=/opt/guile-cairo && make && make install. Build from CVS or Arch using ./autogen.sh --prefix=/opt/guile-cairo && make. You can run without installing, just run './env guile'. Copying this file ================= Copyright (C) 2007 Andy Wingo <wingo pobox.com> Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.
