Compositor: Implement shortcuts for Viewer nodes

Artists often want to quickly switch back and forth between two or more nodes while compositing.

This patch implements two operators `NODE_OT_viewer_shortcut_set` and `NODE_OT_viewer_shortcut_get` that allow users to map a viewer node to a shortcut. For example, pressing `cltr+1` while a node is selected, assigns that node to the shortcut `1`, creates a viewer node if it has none attached and sets that viewer node to active. Pressing `1` will set the active node with shortcut `1` to active.

Shortcuts are saved in DNA to preserve them after saving/loading blend files.

Limitations:
- Only compositor node tree is supported, because shading editor has no viewer node and geometry nodes viewer works differently.

Pull Request: https://projects.blender.org/blender/blender/pulls/123641

scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -2277,6 +2277,34 @@ def km_node_editor(params):
         ("wm.context_toggle", {"type": 'Z', "value": 'PRESS', "alt": True, "shift": True},
          {"properties": [("data_path", "space_data.overlay.show_overlays")]}),
         *_template_items_context_menu("NODE_MT_context_menu", params.context_menu_event),
+        # Viewer shortcuts.
+        ("node.viewer_shortcut_get", {"type": 'ONE', "value": 'PRESS'}, {"properties": [("viewer_index", 1)]}),
+        ("node.viewer_shortcut_set", {"type": 'ONE', "value": 'PRESS',
+         'ctrl': True}, {"properties": [("viewer_index", 1)]}),
+        ("node.viewer_shortcut_get", {"type": 'TWO', "value": 'PRESS'}, {"properties": [("viewer_index", 2)]}),
+        ("node.viewer_shortcut_set", {"type": 'TWO', "value": 'PRESS',
+         'ctrl': True}, {"properties": [("viewer_index", 2)]}),
+        ("node.viewer_shortcut_get", {"type": 'THREE', "value": 'PRESS'}, {"properties": [("viewer_index", 3)]}),
+        ("node.viewer_shortcut_set", {"type": 'THREE', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 3)]}),
+        ("node.viewer_shortcut_get", {"type": 'FOUR', "value": 'PRESS'}, {"properties": [("viewer_index", 4)]}),
+        ("node.viewer_shortcut_set", {"type": 'FOUR', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 4)]}),
+        ("node.viewer_shortcut_get", {"type": 'FIVE', "value": 'PRESS'}, {"properties": [("viewer_index", 5)]}),
+        ("node.viewer_shortcut_set", {"type": 'FIVE', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 5)]}),
+        ("node.viewer_shortcut_get", {"type": 'SIX', "value": 'PRESS'}, {"properties": [("viewer_index", 6)]}),
+        ("node.viewer_shortcut_set", {"type": 'SIX', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 6)]}),
+        ("node.viewer_shortcut_get", {"type": 'SEVEN', "value": 'PRESS'}, {"properties": [("viewer_index", 7)]}),
+        ("node.viewer_shortcut_set", {"type": 'SEVEN', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 7)]}),
+        ("node.viewer_shortcut_get", {"type": 'EIGHT', "value": 'PRESS'}, {"properties": [("viewer_index", 8)]}),
+        ("node.viewer_shortcut_set", {"type": 'EIGHT', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 8)]}),
+        ("node.viewer_shortcut_get", {"type": 'NINE', "value": 'PRESS'}, {"properties": [("viewer_index", 9)]}),
+        ("node.viewer_shortcut_set", {"type": 'NINE', "value": 'PRESS', 'ctrl': True},
+         {"properties": [("viewer_index", 9)]}),
     ])
 
     return keymap

scripts/startup/bl_operators/node.py

@@ -16,6 +16,7 @@ from bpy.props import (
     EnumProperty,
     FloatVectorProperty,
     StringProperty,
+    IntProperty,
 )
 from mathutils import (
     Vector,
@@ -408,6 +409,104 @@ class NODE_OT_interface_item_remove(NodeInterfaceOperator, Operator):
         return {'FINISHED'}
 
