Compositor: add asset shelf

Add an asset shelf to the compositor node editor.

This is part of simplifying the compositing workflow:
https://projects.blender.org/blender/blender/issues/134214.

The reasoning is:
- Assets will help users get started more easily with compositing
- Assets will help keeping users within Blender and use the compositor
instead of doing post processing in a different software.
- The asset shelf is better than the asset browser because it has a
better user interface; it's easily hidable and doesn't take much space

The asset shelf is hidden by default in this PR, since we have no
assets yet.

Previously, a similar implementation was proposed for all node editors,
see https://projects.blender.org/blender/blender/pulls/110589.
We didn't move forward with this PR for the following reasons:
- For geometry nodes, no concrete use case was known/proposed
- The PR didn't intend to actually show the asset shelf, only
implement the possibility that it can be shown in node editors

Known Issues:
- Can't hide the asset shelf if region overlap is off: #129737

Pull Request: https://projects.blender.org/blender/blender/pulls/138983

scripts/startup/bl_ui/space_node.py

@@ -1184,6 +1184,20 @@ def node_panel(cls):
     return node_cls
 
 
+class NODE_AST_compositor(bpy.types.AssetShelf):
+    bl_space_type = 'NODE_EDITOR'
+    bl_region_type = 'UI'
+
+    @classmethod
+    def poll(cls, context):
+        return context.space_data.tree_type == 'CompositorNodeTree'
+
+    @classmethod
+    def asset_poll(cls, asset):
+        compositing_type = bpy.types.NodeTree.bl_rna.properties["type"].enum_items["COMPOSITING"]
+        return asset.id_type == 'NODETREE' and asset.metadata.get("type") == compositing_type.value
+
+
 classes = (
     NODE_HT_header,
     NODE_MT_editor_menus,
@@ -1216,6 +1230,7 @@ classes = (
     NODE_PT_overlay,
     NODE_PT_active_node_properties,
     NODE_PT_gizmo_display,
+    NODE_AST_compositor,
 
     node_panel(EEVEE_MATERIAL_PT_settings),
     node_panel(EEVEE_MATERIAL_PT_settings_surface),

source/blender/blenkernel/BKE_blender_version.h

@@ -27,7 +27,7 @@
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 45
+#define BLENDER_FILE_SUBVERSION 46
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenloader/intern/versioning_500.cc

@@ -1961,6 +1961,42 @@ void blo_do_versions_500(FileData * /*fd*/, Library * /*lib*/, Main *bmain)
     FOREACH_NODETREE_END;
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 500, 46)) {
+    LISTBASE_FOREACH (bScreen *, screen, &bmain->screens) {
+      LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+        LISTBASE_FOREACH (SpaceLink *, sl, &area->spacedata) {
+          if (sl->spacetype != SPACE_NODE) {
+            continue;
+          }
+          const SpaceNode *snode = reinterpret_cast<SpaceNode *>(sl);
+          if (!STREQ(snode->tree_idname, "CompositorNodeTree")) {
+            continue;
+          }
+
+          ListBase *regionbase = (sl == area->spacedata.first) ? &area->regionbase :
+                                                                 &sl->regionbase;
+
+          if (ARegion *new_shelf_region = do_versions_add_region_if_not_found(
+                  regionbase,
+                  RGN_TYPE_ASSET_SHELF,
+                  "Asset shelf for compositing (versioning)",
+                  RGN_TYPE_HEADER))
+          {
+            new_shelf_region->alignment = RGN_ALIGN_BOTTOM;
+          }
+          if (ARegion *new_shelf_header = do_versions_add_region_if_not_found(
+                  regionbase,
+                  RGN_TYPE_ASSET_SHELF_HEADER,
+                  "Asset shelf header for compositing (versioning)",
+                  RGN_TYPE_ASSET_SHELF))
+          {
+            new_shelf_header->alignment = RGN_ALIGN_BOTTOM | RGN_ALIGN_HIDE_WITH_PREV;
+          }
+        }
+      }
+    }
+  }
+
   /**
    * 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/screen/area.cc

@@ -1433,7 +1433,12 @@ bool ED_region_is_overlap(int spacetype, int regiontype)
   }
   if (U.uiflag2 & USER_REGION_OVERLAP) {
     if (spacetype == SPACE_NODE) {
-      if (ELEM(regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI)) {
+      if (ELEM(regiontype,
+               RGN_TYPE_TOOLS,
+               RGN_TYPE_UI,
+               RGN_TYPE_ASSET_SHELF,
+               RGN_TYPE_ASSET_SHELF_HEADER))
+      {
         return true;
       }
     }

source/blender/editors/space_node/CMakeLists.txt

@@ -12,6 +12,7 @@ set(INC
   ../../compositor/utilities
   ../../makesrna
   ../../nodes/geometry/include
+  ../asset
 
   # RNA_prototypes.hh
   ${CMAKE_BINARY_DIR}/source/blender/makesrna

source/blender/editors/space_node/space_node.cc

@@ -42,6 +42,7 @@
 
 #include "BLT_translation.hh"
 
+#include "ED_asset_shelf.hh"
 #include "ED_image.hh"
 #include "ED_node.hh"
 #include "ED_node_preview.hh"
@@ -1048,6 +1049,21 @@ static SpaceLink *node_create(const ScrArea * /*area*/, const Scene * /*scene*/)
   region->regiontype = RGN_TYPE_HEADER;
   region->alignment = (U.uiflag & USER_HEADER_BOTTOM) ? RGN_ALIGN_BOTTOM : RGN_ALIGN_TOP;
 
