scripts/startup/bl_ui/space_node.py

@@ -865,6 +865,7 @@ class NODE_PT_overlay(Panel):
 
         col = layout.column()
         col.prop(overlay, "show_wire_color", text="Wire Colors")
+        col.prop(overlay, "show_reroute_auto_labels", text="Reroute Auto Labels")
 
         col.separator()
 

source/blender/blenloader/intern/versioning_400.cc

@@ -4049,6 +4049,19 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
     }
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 402, 53)) {
+    LISTBASE_FOREACH (bScreen *, screen, &bmain->screens) {
+      LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+        LISTBASE_FOREACH (SpaceLink *, sl, &area->spacedata) {
+          if (sl->spacetype == SPACE_NODE) {
+            SpaceNode *snode = reinterpret_cast<SpaceNode *>(sl);
+            snode->overlay.flag |= SN_OVERLAY_SHOW_REROUTE_AUTO_LABELS;
+          }
+        }
+      }
+    }
+  }
+
   /**
    * Always bump subversion in BKE_blender_version.h when adding versioning
    * code here, and wrap it inside a MAIN_VERSION_FILE_ATLEAST check.

source/blender/editors/space_node/node_draw.cc

@@ -131,6 +131,11 @@ struct TreeDrawContext {
 
   blender::Map<bNodeInstanceKey, blender::timeit::Nanoseconds>
       *compositor_per_node_execution_time = nullptr;
+
+  /**
+   * Label for reroute nodes that is derived from upstream reroute nodes.
+   */
+  blender::Map<const bNode *, blender::StringRefNull> reroute_auto_labels;
 };
 
 float ED_node_grid_size()
@@ -2060,6 +2065,15 @@ void node_socket_draw(bNodeSocket *sock, const rcti *rect, const float color[4],
   GPU_blend(state);
 }
 
+/** Some elements of the node UI are hidden, when they get too small. */
+#define NODE_TREE_SCALE_SMALL 0.2f
+
+/** The node tree scales both with the view and with the UI. */
+static float node_tree_view_scale(const SpaceNode &snode)
+{
+  return (1.0f / snode.runtime->aspect) * UI_SCALE_FAC;
+}
+
 static void node_draw_preview_background(rctf *rect)
 {
   GPUVertFormat *format = immVertexFormat();
@@ -3625,11 +3639,8 @@ static void node_draw_basis(const bContext &C,
     UI_draw_roundbox_4fv(&rect, false, BASIS_RAD + outline_width, color_outline);
   }
 
-  float scale;
-  UI_view2d_scale_get(&v2d, &scale, nullptr);
-
   /* Skip slow socket drawing if zoom is small. */
-  if (scale > 0.2f) {
+  if (node_tree_view_scale(snode) > NODE_TREE_SCALE_SMALL) {
     node_draw_sockets(v2d, C, ntree, node, block, true, false);
   }
 
@@ -4151,8 +4162,108 @@ static void frame_node_draw(const bContext &C,
   UI_block_draw(&C, &block);
 }
 