 
+class NODE_OT_viewer_shortcut_set(Operator):
+    """Create a compositor viewer shortcut for the selected node by pressing ctrl+1,2,..9"""
+    bl_idname = "node.viewer_shortcut_set"
+    bl_label = "Fast Preview"
+    bl_options = {'REGISTER', 'UNDO'}
+
+    viewer_index: IntProperty(
+        name="Viewer Index",
+        description="Index corresponding to the shortcut, e.g. number key 1 corresponds to index 1 etc..")
+
+    def get_connected_viewer(self, node):
+        for out in node.outputs:
+            for link in out.links:
+                nv = link.to_node
+                if nv.type == 'VIEWER':
+                    return nv
+        return None
+
+    @classmethod
+    def poll(self, context):
+        return context.space_data.tree_type == 'CompositorNodeTree'
+
+    def execute(self, context):
+        nodes = context.space_data.edit_tree.nodes
+        links = context.space_data.edit_tree.links
+        selected_nodes = context.selected_nodes
+
+        if len(selected_nodes) == 0:
+            self.report({'ERROR'}, "Select a node to assign a shortcut")
+            return {'CANCELLED'}
+
+        fav_node = selected_nodes[0]
+
+        # Only viewer nodes can be set to favorites. However, the user can
+        # create a new favorite viewer by selecting any node and pressing ctrl+1.
+        old_active = nodes.active
+        if fav_node.type == 'VIEWER':
+            viewer_node = fav_node
+        else:
+            viewer_node = self.get_connected_viewer(fav_node)
+            if not viewer_node:
+                # Calling link_viewer() if a viewer node is connected will connect the next available socket to the viewer node.
+                # This behavior is not desired as we want to create a shortcut to the exisiting connected viewer node.
+                # Therefore link_viewer() is called only when no viewer node is connected.
+                bpy.ops.node.link_viewer()
+                viewer_node = self.get_connected_viewer(fav_node)
+
+        if not viewer_node:
+            self.report({'ERROR'}, "Unable to set shortcut, selected node is not a viewer node or does not support viewing")
+            return {'CANCELLED'}
+
+        # Use the node active status to enable this viewer node and disable others.
+        nodes.active = viewer_node
+        if old_active.type != 'VIEWER':
+            nodes.active = old_active
+
+        viewer_node.ui_shortcut = self.viewer_index
+        self.report({'INFO'}, "Assigned shortcut %i to %s" % (self.viewer_index, viewer_node.name))
+
+        return {'FINISHED'}
+
+
+class NODE_OT_viewer_shortcut_get(Operator):
+    """Activate a specific compositor viewer node using 1,2,..,9 keys"""
+    bl_idname = "node.viewer_shortcut_get"
+    bl_label = "Fast Preview"
+    bl_options = {'REGISTER', 'UNDO'}
+
+    viewer_index: IntProperty(
+        name="Viewer Index",
+        description="Index corresponding to the shortcut, e.g. number key 1 corresponds to index 1 etc..")
+
+    @classmethod
+    def poll(self, context):
+        return context.space_data.tree_type == 'CompositorNodeTree'
+
+    def execute(self, context):
+        nodes = context.space_data.edit_tree.nodes
+
+        # Get viewer node with exisiting shortcut.
+        viewer_node = None
+        for n in nodes:
+            if n.type == 'VIEWER' and n.ui_shortcut == self.viewer_index:
+                viewer_node = n
+
+        if not viewer_node:
+            self.report({'INFO'}, "Shortcut %i is not assigned to a Viewer node yet" % self.viewer_index)
+            return {'CANCELLED'}
+
+        # Use the node active status to enable this viewer node and disable others.
+        old_active = nodes.active
+        nodes.active = viewer_node
+        if old_active.type != "VIEWER":
+            nodes.active = old_active
+
+        return {'FINISHED'}
+
+
 class NODE_FH_image_node(FileHandler):
     bl_idname = "NODE_FH_image_node"
     bl_label = "Image node"
@@ -438,4 +537,6 @@ classes = (
     NODE_OT_interface_item_duplicate,
     NODE_OT_interface_item_remove,
     NODE_OT_tree_path_parent,
+    NODE_OT_viewer_shortcut_get,
+    NODE_OT_viewer_shortcut_set,
 )

source/blender/blenkernel/intern/node.cc

@@ -3674,6 +3674,9 @@ void node_tree_set_output(bNodeTree *ntree)
         /* same type, exception for viewer */
         const bool tnode_is_output = tnode->type_legacy == CMP_NODE_VIEWER;
         const bool compositor_case = is_compositor && tnode_is_output && node_is_output;
+        const bool has_same_shortcut = compositor_case && node != tnode &&
+                                       tnode->custom1 == node->custom1 &&
+                                       tnode->custom1 != NODE_VIEWER_SHORTCUT_NONE;
         if (tnode->type_legacy == node->type_legacy || compositor_case) {
           if (tnode->flag & NODE_DO_OUTPUT) {
             output++;
@@ -3682,6 +3685,9 @@ void node_tree_set_output(bNodeTree *ntree)
             }
           }
         }
+        if (has_same_shortcut) {
+          tnode->custom1 = NODE_VIEWER_SHORTCUT_NONE;
+        }
       }
 
