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, 291 insertions, 0 deletions

diff --git a/source/blender/editors/space_node/link_drag_search.cc b/source/blender/editors/space_node/link_drag_search.cc
new file mode 100644
index 00000000000..e1ba36e81c0
--- /dev/null
+++ b/source/blender/editors/space_node/link_drag_search.cc
@@ -0,0 +1,291 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "BLI_listbase.h"
+#include "BLI_string_search.h"
+
+#include "DNA_space_types.h"
+
+#include "BKE_context.h"
+
+#include "NOD_socket_search_link.hh"
+
+#include "BLT_translation.h"
+
+#include "RNA_access.h"
+
+#include "WM_api.h"
+
+#include "node_intern.hh"
+
+using blender::nodes::SocketLinkOperation;
+
+namespace blender::ed::space_node {
+
+struct LinkDragSearchStorage {
+  bNode &from_node;
+  bNodeSocket &from_socket;
+  float2 cursor;
+  Vector<SocketLinkOperation> search_link_ops;
+  char search[256];
+
+  eNodeSocketInOut in_out() const
+  {
+    return static_cast<eNodeSocketInOut>(from_socket.in_out);
+  }
+};
+
+static void add_reroute_node_fn(nodes::LinkSearchOpParams &params)
+{
+  bNode &reroute = params.add_node("NodeReroute");
+  if (params.socket.in_out == SOCK_IN) {
+    nodeAddLink(&params.node_tree,
+                &reroute,
+                static_cast<bNodeSocket *>(reroute.outputs.first),
+                &params.node,
+                &params.socket);
+  }
+  else {
+    nodeAddLink(&params.node_tree,
+                &params.node,
+                &params.socket,
+                &reroute,
+                static_cast<bNodeSocket *>(reroute.inputs.first));
+  }
+}
+
+static void add_group_input_node_fn(nodes::LinkSearchOpParams &params)
+{
+  /* Add a group input based on the connected socket, and add a new group input node. */
+  bNodeSocket *interface_socket = ntreeAddSocketInterfaceFromSocket(
+      &params.node_tree, &params.node, &params.socket);
+  const int group_input_index = BLI_findindex(&params.node_tree.inputs, interface_socket);
+
+  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);
+
+  /* Hide the new input in all other group input nodes, to avoid making them taller. */
+  LISTBASE_FOREACH (bNode *, node, &params.node_tree.nodes) {
+    if (node->type == NODE_GROUP_INPUT) {
+      bNodeSocket *new_group_input_socket = (bNodeSocket *)BLI_findlink(&node->outputs,
+                                                                        group_input_index);
+      new_group_input_socket->flag |= SOCK_HIDDEN;
+    }
+  }
+
+  /* Hide all existing inputs in the new group input node, to only display the new one. */
+  LISTBASE_FOREACH (bNodeSocket *, socket, &group_input.outputs) {
+    socket->flag |= SOCK_HIDDEN;
+  }
+
+  bNodeSocket *socket = (bNodeSocket *)BLI_findlink(&group_input.outputs, group_input_index);
+  if (socket == nullptr) {
+    /* Adding sockets can fail in some cases. There's no good reason not to be safe here. */
+    return;
+  }
+  /* Unhide the socket for the new input in the new node and make a connection to it. */
+  socket->flag &= ~SOCK_HIDDEN;
+  nodeAddLink(&params.node_tree, &group_input, socket, &params.node, &params.socket);
+}
+
+/**
+ * Call the callback to gather compatible socket connections for all node types, and the operations
+ * that will actually make the connections. Also add some custom operations like connecting a group
+ * output node.
+ */
+static void gather_socket_link_operations(bNodeTree &node_tree,
+                                          const bNodeSocket &socket,
+                                          Vector<SocketLinkOperation> &search_link_ops)
+{
+  NODE_TYPES_BEGIN (node_type) {
+    if (StringRef(node_type->idname).find("Legacy") != StringRef::not_found) {
+      continue;
+    }
+    const char *disabled_hint;
+    if (!(node_type->poll && node_type->poll(node_type, &node_tree, &disabled_hint))) {
+      continue;
+    }
+
+    if (node_type->gather_link_search_ops) {
+      nodes::GatherLinkSearchOpParams params{*node_type, node_tree, socket, search_link_ops};
+      node_type->gather_link_search_ops(params);
+    }
+  }
+  NODE_TYPES_END;
+
+  search_link_ops.append({IFACE_("Reroute"), add_reroute_node_fn});
+
+  const bool is_node_group = !(node_tree.id.flag & LIB_EMBEDDED_DATA);
+
+  if (is_node_group && socket.in_out == SOCK_IN) {
+    search_link_ops.append({IFACE_("Group Input"), add_group_input_node_fn});
+  }
+}
+
+static void link_drag_search_update_fn(const bContext *UNUSED(C),
+                                       void *arg,
+                                       const char *str,
+                                       uiSearchItems *items,
+                                       const bool is_first)
+{
+  LinkDragSearchStorage &storage = *static_cast<LinkDragSearchStorage *>(arg);
+
+  StringSearch *search = BLI_string_search_new();
+
+  for (SocketLinkOperation &op : storage.search_link_ops) {
+    BLI_string_search_add(search, op.name.c_str(), &op, op.weight);
