Fix T49826: NEW-DEPSGRAPH - Texture is not updated after changing its space color

The issue was caused by image ID nodes not being in the depsgraph.

Now, tricky part: we only add nodes but do not add relations yet. Reasoning:

- It's currently important to only call editor's ID update callback to solve
  the issue, without need to flush changes somewhere deeper.

- Adding relations might cause some unwanted updates, so will leave that for
  a later investigation.

2 files changed, 30 insertions, 2 deletions

diff --git a/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc b/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
index befc1ea3b7f..d1469e850e6 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
@@ -1180,6 +1180,9 @@ void DepsgraphNodeBuilder::build_nodetree(DepsNode *owner_node, bNodeTree *ntree
 			else if (id_type == ID_TE) {
 				build_texture(owner_node, (Tex *)id);
 			}
+			else if (id_type == ID_IM) {
+				build_image((Image *)id);
+			}
 			else if (bnode->type == NODE_GROUP) {
 				bNodeTree *group_ntree = (bNodeTree *)id;
 				if ((group_ntree->id.tag & LIB_TAG_DOIT) == 0) {
@@ -1238,10 +1241,33 @@ void DepsgraphNodeBuilder::build_texture(DepsNode *owner_node, Tex *tex)
 		return;
 	}
 	tex_id->tag |= LIB_TAG_DOIT;
-	/* texture itself */
+	/* Texture itself. */
 	build_animdata(tex_id);
-	/* texture's nodetree */
+	/* Texture's nodetree. */
 	build_nodetree(owner_node, tex->nodetree);
+	/* Special cases for different IDs which texture uses. */
+	if (tex->type == TEX_IMAGE) {
+		if (tex->ima != NULL) {
+			build_image(tex->ima);
+		}
+	}
+}
+
+void DepsgraphNodeBuilder::build_image(Image *image) {
+	ID *image_id = &image->id;
+	if (image_id->tag & LIB_TAG_DOIT) {
+		return;
+	}
+	image_id->tag |= LIB_TAG_DOIT;
+	/* Image ID node itself. */
+	add_id_node(image_id);
+	/* Placeholder so we can add relations and tag ID node for update. */
+	add_operation_node(image_id,
+	                   DEPSNODE_TYPE_PARAMETERS,
+	                   DEPSOP_TYPE_EXEC,
+	                   NULL,
+	                   DEG_OPCODE_PLACEHOLDER,
+	                   "Image Eval");
 }
 
 void DepsgraphNodeBuilder::build_compositor(Scene *scene)
diff --git a/source/blender/depsgraph/intern/builder/deg_builder_nodes.h b/source/blender/depsgraph/intern/builder/deg_builder_nodes.h
index f378f076804..09d264c4b59 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_nodes.h
+++ b/source/blender/depsgraph/intern/builder/deg_builder_nodes.h
@@ -38,6 +38,7 @@ struct bGPdata;
 struct ListBase;
 struct GHash;
 struct ID;
+struct Image;
 struct FCurve;
 struct Group;
 struct Key;
@@ -142,6 +143,7 @@ struct DepsgraphNodeBuilder {
 	void build_material(DepsNode *owner_node, Material *ma);
 	void build_texture(DepsNode *owner_node, Tex *tex);
 	void build_texture_stack(DepsNode *owner_node, MTex **texture_stack);
+	void build_image(Image *image);
 	void build_world(World *world);
 	void build_compositor(Scene *scene);
 	void build_gpencil(bGPdata *gpd);