Bugfix #26761

Texture preview render now doesn't increment/decrement material->texture
user counts anymore. Blenders library.c code could use some overhaul
once to support data relinkage and copying around better. :)

source/blender/blenkernel/intern/material.c

@@ -245,12 +245,11 @@ Material *localize_material(Material *ma)
 	man= copy_libblock(ma);
 	BLI_remlink(&G.main->mat, man);
 
+	/* no increment for texture ID users, in previewrender.c it prevents decrement */
 	for(a=0; a<MAX_MTEX; a++) {
 		if(ma->mtex[a]) {
 			man->mtex[a]= MEM_mallocN(sizeof(MTex), "copymaterial");
 			memcpy(man->mtex[a], ma->mtex[a], sizeof(MTex));
-			/* free_material decrements! */
-			id_us_plus((ID *)man->mtex[a]->tex);
 		}
 	}
 	

source/blender/editors/render/render_preview.c

@@ -1117,11 +1117,20 @@ static void shader_preview_free(void *customdata)
 	
 	if(sp->matcopy) {
 		struct IDProperty *properties;
+		int a;
+		
 		/* node previews */
 		shader_preview_updatejob(sp);
 		
 		/* get rid of copied material */
 		BLI_remlink(&pr_main->mat, sp->matcopy);
+		
+		/* free_material decrements texture, prevent this. hack alert! */
+		for(a=0; a<MAX_MTEX; a++) {
+			MTex *mtex= sp->matcopy->mtex[a];
+			if(mtex && mtex->tex) mtex->tex= NULL;
+		}
+		
 		free_material(sp->matcopy);
 
 		properties= IDP_GetProperties((ID *)sp->matcopy, FALSE);