Node Editor: Link Drag Search Menu

This commit adds a search menu when links are dragged above empty
space. When releasing the drag, a menu displays all compatible
sockets with the source link. The "main" sockets (usually the first)
are weighted above other sockets in the search, so they appear first
when you type the name of the node.

A few special operators for creating a reroute or a group input node
are also added to the search.

Translation is started after choosing a node so it can be placed
quickly, since users would likely adjust the position after anyway.

A small "+" is displayed next to the cursor to give a hint about this.

Further improvements are possible after this first iteration:
 - Support custom node trees.
 - Better drawing of items in the search menu.
 - Potential tweaks to filtering of items, depending on user feedback.

Thanks to Juanfran Matheu for developing an initial patch.

Differential Revision: https://developer.blender.org/D8286

1 files changed, 137 insertions, 18 deletions

diff --git a/source/blender/editors/space_node/node_relationships.cc b/source/blender/editors/space_node/node_relationships.cc
index ce07496068d..90b53258d5e 100644
--- a/source/blender/editors/space_node/node_relationships.cc
+++ b/source/blender/editors/space_node/node_relationships.cc
@@ -39,6 +39,7 @@
 #include "ED_node.h" /* own include */
 #include "ED_render.h"
 #include "ED_screen.h"
+#include "ED_space_api.h"
 #include "ED_spreadsheet.h"
 #include "ED_util.h"
 
@@ -50,6 +51,9 @@
 #include "WM_api.h"
 #include "WM_types.h"
 
+#include "GPU_state.h"
+
+#include "UI_interface_icons.h"
 #include "UI_resources.h"
 #include "UI_view2d.h"
 
@@ -57,11 +61,15 @@
 
 #include "NOD_node_declaration.hh"
 #include "NOD_node_tree_ref.hh"
+#include "NOD_socket_declarations.hh"
+#include "NOD_socket_declarations_geometry.hh"
 
 #include "node_intern.hh" /* own include */
 
 using namespace blender::nodes::node_tree_ref_types;
 using blender::float2;
+using blender::StringRef;
+using blender::StringRefNull;
 using blender::Vector;
 
 /* -------------------------------------------------------------------- */
@@ -890,6 +898,83 @@ void NODE_OT_link_viewer(wmOperatorType *ot)
 /** \name Add Link Operator
  * \{ */
 
