3 files changed, 73 insertions, 2 deletions

diff --git a/source/blender/depsgraph/DEG_depsgraph_build.h b/source/blender/depsgraph/DEG_depsgraph_build.h
index 15abc0c0a64..effcece6e00 100644
--- a/source/blender/depsgraph/DEG_depsgraph_build.h
+++ b/source/blender/depsgraph/DEG_depsgraph_build.h
@@ -33,6 +33,7 @@ struct Depsgraph;
 
 /* ------------------------------------------------ */
 
+struct bNodeTree;
 struct CacheFile;
 struct Collection;
 struct CustomData_MeshMasks;
@@ -65,6 +66,17 @@ void DEG_graph_build_for_render_pipeline(struct Depsgraph *graph,
                                          struct Scene *scene,
                                          struct ViewLayer *view_layer);
 
+/* Builds minimal dependency graph for compositor preview.
+ *
+ * Note that compositor editor might have pinned node tree, which is different from scene's node
+ * tree.
+ */
+void DEG_graph_build_for_compositor_preview(struct Depsgraph *graph,
+                                            struct Main *bmain,
+                                            struct Scene *scene,
+                                            struct ViewLayer *view_layer,
+                                            struct bNodeTree *nodetree);
+
 /* Tag relations from the given graph for update. */
 void DEG_graph_tag_relations_update(struct Depsgraph *graph);
 
diff --git a/source/blender/depsgraph/intern/depsgraph_build.cc b/source/blender/depsgraph/intern/depsgraph_build.cc
index 138b23888b4..cf1ebccc6c6 100644
--- a/source/blender/depsgraph/intern/depsgraph_build.cc
+++ b/source/blender/depsgraph/intern/depsgraph_build.cc
@@ -315,6 +315,42 @@ void DEG_graph_build_for_render_pipeline(Depsgraph *graph,
   }
 }
 
+void DEG_graph_build_for_compositor_preview(Depsgraph *graph,
+                                            Main *bmain,
+                                            Scene *scene,
+                                            struct ViewLayer * /*view_layer*/,
+                                            bNodeTree *nodetree)
+{
+  double start_time = 0.0;
+  if (G.debug & (G_DEBUG_DEPSGRAPH_BUILD | G_DEBUG_DEPSGRAPH_TIME)) {
+    start_time = PIL_check_seconds_timer();
+  }
+  DEG::Depsgraph *deg_graph = reinterpret_cast<DEG::Depsgraph *>(graph);
+  /* Perform sanity checks. */
+  BLI_assert(deg_graph->scene == scene);
+  deg_graph->is_render_pipeline_depsgraph = true;
+  DEG::DepsgraphBuilderCache builder_cache;
+  /* Generate all the nodes in the graph first */
+  DEG::DepsgraphNodeBuilder node_builder(bmain, deg_graph, &builder_cache);
+  node_builder.begin_build();
+  node_builder.build_scene_render(scene);
+  node_builder.build_nodetree(nodetree);
+  node_builder.end_build();
+  /* Hook up relationships between operations - to determine evaluation
+   * order. */
+  DEG::DepsgraphRelationBuilder relation_builder(bmain, deg_graph, &builder_cache);
+  relation_builder.begin_build();
+  relation_builder.build_scene_render(scene);
+  relation_builder.build_nodetree(nodetree);
+  relation_builder.build_copy_on_write_relations();
+  /* Finalize building. */
+  graph_build_finalize_common(deg_graph, bmain);
+  /* Finish statistics. */
+  if (G.debug & (G_DEBUG_DEPSGRAPH_BUILD | G_DEBUG_DEPSGRAPH_TIME)) {
+    printf("Depsgraph built in %f seconds.\n", PIL_check_seconds_timer() - start_time);
+  }
+}
+
 /* Tag graph relations for update. */
 void DEG_graph_tag_relations_update(Depsgraph *graph)
 {
diff --git a/source/blender/editors/space_node/node_edit.c b/source/blender/editors/space_node/node_edit.c
index d54a30047e6..7a6e37bfd4d 100644
--- a/source/blender/editors/space_node/node_edit.c
+++ b/source/blender/editors/space_node/node_edit.c
@@ -42,6 +42,8 @@
 #include "BKE_scene.h"
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_query.h"
 
 #include "RE_engine.h"
 #include "RE_pipeline.h"
@@ -79,14 +81,19 @@ enum {
 };
 
 typedef struct CompoJob {
+  /* Input parameters. */
   Main *bmain;
   Scene *scene;
+  ViewLayer *view_layer;
   bNodeTree *ntree;
+  int recalc_flags;
+  /* Evaluated state/ */
+  Depsgraph *compositor_depsgraph;
   bNodeTree *localtree;
+  /* Jon system integration. */
   const short *stop;
   short *do_update;
   float *progress;
-  int recalc_flags;
 } CompoJob;
 
 static void compo_tag_output_nodes(bNodeTree *nodetree, int recalc_flags)
@@ -182,6 +189,9 @@ static void compo_freejob(void *cjv)
   if (cj->localtree) {
     ntreeLocalMerge(cj->bmain, cj->localtree, cj->ntree);
   }
+  if (cj->compositor_depsgraph != NULL) {
+    DEG_graph_free(cj->compositor_depsgraph);
+  }
   MEM_freeN(cj);
 }
 
@@ -190,8 +200,19 @@ static void compo_freejob(void *cjv)
 static void compo_initjob(void *cjv)
 {
   CompoJob *cj = cjv;
+  Main *bmain = cj->bmain;
+  Scene *scene = cj->scene;
+  ViewLayer *view_layer = cj->view_layer;
+
+  cj->compositor_depsgraph = DEG_graph_new(scene, view_layer, DAG_EVAL_RENDER);
+  DEG_graph_build_for_compositor_preview(
+      cj->compositor_depsgraph, bmain, scene, view_layer, cj->ntree);
+  DEG_evaluate_on_framechange(bmain, cj->compositor_depsgraph, CFRA);
+
+  bNodeTree *ntree_eval = (bNodeTree *)DEG_get_evaluated_id(cj->compositor_depsgraph,
+                                                            &cj->ntree->id);
 
-  cj->localtree = ntreeLocalize(cj->ntree);
+  cj->localtree = ntreeLocalize(ntree_eval);
 
   if (cj->recalc_flags) {
     compo_tag_output_nodes(cj->localtree, cj->recalc_flags);
@@ -283,6 +304,7 @@ void ED_node_composite_job(const bContext *C, struct bNodeTree *nodetree, Scene
   CompoJob *cj;
   Main *bmain = CTX_data_main(C);
   Scene *scene = CTX_data_scene(C);
+  ViewLayer *view_layer = CTX_data_view_layer(C);
 
   /* to fix bug: [#32272] */
   if (G.is_rendering) {
@@ -307,6 +329,7 @@ void ED_node_composite_job(const bContext *C, struct bNodeTree *nodetree, Scene
   /* customdata for preview thread */
   cj->bmain = bmain;
   cj->scene = scene;
+  cj->view_layer = view_layer;
   cj->ntree = nodetree;
   cj->recalc_flags = compo_get_recalc_flags(C);