Fix #35979, #35937, #35739: undo crashes and missing updates with blender

internal viewport rendering. Lots of tweaks here, mainly:

* Stop 3D viewport render and free database before undo.
* Accumulate update flags rather than replace them each time it rerenders, to
  avoid previous updates getting lost.
* Don't check against Render struct view parameters for changes, those are set
  in the job thread which might not run before the next update call.

2 files changed, 19 insertions, 3 deletions

diff --git a/source/blender/render/extern/include/RE_engine.h b/source/blender/render/extern/include/RE_engine.h
index b6c3668512b..786c67f5305 100644
--- a/source/blender/render/extern/include/RE_engine.h
+++ b/source/blender/render/extern/include/RE_engine.h
@@ -70,6 +70,7 @@ struct Scene;
 /* RenderEngine.update_flag, used by internal now */
 #define RE_ENGINE_UPDATE_MA			1
 #define RE_ENGINE_UPDATE_OTHER		2
+#define RE_ENGINE_UPDATE_DATABASE	4
 
 extern ListBase R_engines;
 
@@ -97,7 +98,7 @@ typedef struct RenderEngine {
 	RenderEngineType *type;
 	void *py_instance;
 
-	int flag, update_flag;
+	int flag;
 	struct Object *camera_override;
 
 	int tile_x;
@@ -110,6 +111,15 @@ typedef struct RenderEngine {
 	int resolution_x, resolution_y;
 
 	struct ReportList *reports;
+
+	/* for blender internal only */
+	int update_flag;
+	int job_update_flag;
+
+	rctf last_viewplane;
+	rcti last_disprect;
+	float last_viewmat[4][4];
+	int last_winx, last_winy;
 } RenderEngine;
 
 RenderEngine *RE_engine_create(RenderEngineType *type);
diff --git a/source/blender/render/intern/source/convertblender.c b/source/blender/render/intern/source/convertblender.c
index bd2d292f633..ce71ab188a9 100644
--- a/source/blender/render/intern/source/convertblender.c
+++ b/source/blender/render/intern/source/convertblender.c
@@ -4863,7 +4863,11 @@ static void init_render_object(Render *re, Object *ob, Object *par, DupliObject
 void RE_Database_Free(Render *re)
 {
 	LampRen *lar;
-	
+
+	/* will crash if we try to free empty database */
+	if (!re->i.convertdone)
+		return;
+
 	/* statistics for debugging render memory usage */
 	if ((G.debug & G_DEBUG) && (G.is_rendering)) {
 		if ((re->r.scemode & (R_BUTS_PREVIEW|R_VIEWPORT_PREVIEW))==0) {
@@ -5399,8 +5403,10 @@ void RE_Database_Preprocess(Render *re)
 				volume_precache(re);
 	}
 	
-	if (re->test_break(re->tbh))
+	if (re->test_break(re->tbh)) {
+		re->i.convertdone = TRUE;
 		RE_Database_Free(re);
+	}
 	else
 		re->i.convertdone = TRUE;