+/**
+ * Check if any of the dragged links are connected to a socket on the side that they are dragged
+ * from.
+ */
+static bool dragged_links_are_detached(const bNodeLinkDrag &nldrag)
+{
+  if (nldrag.in_out == SOCK_OUT) {
+    for (const bNodeLink *link : nldrag.links) {
+      if (link->tonode && link->tosock) {
+        return false;
+      }
+    }
+  }
+  else {
+    for (const bNodeLink *link : nldrag.links) {
+      if (link->fromnode && link->fromsock) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+static bool should_create_drag_link_search_menu(const bNodeTree &node_tree,
+                                                const bNodeLinkDrag &nldrag)
+{
+  /* Custom node trees aren't supported yet. */
+  if (node_tree.type == NTREE_CUSTOM) {
+    return false;
+  }
+  /* Only create the search menu when the drag has not already connected the links to a socket. */
+  if (!dragged_links_are_detached(nldrag)) {
+    return false;
+  }
+  /* Don't create the search menu if the drag is disconnecting a link from an input node. */
+  if (nldrag.start_socket->in_out == SOCK_IN && nldrag.start_link_count > 0) {
+    return false;
+  }
+  /* Don't allow a drag from the "new socket" of a group input node. Handling these
+   * properly in node callbacks increases the complexity too much for now. */
+  if (ELEM(nldrag.start_node->type, NODE_GROUP_INPUT, NODE_GROUP_OUTPUT)) {
+    if (nldrag.start_socket->type == SOCK_CUSTOM) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static void draw_draglink_tooltip(const bContext *UNUSED(C), ARegion *UNUSED(region), void *arg)
+{
+  bNodeLinkDrag *nldrag = static_cast<bNodeLinkDrag *>(arg);
+
+  const uchar text_col[4] = {255, 255, 255, 255};
+  const int padding = 4 * UI_DPI_FAC;
+  const float x = nldrag->in_out == SOCK_IN ? nldrag->cursor[0] - 3.3f * padding :
+                                              nldrag->cursor[0];
+  const float y = nldrag->cursor[1] - 2.0f * UI_DPI_FAC;
+
+  UI_icon_draw_ex(x, y, ICON_ADD, U.inv_dpi_fac, 1.0f, 0.0f, text_col, false);
+}
+
+static void draw_draglink_tooltip_activate(const ARegion &region, bNodeLinkDrag &nldrag)
+{
+  if (nldrag.draw_handle == nullptr) {
+    nldrag.draw_handle = ED_region_draw_cb_activate(
+        region.type, draw_draglink_tooltip, &nldrag, REGION_DRAW_POST_PIXEL);
+  }
+}
+
+static void draw_draglink_tooltip_deactivate(const ARegion &region, bNodeLinkDrag &nldrag)
+{
+  if (nldrag.draw_handle) {
+    ED_region_draw_cb_exit(region.type, nldrag.draw_handle);
+    nldrag.draw_handle = nullptr;
+  }
+}
+
 static void node_link_update_header(bContext *C, bNodeLinkDrag *UNUSED(nldrag))
 {
   char header[UI_MAX_DRAW_STR];
@@ -952,12 +1037,11 @@ static void node_remove_extra_links(SpaceNode &snode, bNodeLink &link)
 static void node_link_exit(bContext &C, wmOperator &op, const bool apply_links)
 {
   Main *bmain = CTX_data_main(&C);
+  ARegion &region = *CTX_wm_region(&C);
   SpaceNode &snode = *CTX_wm_space_node(&C);
   bNodeTree &ntree = *snode.edittree;
   bNodeLinkDrag *nldrag = (bNodeLinkDrag *)op.customdata;
   bool do_tag_update = false;
-  /* View will be reset if no links connect. */
-  bool reset_view = true;
 
   /* avoid updates while applying links */
   ntree.is_updating = true;
@@ -995,8 +1079,6 @@ static void node_link_exit(bContext &C, wmOperator &op, const bool apply_links)
       if (link->tonode) {
         do_tag_update |= (do_tag_update || node_connected_to_output(*bmain, ntree, *link->tonode));
       }
-
-      reset_view = false;
     }
     else {
       nodeRemLink(&ntree, link);
@@ -1010,9 +1092,12 @@ static void node_link_exit(bContext &C, wmOperator &op, const bool apply_links)
     snode_dag_update(C, snode);
   }
 
-  if (reset_view) {
-    UI_view2d_edge_pan_cancel(&C, &nldrag->pan_data);
-  }
+  /* Ensure draglink tooltip is disabled. */
+  draw_draglink_tooltip_deactivate(*CTX_wm_region(&C), *nldrag);
+
+  ED_workspace_status_text(&C, nullptr);
+  ED_region_tag_redraw(&region);
+  clear_picking_highlight(&snode.edittree->links);
 
   snode.runtime->linkdrag.reset();
 }
@@ -1099,12 +1184,15 @@ static void node_link_find_socket(bContext &C, wmOperator &op, const float2 &cur
 static int node_link_modal(bContext *C, wmOperator *op, const wmEvent *event)
 {
   bNodeLinkDrag *nldrag = (bNodeLinkDrag *)op->customdata;
+  SpaceNode &snode = *CTX_wm_space_node(C);
   ARegion *region = CTX_wm_region(C);
 
   UI_view2d_edge_pan_apply_event(C, &nldrag->pan_data, event);
 
   float2 cursor;
   UI_view2d_region_to_view(&region->v2d, event->mval[0], event->mval[1], &cursor.x, &cursor.y);
+  nldrag->cursor[0] = event->mval[0];
+  nldrag->cursor[1] = event->mval[1];
 
   switch (event->type) {
     case MOUSEMOVE:
@@ -1117,22 +1205,46 @@ static int node_link_modal(bContext *C, wmOperator *op, const wmEvent *event)
         node_link_update_header(C, nldrag);
         ED_region_tag_redraw(region);
       }
-      break;
 
