til: simplify and clarify module_render_fragment()

This consolidates the prepare_frame+render_fragment
potentially-threaded branch but more importantly introduces some
asserts codifying the whole prepare_frame() must return a
fragmenter /and/ be accompanied by a render_fragment().

Any single-threaded modules are expected to just populate
render_fragment() and leave prepare_frame() unused.

1 files changed, 14 insertions, 11 deletions

diff --git a/src/til.c b/src/til.c
index 00b73f6..478d43e 100644
--- a/src/til.c
+++ b/src/til.c
@@ -173,24 +173,27 @@ static void module_render_fragment(til_module_context_t *context, til_threads_t
 
 	module = context->module;
 
-	if (context->n_cpus > 1 && module->prepare_frame) {
+	if (module->prepare_frame) {
 		til_frame_plan_t	frame_plan = {};
 
 		module->prepare_frame(context, ticks, fragment, &frame_plan);
 
-		if (module->render_fragment) {
+		/* XXX: any module which provides prepare_frame() must return a frame_plan.fragmenter,
+		 * and provide render_fragment()
+		 */
+		assert(frame_plan.fragmenter);
+		assert(module->render_fragment);
+
+		if (context->n_cpus > 1) {
 			til_threads_frame_submit(threads, fragment, &frame_plan, module->render_fragment, context, ticks);
 			til_threads_wait_idle(threads);
-		}
-	} else if (module->prepare_frame) {
-		til_frame_plan_t	frame_plan = {};
-		unsigned		fragnum = 0;
-		til_fb_fragment_t	frag;
-
-		module->prepare_frame(context, ticks, fragment, &frame_plan);
+		} else {
+			unsigned		fragnum = 0;
+			til_fb_fragment_t	frag;
 
-		while (frame_plan.fragmenter(context, fragment, fragnum++, &frag))
-			module->render_fragment(context, ticks, 0, &frag);
+			while (frame_plan.fragmenter(context, fragment, fragnum++, &frag))
+				module->render_fragment(context, ticks, 0, &frag);
+		}
 	} else if (module->render_fragment)
 		module->render_fragment(context, ticks, 0, fragment);