*: add module context machinery

introduces create_context() and destroy_context() methods, and adds a
'void *context' first parameter to the module methods.

If a module doesn't supply create_context() then NULL is simply passed
around as the context, so trivial modules can continue to only implement
render_fragment().

A subsequent commit will update the modules to encapsulate their global
state in module-specific contexts.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/rototiller.h b/src/rototiller.h
index d1578fb..933f733 100644
--- a/src/rototiller.h
+++ b/src/rototiller.h
@@ -12,8 +12,10 @@ typedef struct rototiller_frame_t {
 } rototiller_frame_t;
 
 typedef struct rototiller_module_t {
-	void	(*prepare_frame)(unsigned n_cpus, fb_fragment_t *fragment, rototiller_frame_t *res_frame);
-	void	(*render_fragment)(fb_fragment_t *fragment);
+	void *	(*create_context)(void);
+	void	(*destroy_context)(void *context);
+	void	(*prepare_frame)(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_frame_t *res_frame);
+	void	(*render_fragment)(void *context, fb_fragment_t *fragment);
 	char	*name;
 	char	*description;
 	char	*author;