       if (output == 0) {

source/blender/blenloader/intern/versioning_400.cc

@@ -1283,6 +1283,17 @@ static void do_version_color_to_float_conversion(bNodeTree *node_tree)
   }
 }
 
+static void do_version_viewer_shortcut(bNodeTree *node_tree)
+{
+  LISTBASE_FOREACH_MUTABLE (bNode *, node, &node_tree->nodes) {
+    if (node->type_legacy != CMP_NODE_VIEWER) {
+      continue;
+    }
+    /* custom1 was previously used for Tile Order for the Tiled Compositor. */
+    node->custom1 = NODE_VIEWER_SHORTCUT_NONE;
+  }
+}
+
 static bool all_scenes_use(Main *bmain, const blender::Span<const char *> engines)
 {
   if (!bmain->scenes.first) {
@@ -5807,6 +5818,15 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
     }
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 404, 27)) {
+    FOREACH_NODETREE_BEGIN (bmain, ntree, id) {
+      if (ntree->type == NTREE_COMPOSIT) {
+        do_version_viewer_shortcut(ntree);
+      }
+    }
+    FOREACH_NODETREE_END;
+  }
+
   /* Always run this versioning; meshes are written with the legacy format which always needs to
    * be converted to the new format on file load. Can be moved to a subversion check in a larger
    * breaking release. */

source/blender/editors/space_node/node_draw.cc

@@ -3268,6 +3268,36 @@ static void node_draw_extra_info_panel(const bContext &C,
   }
 }
 
+static short get_viewer_shortcut_icon(const bNode &node)
+{
+  BLI_assert(node.is_type("CompositorNodeViewer"));
+  switch (node.custom1) {
+    case NODE_VIEWER_SHORTCUT_NONE:
+      /* No change by default. */
+      return node.typeinfo->ui_icon;
+    case NODE_VIEWER_SHORCTUT_SLOT_1:
+      return ICON_EVENT_ONEKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_2:
+      return ICON_EVENT_TWOKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_3:
+      return ICON_EVENT_THREEKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_4:
+      return ICON_EVENT_FOURKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_5:
+      return ICON_EVENT_FIVEKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_6:
+      return ICON_EVENT_SIXKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_7:
+      return ICON_EVENT_SEVENKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_8:
+      return ICON_EVENT_EIGHTKEY;
+    case NODE_VIEWER_SHORCTUT_SLOT_9:
+      return ICON_EVENT_NINEKEY;
+  }
+
+  return node.typeinfo->ui_icon;
+}
+
 static void node_draw_basis(const bContext &C,
                             TreeDrawContext &tree_draw_ctx,
                             const View2D &v2d,
@@ -3461,6 +3491,25 @@ static void node_draw_basis(const bContext &C,
         but, node_toggle_button_cb, POINTER_FROM_INT(node.identifier), (void *)operator_idname);
     UI_block_emboss_set(&block, UI_EMBOSS);
   }
+  /* Viewer node shortcuts. */
+  if (node.is_type("CompositorNodeViewer")) {
+    short shortcut_icon = get_viewer_shortcut_icon(node);
+    iconofs -= iconbutw;
+    UI_block_emboss_set(&block, UI_EMBOSS_NONE);
+    uiDefIconBut(&block,
+                 UI_BTYPE_BUT,
+                 0,
+                 shortcut_icon,
+                 iconofs,
+                 rct.ymax - NODE_DY,
+                 iconbutw,
+                 UI_UNIT_Y,
+                 nullptr,
+                 0,
+                 0,
+                 "");
+    UI_block_emboss_set(&block, UI_EMBOSS);
+  }
 
   node_add_error_message_button(tree_draw_ctx, node, block, rct, iconofs);
 

