RenderEngine: steps towards implementation of this proposal:

http://wiki.blender.org/index.php/Dev:2.6/Source/Render/RenderEngineAPI

* RenderEngine is now a persistent python object that exists and retains
  properties as long as a frame is being rendered. This is mostly useful now
  that more than one callback will be added.
* Added update() callback that should ideally be used to export the scene,
  leaving only the rendering to the render() callback. This is not required to
  be used at this point, but separating this will make things more thread safe
  later on.
* Added tag_redraw() and tag_update() functions that will be used for viewport
  rendering.
* Internal change: status text is now retained after update_status calls.

2 files changed, 33 insertions, 4 deletions

diff --git a/source/blender/render/extern/include/RE_engine.h b/source/blender/render/extern/include/RE_engine.h
index 344ef301f4c..b848dc26681 100644
--- a/source/blender/render/extern/include/RE_engine.h
+++ b/source/blender/render/extern/include/RE_engine.h
@@ -55,6 +55,8 @@ struct Scene;
 /* RenderEngine.flag */
 #define RE_ENGINE_ANIMATION		1
 #define RE_ENGINE_PREVIEW		2
+#define RE_ENGINE_DO_DRAW		4
+#define RE_ENGINE_DO_UPDATE		8
 
 extern ListBase R_engines;
 
@@ -66,6 +68,7 @@ typedef struct RenderEngineType {
 	char name[64];
 	int flag;
 
+	void (*update)(struct RenderEngine *engine, struct Main *bmain, struct Scene *scene);
 	void (*render)(struct RenderEngine *engine, struct Scene *scene);
 
 	/* RNA integration */
@@ -74,11 +77,13 @@ typedef struct RenderEngineType {
 
 typedef struct RenderEngine {
 	RenderEngineType *type;
+	void *py_instance;
 
 	int flag;
 
 	struct Render *re;
 	ListBase fullresult;
+	char *text;
 } RenderEngine;
 
 RenderEngine *RE_engine_create(RenderEngineType *type);
diff --git a/source/blender/render/intern/source/external_engine.c b/source/blender/render/intern/source/external_engine.c
index a6214329d0e..9d48e257154 100644
--- a/source/blender/render/intern/source/external_engine.c
+++ b/source/blender/render/intern/source/external_engine.c
@@ -61,7 +61,7 @@
 static RenderEngineType internal_render_type = {
 	NULL, NULL,
 	"BLENDER_RENDER", "Blender Render", RE_INTERNAL,
-	NULL,
+	NULL, NULL,
 	{NULL, NULL, NULL}};
 
 #ifdef WITH_GAMEENGINE
@@ -69,7 +69,7 @@ static RenderEngineType internal_render_type = {
 static RenderEngineType internal_game_type = {
 	NULL, NULL,
 	"BLENDER_GAME", "Blender Game", RE_INTERNAL|RE_GAME,
-	NULL,
+	NULL, NULL,
 	{NULL, NULL, NULL}};
 
 #endif
@@ -125,6 +125,15 @@ RenderEngine *RE_engine_create(RenderEngineType *type)
 
 void RE_engine_free(RenderEngine *engine)
 {
+#ifdef WITH_PYTHON
+	if(engine->py_instance) {
+		BPY_DECREF(engine->py_instance);
+	}
+#endif
+
+	if(engine->text)
+		MEM_freeN(engine->text);
+
 	MEM_freeN(engine);
 }
 
@@ -216,6 +225,19 @@ void RE_engine_update_stats(RenderEngine *engine, const char *stats, const char
 		re->i.infostr= NULL;
 		re->i.statstr= NULL;
 	}
+
+	/* set engine text */
+	if(engine->text) {
+		MEM_freeN(engine->text);
+		engine->text= NULL;
+	}
+
+	if(stats && stats[0] && info && info[0])
+		engine->text= BLI_sprintfN("%s | %s", stats, info);
+	else if(info && info[0])
+		engine->text= BLI_strdup(info);
+	else if(stats && stats[0])
+		engine->text= BLI_strdup(stats);
 }
 
 void RE_engine_update_progress(RenderEngine *engine, float progress)
@@ -273,8 +295,10 @@ int RE_engine_render(Render *re, int do_all)
 	if((re->r.scemode & (R_NO_FRAME_UPDATE|R_PREVIEWBUTS))==0)
 		scene_update_for_newframe(re->main, re->scene, re->lay);
 
-	type->render(engine, re->scene);
-
+	if(type->update)
+		type->update(engine, re->main, re->scene);
+	if(type->render)
+		type->render(engine, re->scene);
 
 	free_render_result(&engine->fullresult, engine->fullresult.first);