+  }
+
+  /* Don't filter when the menu is first opened, but still run the search
+   * so the items are in the same order they will appear in while searching. */
+  const char *string = is_first ? "" : str;
+  SocketLinkOperation **filtered_items;
+  const int filtered_amount = BLI_string_search_query(search, string, (void ***)&filtered_items);
+
+  for (const int i : IndexRange(filtered_amount)) {
+    SocketLinkOperation &item = *filtered_items[i];
+    if (!UI_search_item_add(items, item.name.c_str(), &item, ICON_NONE, 0, 0)) {
+      break;
+    }
+  }
+
+  MEM_freeN(filtered_items);
+  BLI_string_search_free(search);
+}
+
+static void link_drag_search_exec_fn(bContext *C, void *arg1, void *arg2)
+{
+  Main &bmain = *CTX_data_main(C);
+  SpaceNode &snode = *CTX_wm_space_node(C);
+  LinkDragSearchStorage &storage = *static_cast<LinkDragSearchStorage *>(arg1);
+  SocketLinkOperation *item = static_cast<SocketLinkOperation *>(arg2);
+  if (item == nullptr) {
+    return;
+  }
+
+  node_deselect_all(snode);
+
+  Vector<bNode *> new_nodes;
+  nodes::LinkSearchOpParams params{
+      *C, *snode.edittree, storage.from_node, storage.from_socket, new_nodes};
+  item->fn(params);
+  if (new_nodes.is_empty()) {
+    return;
+  }
+
+  /* For now, assume that only one node is created by the callback. */
+  BLI_assert(new_nodes.size() == 1);
+  bNode *new_node = new_nodes.first();
+
+  new_node->locx = storage.cursor.x / UI_DPI_FAC;
+  new_node->locy = storage.cursor.y / UI_DPI_FAC + 20 * UI_DPI_FAC;
+  if (storage.in_out() == SOCK_IN) {
+    new_node->locx -= new_node->width;
+  }
+
+  nodeSetSelected(new_node, true);
+  nodeSetActive(snode.edittree, new_node);
+
+  /* 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);
+
+  /* Start translation operator with the new node. */
+  wmOperatorType *ot = WM_operatortype_find("TRANSFORM_OT_translate", true);
+  BLI_assert(ot);
+  PointerRNA ptr;
+  WM_operator_properties_create_ptr(&ptr, ot);
+  RNA_boolean_set(&ptr, "view2d_edge_pan", true);
+  WM_operator_name_call_ptr(C, ot, WM_OP_INVOKE_DEFAULT, &ptr);
+  WM_operator_properties_free(&ptr);
+}
+
+static void link_drag_search_free_fn(void *arg)
+{
+  LinkDragSearchStorage *storage = static_cast<LinkDragSearchStorage *>(arg);
+  delete storage;
+}
+
+static uiBlock *create_search_popup_block(bContext *C, ARegion *region, void *arg_op)
+{
+  LinkDragSearchStorage &storage = *(LinkDragSearchStorage *)arg_op;
+
+  bNodeTree *node_tree = CTX_wm_space_node(C)->nodetree;
+  gather_socket_link_operations(*node_tree, storage.from_socket, storage.search_link_ops);
+
+  uiBlock *block = UI_block_begin(C, region, "_popup", UI_EMBOSS);
+  UI_block_flag_enable(block, UI_BLOCK_LOOP | UI_BLOCK_MOVEMOUSE_QUIT | UI_BLOCK_SEARCH_MENU);
+  UI_block_theme_style_set(block, UI_BLOCK_THEME_STYLE_POPUP);
+
+  uiBut *but = uiDefSearchBut(block,
+                              storage.search,
+                              0,
+                              ICON_VIEWZOOM,
+                              sizeof(storage.search),
+                              storage.in_out() == SOCK_OUT ? 10 : 10 - UI_searchbox_size_x(),
+                              10,
+                              UI_searchbox_size_x(),
+                              UI_UNIT_Y,
+                              0,
+                              0,
+                              "");
+  UI_but_func_search_set_sep_string(but, UI_MENU_ARROW_SEP);
+  UI_but_func_search_set(but,
+                         nullptr,
+                         link_drag_search_update_fn,
+                         &storage,
+                         false,
+                         link_drag_search_free_fn,
+                         link_drag_search_exec_fn,
+                         nullptr);
+  UI_but_flag_enable(but, UI_BUT_ACTIVATE_ON_INIT);
+
+  /* Fake button to hold space for the search items. */
+  uiDefBut(block,
+           UI_BTYPE_LABEL,
+           0,
+           "",
+           storage.in_out() == SOCK_OUT ? 10 : 10 - UI_searchbox_size_x(),
+           10 - UI_searchbox_size_y(),
+           UI_searchbox_size_x(),
+           UI_searchbox_size_y(),
+           nullptr,
+           0,
+           0,
+           0,
+           0,
+           nullptr);
+
+  const int offset[2] = {0, -UI_UNIT_Y};
+  UI_block_bounds_set_popup(block, 0.3f * U.widget_unit, offset);
+  return block;
+}
+
+void invoke_node_link_drag_add_menu(bContext &C,
+                                    bNode &node,
+                                    bNodeSocket &socket,
+                                    const float2 &cursor)
+{
+  LinkDragSearchStorage *storage = new LinkDragSearchStorage{node, socket, cursor};
+  /* Use the "_ex" variant with `can_refresh` false to avoid a double free when closing Blender. */
+  UI_popup_block_invoke_ex(&C, create_search_popup_block, storage, nullptr, false);
+}
+
+}  // namespace blender::ed::space_node
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