Nodes: refactor node tree update handling

Goals of this refactor:
* More unified approach to updating everything that needs to be updated
  after a change in a node tree.
* The updates should happen in the correct order and quadratic or worse
  algorithms should be avoided.
* Improve detection of changes to the output to avoid tagging the depsgraph
  when it's not necessary.
* Move towards a more declarative style of defining nodes by having a
  more centralized update procedure.

The refactor consists of two main parts:
* Node tree tagging and update refactor.
  * Generally, when changes are done to a node tree, it is tagged dirty
    until a global update function is called that updates everything in
    the correct order.
  * The tagging is more fine-grained compared to before, to allow for more
    precise depsgraph update tagging.
* Depsgraph changes.
  * The shading specific depsgraph node for node trees as been removed.
  * Instead, there is a new `NTREE_OUTPUT` depsgrap node, which is only
    tagged when the output of the node tree changed (e.g. the Group Output
    or Material Output node).
  * The copy-on-write relation from node trees to the data block they are
    embedded in is now non-flushing. This avoids e.g. triggering a material
    update after the shader node tree changed in unrelated ways. Instead
    the material has a flushing relation to the new `NTREE_OUTPUT` node now.
  * The depsgraph no longer reports data block changes through to cycles
    through `Depsgraph.updates` when only the node tree changed in ways
    that do not affect the output.

Avoiding unnecessary updates seems to work well for geometry nodes and cycles.
The situation is a bit worse when there are drivers on the node tree, but that
could potentially be improved separately in the future.

Avoiding updates in eevee and the compositor is more tricky, but also less urgent.
* Eevee updates are triggered by calling `DRW_notify_view_update` in
  `ED_render_view3d_update` indirectly from `DEG_editors_update`.
* Compositor updates are triggered by `ED_node_composite_job` in `node_area_refresh`.
  This is triggered by calling `ED_area_tag_refresh` in `node_area_listener`.

Removing updates always has the risk of breaking some dependency that no
one was aware of. It's not unlikely that this will happen here as well. Adding
back missing updates should be quite a bit easier than getting rid of
unnecessary updates though.

Differential Revision: https://developer.blender.org/D13246

1 files changed, 5 insertions, 5 deletions

diff --git a/source/blender/editors/space_node/link_drag_search.cc b/source/blender/editors/space_node/link_drag_search.cc
index e1ba36e81c0..a2dd32b7cc6 100644
--- a/source/blender/editors/space_node/link_drag_search.cc
+++ b/source/blender/editors/space_node/link_drag_search.cc
@@ -29,6 +29,8 @@
 
 #include "WM_api.h"
 
+#include "ED_node.h"
+
 #include "node_intern.hh"
 
 using blender::nodes::SocketLinkOperation;
@@ -77,7 +79,7 @@ static void add_group_input_node_fn(nodes::LinkSearchOpParams &params)
   bNode &group_input = params.add_node("NodeGroupInput");
 
   /* This is necessary to create the new sockets in the other input nodes. */
-  ntreeUpdateTree(CTX_data_main(&params.C), &params.node_tree);
+  ED_node_tree_propagate_change(&params.C, CTX_data_main(&params.C), &params.node_tree);
 
   /* Hide the new input in all other group input nodes, to avoid making them taller. */
   LISTBASE_FOREACH (bNode *, node, &params.node_tree.nodes) {
@@ -203,9 +205,7 @@ static void link_drag_search_exec_fn(bContext *C, void *arg1, void *arg2)
 
   /* Ideally it would be possible to tag the node tree in some way so it updates only after the
    * translate operation is finished, but normally moving nodes around doesn't cause updates. */
-  ntreeUpdateTree(&bmain, snode.edittree);
-  snode_notify(*C, snode);
-  snode_dag_update(*C, snode);
+  ED_node_tree_propagate_change(C, &bmain, snode.edittree);
 
   /* Start translation operator with the new node. */
   wmOperatorType *ot = WM_operatortype_find("TRANSFORM_OT_translate", true);
@@ -288,4 +288,4 @@ void invoke_node_link_drag_add_menu(bContext &C,
   UI_popup_block_invoke_ex(&C, create_search_popup_block, storage, nullptr, false);
 }
 
-}  // namespace blender::ed::space_node
\ No newline at end of file
+}  // namespace blender::ed::space_node