source/blender/editors/space_node/node_relationships.cc

@@ -739,7 +739,7 @@ static int view_socket(const bContext &C,
   /* Try to find a viewer that is already active. */
   for (bNode *node : btree.all_nodes()) {
     if (is_viewer_node(*node)) {
-      if (node->flag & NODE_DO_OUTPUT) {
+      if (node->flag & NODE_DO_OUTPUT && node->custom1 == NODE_VIEWER_SHORTCUT_NONE) {
         viewer_node = node;
         break;
       }
@@ -759,7 +759,7 @@ static int view_socket(const bContext &C,
 
   if (viewer_node == nullptr) {
     for (bNode *node : btree.all_nodes()) {
-      if (is_viewer_node(*node)) {
+      if (is_viewer_node(*node) && node->custom1 == NODE_VIEWER_SHORTCUT_NONE) {
         viewer_node = node;
         break;
       }

source/blender/makesdna/DNA_node_types.h

@@ -353,6 +353,21 @@ typedef struct bNodePanelState {
 #endif
 } bNodePanelState;
 
+typedef enum eViewerNodeShortcut {
+  NODE_VIEWER_SHORTCUT_NONE = 0,
+  /* Users can set custom keys to shortcuts,
+   * but shortcuts should always be referred to as enums. */
+  NODE_VIEWER_SHORCTUT_SLOT_1 = 1,
+  NODE_VIEWER_SHORCTUT_SLOT_2 = 2,
+  NODE_VIEWER_SHORCTUT_SLOT_3 = 3,
+  NODE_VIEWER_SHORCTUT_SLOT_4 = 4,
+  NODE_VIEWER_SHORCTUT_SLOT_5 = 5,
+  NODE_VIEWER_SHORCTUT_SLOT_6 = 6,
+  NODE_VIEWER_SHORCTUT_SLOT_7 = 7,
+  NODE_VIEWER_SHORCTUT_SLOT_8 = 8,
+  NODE_VIEWER_SHORCTUT_SLOT_9 = 9
+} eViewerNodeShortcut;
+
 typedef enum NodeWarningPropagation {
   NODE_WARNING_PROPAGATION_ALL = 0,
   NODE_WARNING_PROPAGATION_NONE = 1,

source/blender/makesrna/intern/rna_nodetree.cc

@@ -1356,6 +1356,20 @@ static void rna_NodeTree_active_node_set(PointerRNA *ptr,
   }
 }
 
+static void rna_Node_shortcut_node_set(PointerRNA *ptr, int value)
+{
+  bNode *curr_node = static_cast<bNode *>(ptr->data);
+  bNodeTree &ntree = curr_node->owner_tree();
+
+  /* Avoid having two nodes with the same shortcut. */
+  for (bNode *node : ntree.all_nodes()) {
+    if (node->is_type("CompositorNodeViewer") && node->custom1 == value) {
+      node->custom1 = NODE_VIEWER_SHORTCUT_NONE;
+    }
+  }
+  curr_node->custom1 = value;
+}
+
 static bNodeLink *rna_NodeTree_link_new(bNodeTree *ntree,
                                         Main *bmain,
                                         ReportList *reports,
@@ -9125,6 +9139,14 @@ static void def_cmp_viewer(BlenderRNA * /*brna*/, StructRNA *srna)
       "Use Alpha",
       "Colors are treated alpha premultiplied, or colors output straight (alpha gets set to 1)");
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+  prop = RNA_def_property(srna, "ui_shortcut", PROP_INT, PROP_NONE);
+  RNA_def_property_int_sdna(prop, nullptr, "custom1");
+  RNA_def_property_int_funcs(prop, nullptr, "rna_Node_shortcut_node_set", nullptr);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_IGNORE);
+  RNA_def_property_int_default(prop, NODE_VIEWER_SHORTCUT_NONE);
+  RNA_def_property_update(prop, NC_NODE | ND_DISPLAY, nullptr);
 }
 
 static void def_cmp_composite(BlenderRNA * /*brna*/, StructRNA *srna)

source/blender/nodes/composite/nodes/node_composite_viewer.cc

@@ -40,6 +40,7 @@ static void node_composit_init_viewer(bNodeTree * /*ntree*/, bNode *node)
   ImageUser *iuser = MEM_cnew<ImageUser>(__func__);
   node->storage = iuser;
   iuser->sfra = 1;
+  node->custom1 = NODE_VIEWER_SHORTCUT_NONE;
 
   node->id = (ID *)BKE_image_ensure_viewer(G.main, IMA_TYPE_COMPOSITE, "Viewer Node");
 }