Refactor: move bScreen .blend I/O to IDTypeInfo callbacks

I could not easily move `direct_link_screen` yet, because it
has a return value. That has to be solved differently at some point.

4 files changed, 55 insertions, 43 deletions

diff --git a/source/blender/blenkernel/intern/screen.c b/source/blender/blenkernel/intern/screen.c
index cfe52dd40e6..a357b5d98fb 100644
--- a/source/blender/blenkernel/intern/screen.c
+++ b/source/blender/blenkernel/intern/screen.c
@@ -56,6 +56,7 @@
 #include "BKE_icons.h"
 #include "BKE_idprop.h"
 #include "BKE_idtype.h"
+#include "BKE_lib_id.h"
 #include "BKE_lib_query.h"
 #include "BKE_node.h"
 #include "BKE_screen.h"
@@ -236,6 +237,40 @@ static void screen_foreach_id(ID *id, LibraryForeachIDData *data)
   }
 }
 
+static void screen_blend_write(BlendWriter *writer, ID *id, const void *id_address)
+{
+  bScreen *screen = (bScreen *)id;
+  /* Screens are reference counted, only saved if used by a workspace. */
+  if (screen->id.us > 0 || BLO_write_is_undo(writer)) {
+    /* write LibData */
+    /* in 2.50+ files, the file identifier for screens is patched, forward compatibility */
+    BLO_write_struct_at_address_with_filecode(writer, ID_SCRN, bScreen, id_address, screen);
+    BKE_id_blend_write(writer, &screen->id);
+
+    BKE_previewimg_blend_write(writer, screen->preview);
+
+    /* direct data */
+    BKE_screen_area_map_blend_write(writer, AREAMAP_FROM_SCREEN(screen));
+  }
+}
+
+/* note: file read without screens option G_FILE_NO_UI;
+ * check lib pointers in call below */
+static void screen_blend_read_lib(BlendLibReader *reader, ID *id)
+{
+  bScreen *screen = (bScreen *)id;
+  /* deprecated, but needed for versioning (will be NULL'ed then) */
+  BLO_read_id_address(reader, screen->id.lib, &screen->scene);
+
+  screen->animtimer = NULL; /* saved in rare cases */
+  screen->tool_tip = NULL;
+  screen->scrubbing = false;
+
+  LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+    BKE_screen_area_blend_read_lib(reader, &screen->id, area);
+  }
+}
+
 IDTypeInfo IDType_ID_SCR = {
     .id_code = ID_SCR,
     .id_filter = 0,
@@ -253,9 +288,10 @@ IDTypeInfo IDType_ID_SCR = {
     .foreach_id = screen_foreach_id,
     .foreach_cache = NULL,
 
-    .blend_write = NULL,
+    .blend_write = screen_blend_write,
+    /* Cannot be used yet, because #direct_link_screen has a return value. */
     .blend_read_data = NULL,
-    .blend_read_lib = NULL,
+    .blend_read_lib = screen_blend_read_lib,
     .blend_read_expand = NULL,
 };
 
diff --git a/source/blender/blenloader/BLO_read_write.h b/source/blender/blenloader/BLO_read_write.h
index 001b1c8b8a9..56b51bf3096 100644
--- a/source/blender/blenloader/BLO_read_write.h
+++ b/source/blender/blenloader/BLO_read_write.h
@@ -106,6 +106,14 @@ void BLO_write_struct_at_address_by_id(BlendWriter *writer,
   BLO_write_struct_at_address_by_id( \
       writer, BLO_get_struct_id(writer, struct_name), address, data_ptr)
 
+/* Write single struct at address and specify a filecode. */
+void BLO_write_struct_at_address_by_id_with_filecode(
+    BlendWriter *writer, int filecode, int struct_id, const void *address, const void *data_ptr);
+#define BLO_write_struct_at_address_with_filecode( \
+    writer, filecode, struct_name, address, data_ptr) \
+  BLO_write_struct_at_address_by_id_with_filecode( \
+      writer, filecode, BLO_get_struct_id(writer, struct_name), address, data_ptr)
+
 /* Write struct array. */
 void BLO_write_struct_array_by_name(BlendWriter *writer,
                                     const char *struct_name,
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 466243d4e52..6f305a5613f 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -4753,22 +4753,6 @@ static void lib_link_windowmanager(BlendLibReader *reader, wmWindowManager *wm)
 /** \name Read ID: Screen
  * \{ */
 