+  /* asset shelf */
+  region = BKE_area_region_new();
+
+  BLI_addtail(&snode->regionbase, region);
+  region->regiontype = RGN_TYPE_ASSET_SHELF;
+  region->alignment = RGN_ALIGN_BOTTOM;
+  region->flag |= RGN_FLAG_HIDDEN;
+
+  /* asset shelf header */
+  region = BKE_area_region_new();
+
+  BLI_addtail(&snode->regionbase, region);
+  region->regiontype = RGN_TYPE_ASSET_SHELF_HEADER;
+  region->alignment = RGN_ALIGN_BOTTOM | RGN_ALIGN_HIDE_WITH_PREV;
+
   /* buttons/list view */
   region = BKE_area_region_new();
 
@@ -2212,10 +2228,21 @@ static void node_space_blend_write(BlendWriter *writer, SpaceLink *sl)
   }
 }
 
+static void node_asset_shelf_region_init(wmWindowManager *wm, ARegion *region)
+{
+  using namespace blender::ed;
+  wmKeyMap *keymap = WM_keymap_ensure(
+      wm->defaultconf, "Node Generic", SPACE_NODE, RGN_TYPE_WINDOW);
+  WM_event_add_keymap_handler(&region->runtime->handlers, keymap);
+
+  asset::shelf::region_init(wm, region);
+}
+
 }  // namespace blender::ed::space_node
 
 void ED_spacetype_node()
 {
+  using namespace blender::ed;
   using namespace blender::ed::space_node;
 
   std::unique_ptr<SpaceType> st = std::make_unique<SpaceType>();
@@ -2273,6 +2300,36 @@ void ED_spacetype_node()
 
   BLI_addhead(&st->regiontypes, art);
 
+  /* regions: asset shelf */
+  art = MEM_callocN<ARegionType>("spacetype node asset shelf region");
+  art->regionid = RGN_TYPE_ASSET_SHELF;
+  art->keymapflag = ED_KEYMAP_UI | ED_KEYMAP_ASSET_SHELF | ED_KEYMAP_FRAMES;
+  art->duplicate = asset::shelf::region_duplicate;
+  art->free = asset::shelf::region_free;
+  art->on_poll_success = asset::shelf::region_on_poll_success;
+  art->listener = asset::shelf::region_listen;
+  art->message_subscribe = asset::shelf::region_message_subscribe;
+  art->poll = asset::shelf::regions_poll;
+  art->snap_size = asset::shelf::region_snap;
+  art->on_user_resize = asset::shelf::region_on_user_resize;
+  art->context = asset::shelf::context;
+  art->init = node_asset_shelf_region_init;
+  art->layout = asset::shelf::region_layout;
+  art->draw = asset::shelf::region_draw;
+  BLI_addhead(&st->regiontypes, art);
+
+  /* regions: asset shelf header */
+  art = MEM_callocN<ARegionType>("spacetype node asset shelf header region");
+  art->regionid = RGN_TYPE_ASSET_SHELF_HEADER;
+  art->keymapflag = ED_KEYMAP_UI | ED_KEYMAP_ASSET_SHELF | ED_KEYMAP_VIEW2D | ED_KEYMAP_FOOTER;
+  art->init = asset::shelf::header_region_init;
+  art->poll = asset::shelf::regions_poll;
+  art->draw = asset::shelf::header_region;
+  art->listener = asset::shelf::header_region_listen;
+  art->context = asset::shelf::context;
+  BLI_addhead(&st->regiontypes, art);
+  asset::shelf::types_register(art, SPACE_NODE);
+
   /* regions: list-view/buttons */
   art = MEM_callocN<ARegionType>("spacetype node region");
   art->regionid = RGN_TYPE_UI;

source/blender/makesrna/intern/rna_space.cc

@@ -8064,7 +8064,8 @@ static void rna_def_space_node(BlenderRNA *brna)
   RNA_def_struct_sdna(srna, "SpaceNode");
   RNA_def_struct_ui_text(srna, "Space Node Editor", "Node editor space data");
 
-  rna_def_space_generic_show_region_toggles(srna, (1 << RGN_TYPE_TOOLS) | (1 << RGN_TYPE_UI));
+  rna_def_space_generic_show_region_toggles(
+      srna, (1 << RGN_TYPE_TOOLS) | (1 << RGN_TYPE_UI) | (1 << RGN_TYPE_ASSET_SHELF));
 
   prop = RNA_def_property(srna, "tree_type", PROP_ENUM, PROP_NONE);
   RNA_def_property_enum_items(prop, rna_enum_dummy_DEFAULT_items);

source/blender/makesrna/intern/rna_userdef.cc

@@ -3276,6 +3276,7 @@ static void rna_def_userdef_theme_space_node(BlenderRNA *brna)
 
   rna_def_userdef_theme_spaces_main(srna);
   rna_def_userdef_theme_spaces_region_main(srna);
+  rna_def_userdef_theme_spaces_list_main(srna);
 
   prop = RNA_def_property(srna, "grid", PROP_FLOAT, PROP_COLOR_GAMMA);
   RNA_def_property_array(prop, 3);