[cairo] Implement pluggable appearance renderers.

A ccss-cairo consumer can install an appearance rendering module
into the plugin directory and refer to the drawing functions
from the CSS.

For the CSS statement

	box {
		appearance: custom_box example-8;
	}

the module "libexample-8.so" is loaded, and the symbol "custom_box()"
is invoked for rendering.

2 files changed, 129 insertions, 0 deletions

diff --git a/examples/Makefile.am b/examples/Makefile.am
index 2baa97c..93f21b1 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -5,6 +5,7 @@ AM_CPPFLAGS = \
 	-I$(top_builddir) \
 	-I$(top_srcdir) \
 	$(CCSS_EXAMPLES_CFLAGS) \
+	-DCCSS_CAIRO_APPEARANCE_MODULE_INTERFACE_VERSION=\"$(CCSS_CAIRO_APPEARANCE_MODULE_INTERFACE_VERSION)\" \
 	$(NULL)
 
 AM_LDFLAGS = \
@@ -22,8 +23,14 @@ noinst_PROGRAMS = \
 	example-4-2 \
 	example-6 \
 	example-7 \
+	example-8 \
 	$(NULL)
 
+noinst_LTLIBRARIES = libexample-8-noinst.la
+
+pkglibdir = $(CCSS_CAIRO_APPEARANCE_MODULE_PATH)
+pkglib_LTLIBRARIES = libexample-8.la
+
 if CCSS_WITH_SOUP
 noinst_PROGRAMS += example-5
 endif
@@ -46,6 +53,15 @@ example_6_SOURCES = example-6.c
 
 example_7_SOURCES = example-7.c
 
+libexample_8_noinst_la_LDFLAGS = -module -no-undefined
+libexample_8_noinst_la_SOURCES = example-8.c
+
+example_8_SOURCES = 
+example_8_LDADD = libexample-8-noinst.la
+
+libexample_8_la_LDFLAGS = -avoid-version -export-dynamic -module -no-undefined
+libexample_8_la_SOURCES = example-8.c
+
 EXTRA_DIST = \
 	example-3.png \
 	example-5.svg \
diff --git a/examples/example-8.c b/examples/example-8.c
new file mode 100644
index 0000000..cb098f0
--- /dev/null
+++ b/examples/example-8.c
@@ -0,0 +1,113 @@
+/* vim: set ts=8 sw=8 noexpandtab: */
+
+#include <stdlib.h>
+#include <cairo.h>
+#include <ccss-cairo/ccss-cairo.h>
+#include <gtk/gtk.h>
+#include "config.h"
+
+/*
+ * ccss-cairo appearance module interface.
+ */
+
+G_MODULE_EXPORT char const *
+ccss_appearance_module_get_interface_version (void);
+
+G_MODULE_EXPORT void
+custom_box (ccss_style_t const	*self,
+	    cairo_t		*cr,
+	    int			 x,
+	    int			 y,
+	    int			 width,
+	    int			 height);
+
+G_MODULE_EXPORT char const *
+ccss_appearance_module_get_interface_version (void)
+{
+	return CCSS_CAIRO_APPEARANCE_MODULE_INTERFACE_VERSION;
+}
+
+G_MODULE_EXPORT void
+custom_box (ccss_style_t const	*self,
+	    cairo_t		*cr,
+	    int			 x,
+	    int			 y,
+	    int			 width,
+	    int			 height)
+{
+	cairo_rectangle (cr, x, y, width, height);
+	cairo_set_line_width (cr, 3);
+	cairo_set_line_cap (cr, CAIRO_LINE_JOIN_MITER);
+	cairo_stroke (cr);
+}
+
+/*
+ * Example binary.
+ */
+
+static gboolean
+expose_cb (GtkWidget		*widget,
+	   GdkEventExpose	*event,
+	   ccss_style_t const	*style)
+{
+	cairo_t *cr;
+
+	cr = gdk_cairo_create (widget->window);
+
+	ccss_cairo_style_draw_rectangle (style, cr, 
+					 widget->allocation.x + 10,
+					 widget->allocation.y + 10,
+					 widget->allocation.width - 20, 
+					 widget->allocation.height - 20);
+
+	cairo_destroy (cr);
+
+	return FALSE;
+}
+
+static char const _css[] = "				\
+	box { 						\
+		appearance: custom_box example-8;	\
+	}						\
+";
+
+int
+main (int	  argc,
+      char	**argv)
+{
+	ccss_grammar_t		*grammar;
+	ccss_stylesheet_t	*stylesheet;
+	ccss_style_t		*style;
+	GtkWidget		*window;
+
+	gtk_init (&argc, &argv);
+
+	grammar = ccss_cairo_grammar_create ();
+	stylesheet = ccss_grammar_create_stylesheet_from_buffer (grammar,
+							_css, sizeof (_css),
+							NULL);
+
+	style = ccss_stylesheet_query_type (stylesheet, "box");
+	g_assert (style);
+
+#ifdef CCSS_DEBUG
+	ccss_style_dump (style);
+#endif
+	window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+	gtk_window_set_default_size (GTK_WINDOW (window), 160, 90);
+	gtk_widget_set_app_paintable (window, TRUE);
+	g_signal_connect (G_OBJECT (window), "delete-event", 
+			  G_CALLBACK (gtk_main_quit), NULL);
+	g_signal_connect (G_OBJECT (window), "expose-event", 
+			  G_CALLBACK (expose_cb), style);
+
+	gtk_widget_show_all (window);
+	gtk_main ();
+
+	ccss_style_destroy (style);
+	ccss_stylesheet_destroy (stylesheet);
+	ccss_grammar_destroy (grammar);
+
+	return EXIT_SUCCESS;
+}
+