-static void reroute_node_draw(
-    const bContext &C, ARegion &region, bNodeTree &ntree, const bNode &node, uiBlock &block)
+/**
+ * Returns the reroute node linked to the input of the given reroute, if there is one.
+ */
+static const bNode *reroute_node_get_linked_reroute(const bNode &reroute)
+{
+  BLI_assert(reroute.is_reroute());
+
+  const bNodeSocket *input_socket = reroute.input_sockets().first();
+  if (input_socket->directly_linked_links().is_empty()) {
+    return nullptr;
+  }
+  const bNodeLink *input_link = input_socket->directly_linked_links().first();
+  const bNode *from_node = input_link->fromnode;
+  return from_node->is_reroute() ? from_node : nullptr;
+}
+
+/**
+ * The auto label overlay displays a label on reroute nodes based on the user-defined label of a
+ * linked reroute upstream.
+ */
+static StringRefNull reroute_node_get_auto_label(TreeDrawContext &tree_draw_ctx,
+                                                 const bNode &src_reroute)
+{
+  BLI_assert(src_reroute.is_reroute());
+
+  if (src_reroute.label[0] != '\0') {
+    return StringRefNull(src_reroute.label);
+  }
+
+  Map<const bNode *, StringRefNull> &reroute_auto_labels = tree_draw_ctx.reroute_auto_labels;
+
+  StringRefNull label;
+  Vector<const bNode *> reroute_path;
+
+  /* Traverse reroute path backwards until label, non-reroute node or link-cycle is found. */
+  for (const bNode *reroute = &src_reroute; reroute;
+       reroute = reroute_node_get_linked_reroute(*reroute))
+  {
+    reroute_path.append(reroute);
+    if (const StringRefNull *label_ptr = reroute_auto_labels.lookup_ptr(reroute)) {
+      label = *label_ptr;
+      break;
+    }
+    if (reroute->label[0] != '\0') {
+      label = reroute->label;
+      break;
+    }
+    /* This makes sure that the loop eventually ends even if there are link-cycles. */
+    reroute_auto_labels.add(reroute, "");
+  }
+
+  /* Remember the label for each node on the path to avoid recomputing it. */
+  for (const bNode *reroute : reroute_path) {
+    reroute_auto_labels.add_overwrite(reroute, label);
+  }
+
+  return label;
+}
+
+static void reroute_node_draw_label(TreeDrawContext &tree_draw_ctx,
+                                    const SpaceNode &snode,
+                                    const bNode &node,
+                                    uiBlock &block)
+{
+  const bool has_label = node.label[0] != '\0';
+  const bool use_auto_label = !has_label && (snode.overlay.flag & SN_OVERLAY_SHOW_OVERLAYS) &&
+                              (snode.overlay.flag & SN_OVERLAY_SHOW_REROUTE_AUTO_LABELS);
+
+  if (!has_label && !use_auto_label) {
+    return;
+  }
+
+  /* Don't show the automatic label, when being zoomed out. */
+  if (!has_label && node_tree_view_scale(snode) < NODE_TREE_SCALE_SMALL) {
+    return;
+  }
+
+  char showname[128];
+  STRNCPY(showname,
+          has_label ? node.label : reroute_node_get_auto_label(tree_draw_ctx, node).c_str());
+
+  const short width = 512;
+  const int x = BLI_rctf_cent_x(&node.runtime->totr) - (width / 2);
+  const int y = node.runtime->totr.ymax;
+
+  uiBut *label_but = uiDefBut(
+      &block, UI_BTYPE_LABEL, 0, showname, x, y, width, short(NODE_DY), nullptr, 0, 0, nullptr);
+
+  UI_but_drawflag_disable(label_but, UI_BUT_TEXT_LEFT);
+
+  if (use_auto_label && !(node.flag & NODE_SELECT)) {
+    UI_but_flag_enable(label_but, UI_BUT_INACTIVE);
+  }
+}
+
+static void reroute_node_draw(const bContext &C,
+                              TreeDrawContext &tree_draw_ctx,
+                              ARegion &region,
+                              const SpaceNode &snode,
+                              bNodeTree &ntree,
+                              const bNode &node,
+                              uiBlock &block)
 {
   /* Skip if out of view. */
   const rctf &rct = node.runtime->totr;
@@ -4163,19 +4274,7 @@ static void reroute_node_draw(
     return;
   }
 
-  if (node.label[0] != '\0') {
-    /* Draw title (node label). */
-    char showname[128]; /* 128 used below */
-    STRNCPY(showname, node.label);
-    const short width = 512;
-    const int x = BLI_rctf_cent_x(&node.runtime->totr) - (width / 2);
-    const int y = node.runtime->totr.ymax;
-
-    uiBut *label_but = uiDefBut(
-        &block, UI_BTYPE_LABEL, 0, showname, x, y, width, short(NODE_DY), nullptr, 0, 0, nullptr);
-
-    UI_but_drawflag_disable(label_but, UI_BUT_TEXT_LEFT);
-  }
+  reroute_node_draw_label(tree_draw_ctx, snode, node, block);
 
   /* Only draw input socket as they all are placed on the same position highlight
    * if node itself is selected, since we don't display the node body separately. */
@@ -4198,7 +4297,7 @@ static void node_draw(const bContext &C,
     frame_node_draw(C, tree_draw_ctx, region, snode, ntree, node, block);
   }
   else if (node.is_reroute()) {
-    reroute_node_draw(C, region, ntree, node, block);
+    reroute_node_draw(C, tree_draw_ctx, region, snode, ntree, node, block);
   }
   else {
     const View2D &v2d = region.v2d;

source/blender/makesdna/DNA_space_types.h

@@ -1555,6 +1555,11 @@ typedef enum eSpaceNodeOverlay_Flag {
   SN_OVERLAY_SHOW_PATH = (1 << 4),
   SN_OVERLAY_SHOW_NAMED_ATTRIBUTES = (1 << 5),
   SN_OVERLAY_SHOW_PREVIEWS = (1 << 6),
+  /**
+   * Display an automatic label on reroute nodes based on the user-defined labels
+   * of connected reroute nodes.
+   */
+  SN_OVERLAY_SHOW_REROUTE_AUTO_LABELS = (1 << 7),
 } eSpaceNodeOverlay_Flag;
 
 typedef enum eSpaceNodeOverlay_preview_shape {

source/blender/makesrna/intern/rna_space.cc

@@ -7580,6 +7580,15 @@ static void rna_def_space_node_overlay(BlenderRNA *brna)
       prop, "Show Wire Colors", "Color node links based on their connected sockets");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_NODE, nullptr);
 
+  prop = RNA_def_property(srna, "show_reroute_auto_labels", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(
+      prop, nullptr, "overlay.flag", SN_OVERLAY_SHOW_REROUTE_AUTO_LABELS);
+  RNA_def_property_boolean_default(prop, false);
+  RNA_def_property_ui_text(prop,
+                           "Show Reroute Auto Labels",
+                           "Label reroute nodes based on the label of connected reroute nodes");
+  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_NODE, nullptr);
+
   prop = RNA_def_property(srna, "show_timing", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, nullptr, "overlay.flag", SN_OVERLAY_SHOW_TIMINGS);
   RNA_def_property_boolean_default(prop, false);