-/* note: file read without screens option G_FILE_NO_UI;
- * check lib pointers in call below */
-static void lib_link_screen(BlendLibReader *reader, bScreen *screen)
-{
-  /* deprecated, but needed for versioning (will be NULL'ed then) */
-  BLO_read_id_address(reader, screen->id.lib, &screen->scene);
-
-  screen->animtimer = NULL; /* saved in rare cases */
-  screen->tool_tip = NULL;
-  screen->scrubbing = false;
-
-  LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
-    BKE_screen_area_blend_read_lib(reader, &screen->id, area);
-  }
-}
-
 /* how to handle user count on pointer restore */
 typedef enum ePointerUserMode {
   USER_IGNORE = 0, /* ignore user count */
@@ -6158,11 +6142,6 @@ static void lib_link_all(FileData *fd, Main *bmain)
       case ID_OB:
         lib_link_object(&reader, (Object *)id);
         break;
-      case ID_SCR:
-        /* DO NOT skip screens here, 3D viewport may contains pointers
-         * to other ID data (like #View3D.ob_center)! See T41411. */
-        lib_link_screen(&reader, (bScreen *)id);
-        break;
       case ID_IP:
         /* XXX deprecated... still needs to be maintained for version patches still. */
         lib_link_ipo(&reader, (Ipo *)id);
@@ -6170,6 +6149,7 @@ static void lib_link_all(FileData *fd, Main *bmain)
       case ID_LI:
         lib_link_library(&reader, (Library *)id); /* Only init users. */
         break;
+      case ID_SCR:
       case ID_PA:
       case ID_GR:
       case ID_ME:
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index 1a5310b82ad..bcfc5778f1d 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -1662,22 +1662,6 @@ static void write_windowmanager(BlendWriter *writer, wmWindowManager *wm, const
   }
 }
 
-static void write_screen(BlendWriter *writer, bScreen *screen, const void *id_address)
-{
-  /* Screens are reference counted, only saved if used by a workspace. */
-  if (screen->id.us > 0 || BLO_write_is_undo(writer)) {
-    /* write LibData */
-    /* in 2.50+ files, the file identifier for screens is patched, forward compatibility */
-    writestruct_at_address(writer->wd, ID_SCRN, bScreen, 1, id_address, screen);
-    BKE_id_blend_write(writer, &screen->id);
-
-    BKE_previewimg_blend_write(writer, screen->preview);
-
-    /* direct data */
-    BKE_screen_area_map_blend_write(writer, AREAMAP_FROM_SCREEN(screen));
-  }
-}
-
 static void write_workspace(BlendWriter *writer, WorkSpace *workspace, const void *id_address)
 {
   BLO_write_id_struct(writer, WorkSpace, id_address, &workspace->id);
@@ -1957,15 +1941,13 @@ static bool write_file_handle(Main *mainvar,
           case ID_WS:
             write_workspace(&writer, (WorkSpace *)id_buffer, id);
             break;
-          case ID_SCR:
-            write_screen(&writer, (bScreen *)id_buffer, id);
-            break;
           case ID_SCE:
             write_scene(&writer, (Scene *)id_buffer, id);
             break;
           case ID_OB:
             write_object(&writer, (Object *)id_buffer, id);
             break;
+          case ID_SCR:
           case ID_PA:
           case ID_GR:
           case ID_ME:
@@ -2302,7 +2284,13 @@ void BLO_write_struct_at_address_by_id(BlendWriter *writer,
                                        const void *address,
                                        const void *data_ptr)
 {
-  writestruct_at_address_nr(writer->wd, DATA, struct_id, 1, address, data_ptr);
+  BLO_write_struct_at_address_by_id_with_filecode(writer, DATA, struct_id, address, data_ptr);
+}
+
+void BLO_write_struct_at_address_by_id_with_filecode(
+    BlendWriter *writer, int filecode, int struct_id, const void *address, const void *data_ptr)
+{
+  writestruct_at_address_nr(writer->wd, filecode, struct_id, 1, address, data_ptr);
 }
 
 void BLO_write_struct_array_by_id(BlendWriter *writer,