+      if (should_create_drag_link_search_menu(*snode.edittree, *nldrag)) {
+        draw_draglink_tooltip_activate(*region, *nldrag);
+      }
+      else {
+        draw_draglink_tooltip_deactivate(*region, *nldrag);
+      }
+      break;
     case LEFTMOUSE:
+      if (event->val == KM_RELEASE) {
+        /* Add a search menu for compatible sockets if the drag released on empty space. */
+        if (should_create_drag_link_search_menu(*snode.edittree, *nldrag)) {
+          bNodeLink &link = *nldrag->links.first();
+          if (nldrag->in_out == SOCK_OUT) {
+            blender::ed::space_node::invoke_node_link_drag_add_menu(
+                *C, *link.fromnode, *link.fromsock, cursor);
+          }
+          else {
+            blender::ed::space_node::invoke_node_link_drag_add_menu(
+                *C, *link.tonode, *link.tosock, cursor);
+          }
+        }
+
+        /* Finish link. */
+        node_link_exit(*C, *op, true);
+        return OPERATOR_FINISHED;
+      }
+      break;
     case RIGHTMOUSE:
     case MIDDLEMOUSE: {
       if (event->val == KM_RELEASE) {
         node_link_exit(*C, *op, true);
-
-        ED_workspace_status_text(C, nullptr);
-        ED_region_tag_redraw(region);
-        SpaceNode &snode = *CTX_wm_space_node(C);
-        clear_picking_highlight(&snode.edittree->links);
         return OPERATOR_FINISHED;
       }
       break;
     }
+    case EVT_ESCKEY: {
+      node_link_exit(*C, *op, true);
+      return OPERATOR_FINISHED;
+    }
   }
 
   return OPERATOR_RUNNING_MODAL;
@@ -1148,10 +1260,11 @@ static std::unique_ptr<bNodeLinkDrag> node_link_init(Main &bmain,
   bNodeSocket *sock;
   if (node_find_indicated_socket(snode, &node, &sock, cursor, SOCK_OUT)) {
     std::unique_ptr<bNodeLinkDrag> nldrag = std::make_unique<bNodeLinkDrag>();
-
-    const int num_links = nodeCountSocketLinks(snode.edittree, sock);
+    nldrag->start_node = node;
+    nldrag->start_socket = sock;
+    nldrag->start_link_count = nodeCountSocketLinks(snode.edittree, sock);
     int link_limit = nodeSocketLinkLimit(sock);
-    if (num_links > 0 && (num_links >= link_limit || detach)) {
+    if (nldrag->start_link_count > 0 && (nldrag->start_link_count >= link_limit || detach)) {
       /* dragged links are fixed on input side */
       nldrag->in_out = SOCK_IN;
       /* detach current links and store them in the operator data */
@@ -1192,9 +1305,11 @@ static std::unique_ptr<bNodeLinkDrag> node_link_init(Main &bmain,
   if (node_find_indicated_socket(snode, &node, &sock, cursor, SOCK_IN)) {
     std::unique_ptr<bNodeLinkDrag> nldrag = std::make_unique<bNodeLinkDrag>();
     nldrag->last_node_hovered_while_dragging_a_link = node;
+    nldrag->start_node = node;
+    nldrag->start_socket = sock;
 
-    const int num_links = nodeCountSocketLinks(snode.edittree, sock);
-    if (num_links > 0) {
+    nldrag->start_link_count = nodeCountSocketLinks(snode.edittree, sock);
+    if (nldrag->start_link_count > 0) {
       /* dragged links are fixed on output side */
       nldrag->in_out = SOCK_OUT;
       /* detach current links and store them in the operator data */
@@ -1260,6 +1375,10 @@ static int node_link_invoke(bContext *C, wmOperator *op, const wmEvent *event)
   if (nldrag) {
     UI_view2d_edge_pan_operator_init(C, &nldrag->pan_data, op);
 
+    /* Add "+" icon when the link is dragged in empty space. */
+    if (should_create_drag_link_search_menu(*snode.edittree, *nldrag)) {
+      draw_draglink_tooltip_activate(*CTX_wm_region(C), *nldrag);
+    }
     snode.runtime->linkdrag = std::move(nldrag);
     op->customdata = snode.runtime->linkdrag.get();