Attempted fixes for render crashes on windows, still can't redo them here

in a virtual machine, maybe that has some different threading behavior.
Also should fix a problem with displaying render passes and multiple slots.

source/blender/blenkernel/intern/image.c

@@ -1894,13 +1894,16 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **lock_
 		memset(&rres, 0, sizeof(RenderResult));
 	
 	if(!(rres.rectx > 0 && rres.recty > 0)) {
+		if(from_render)
 			RE_ReleaseResultImage(re);
 		return NULL;
 	}
 
 	/* release is done in BKE_image_release_ibuf using lock_r */
-	if(from_render)
+	if(from_render) {
+		BLI_lock_thread(LOCK_VIEWER);
 		*lock_r= re;
+	}
 
 	/* this gives active layer, composite or seqence result */
 	rect= (unsigned int *)rres.rect32;
@@ -1909,9 +1912,9 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **lock_
 	dither= iuser->scene->r.dither_intensity;
 
 	/* get compo/seq result by default */
-	if(rres.rectf && layer==0);
+	if(rres.compo_seq && layer==0);
 	else if(rres.layers.first) {
-		RenderLayer *rl= BLI_findlink(&rres.layers, layer-(rres.rectf?1:0));
+		RenderLayer *rl= BLI_findlink(&rres.layers, layer-(rres.compo_seq?1:0));
 		if(rl) {
 			RenderPass *rpass;
 
@@ -1934,6 +1937,9 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **lock_
 		}
 	}
 
+	if(!(rectf || rect))
+		return NULL;
+
 	ibuf= image_get_ibuf(ima, IMA_NO_INDEX, 0);
 
 	/* make ibuf if needed, and initialize it */
@@ -1942,17 +1948,12 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **lock_
 		image_assign_ibuf(ima, ibuf, IMA_NO_INDEX, 0);
 	}
 
-	if(!(rectf || rect))
-		return ibuf;
-
 	ibuf->x= rres.rectx;
 	ibuf->y= rres.recty;
 	
-	if(ibuf->rect_float!=rectf || rect) { /* ensure correct redraw */
-		BLI_lock_thread(LOCK_CUSTOM1);
+	if(ibuf->rect_float!=rectf || rect) /* ensure correct redraw */
 		imb_freerectImBuf(ibuf);
-		BLI_unlock_thread(LOCK_CUSTOM1);
-	}
+
 	if(rect)
 		ibuf->rect= rect;
 	
@@ -2155,10 +2156,13 @@ ImBuf *BKE_image_acquire_ibuf(Image *ima, ImageUser *iuser, void **lock_r)
 void BKE_image_release_ibuf(Image *ima, void *lock)
 {
 	/* for getting image during threaded render / compositing, need to release */
-	if(lock == ima)
+	if(lock == ima) {
 		BLI_unlock_thread(LOCK_VIEWER); /* viewer image */
-	else if(lock)
+	}
+	else if(lock) {
 		RE_ReleaseResultImage(lock); /* render result */
+		BLI_unlock_thread(LOCK_VIEWER); /* view image imbuf */
+	}
 }
 
 ImBuf *BKE_image_get_ibuf(Image *ima, ImageUser *iuser)

source/blender/editors/render/render_internal.c

@@ -129,12 +129,8 @@ void image_buffer_rect_update(Scene *scene, RenderResult *rr, ImBuf *ibuf, volat
 	}
 	if(rectf==NULL) return;
 
-	if(ibuf->rect==NULL) {
-		BLI_lock_thread(LOCK_CUSTOM1);
 	if(ibuf->rect==NULL)
 		imb_addrectImBuf(ibuf);
-		BLI_unlock_thread(LOCK_CUSTOM1);
-	}
 
 	rectf+= 4*(rr->rectx*ymin + xmin);
 	rectc= (char *)(ibuf->rect + ibuf->x*rymin + rxmin);
@@ -505,17 +501,22 @@ static void image_renderinfo_cb(void *rjv, RenderStats *rs)
 static void image_rect_update(void *rjv, RenderResult *rr, volatile rcti *renrect)
 {
 	RenderJob *rj= rjv;
+	Image *ima= rj->image;
 	ImBuf *ibuf;
 	void *lock;
 
-	ibuf= BKE_image_acquire_ibuf(rj->image, &rj->iuser, &lock);
+	/* only update if we are displaying the slot being rendered */
+	if(ima->render_slot != ima->last_render_slot)
+		return;
+
+	ibuf= BKE_image_acquire_ibuf(ima, &rj->iuser, &lock);
 	if(ibuf) {
 		image_buffer_rect_update(rj->scene, rr, ibuf, renrect);
 
 		/* make jobs timer to send notifier */
 		*(rj->do_update)= 1;
 	}
-	BKE_image_release_ibuf(rj->image, lock);
+	BKE_image_release_ibuf(ima, lock);
 }
 
 static void render_startjob(void *rjv, short *stop, short *do_update)

source/blender/editors/space_image/image_draw.c

@@ -76,8 +76,6 @@ static void image_verify_buffer_float(SpaceImage *sima, Image *ima, ImBuf *ibuf,
 	   NOTE: if float buffer changes, we have to manually remove the rect
 	*/
 
-	if(ibuf->rect_float && ibuf->rect==NULL) {
-		BLI_lock_thread(LOCK_CUSTOM1);
 	if(ibuf->rect_float && ibuf->rect==NULL) {
 		if(color_manage) {
 			if(ima && ima->source == IMA_SRC_VIEWER)
@@ -88,8 +86,6 @@ static void image_verify_buffer_float(SpaceImage *sima, Image *ima, ImBuf *ibuf,
 
 		IMB_rect_from_float(ibuf);
 	}
-		BLI_unlock_thread(LOCK_CUSTOM1);
-	}
 }
 
 static void draw_render_info(Scene *scene, Image *ima, ARegion *ar)

source/blender/render/extern/include/RE_pipeline.h

@@ -130,6 +130,9 @@ typedef struct RenderResult {
 	/* for render results in Image, verify validity for sequences */
 	int framenr;
 
+	/* for acquire image, to indicate if it is compo/seq result */
+	int compo_seq;
+
 	/* render info text */
 	char *text;
 	

source/blender/render/intern/source/pipeline.c

@@ -1061,6 +1061,7 @@ void RE_AcquireResultImage(Render *re, RenderResult *rr)
 			rr->rectf= re->result->rectf;
 			rr->rectz= re->result->rectz;
 			rr->rect32= re->result->rect32;
+			rr->compo_seq= (rr->rectf != NULL);
 			
 			/* active layer */
 			rl= render_get_active_layer(re, re->result);