First step to handle missing libs/datablocks when reading a file.

Idea is, instead of ignoring completely missing linked datablocks, to
create void placeholders for them.

That way, you can work on your file, save it, and find again your missing data once
lib becomes available again. Or you can edit missing lib's path (in Outliner),
save and reload the file, and you are done.

Also, Outliner now shows broken libraries (and placeholders) with a 'broken lib' icon.

Future plans are also to be able to relocate missing libs and reload them at runtime.

Code notes:
    - Placeholder ID is just a regular datablock of same type as expected linked one,
      with 'default' data, and a LIB_MISSING bitflag set.
    - To allow creation of such datablocks, creation of datablocks in BKE was split in two step:
        + Allocation of memory itself.
        + Setting of all internal data to default values.

See also the design task (T43351).

Reviewed by @campbellbarton, thanks a bunch!

Differential Revision: https://developer.blender.org/D1394

1 files changed, 120 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/library.c b/source/blender/blenkernel/intern/library.c
index d6b2a3cea29..f8f92825479 100644
--- a/source/blender/blenkernel/intern/library.c
+++ b/source/blender/blenkernel/intern/library.c
@@ -59,6 +59,7 @@
 #include "DNA_movieclip_types.h"
 #include "DNA_mask_types.h"
 #include "DNA_node_types.h"
+#include "DNA_object_types.h"
 #include "DNA_scene_types.h"
 #include "DNA_screen_types.h"
 #include "DNA_speaker_types.h"
@@ -648,7 +649,7 @@ int set_listbasepointers(Main *main, ListBase **lb)
  * Allocates and returns memory of the right size for the specified block type,
  * initialized to zero.
  */
-static ID *alloc_libblock_notest(short type)
+void *BKE_libblock_alloc_notest(short type)
 {
 	ID *id = NULL;
 	
@@ -770,7 +771,7 @@ void *BKE_libblock_alloc(Main *bmain, short type, const char *name)
 	ID *id = NULL;
 	ListBase *lb = which_libbase(bmain, type);
 	
-	id = alloc_libblock_notest(type);
+	id = BKE_libblock_alloc_notest(type);
 	if (id) {
 		BKE_main_lock(bmain);
 		BLI_addtail(lb, id);
@@ -785,6 +786,121 @@ void *BKE_libblock_alloc(Main *bmain, short type, const char *name)
 	return id;
 }
 
+/**
+ * Initialize an ID of given type, such that it has valid 'empty' data.
+ * ID is assumed to be just calloc'ed.
+ */
+void BKE_libblock_init_empty(ID *id)
+{
+	/* Note that only ID types that are not valid when filled of zero should have a callback here. */
+	switch (GS(id->name)) {
+		case ID_SCE:
+			BKE_scene_init((Scene *)id);
+			break;
+		case ID_LI:
+			/* Nothing to do. */
+			break;
+		case ID_OB:
+		{
+			Object *ob = (Object *)id;
+			ob->type = OB_EMPTY;
+			BKE_object_init(ob);
+			break;
+		}
+		case ID_ME:
+			BKE_mesh_init((Mesh *)id);
+			break;
+		case ID_CU:
+			BKE_curve_init((Curve *)id);
+			break;
+		case ID_MB:
+			BKE_mball_init((MetaBall *)id);
+			break;
+		case ID_MA:
+			BKE_material_init((Material *)id);
+			break;
+		case ID_TE:
+			BKE_texture_default((Tex *)id);
+			break;
+		case ID_IM:
+			/* Image is a bit complicated, for now assume NULLified im is OK. */
+			break;
+		case ID_LT:
+			BKE_lattice_init((Lattice *)id);
+			break;
+		case ID_LA:
+			BKE_lamp_init((Lamp *)id);
+			break;
+		case ID_SPK:
+			BKE_speaker_init((Speaker *)id);
+			break;
+		case ID_CA:
+			BKE_camera_init((Camera *)id);
+			break;
+		case ID_IP:
+			/* Should not be needed - animation from lib pre-2.5 is broken anyway. */
+			BLI_assert(0);
+			break;
+		case ID_KE:
+			/* Shapekeys are a complex topic too - they depend on their 'user' data type...
+			 * They are not linkable, though, so it should never reach here anyway. */
+			BLI_assert(0);
+			break;
+		case ID_WO:
+			BKE_world_init((World *)id);
+			break;
+		case ID_SCR:
+			/* Nothing to do. */
+			break;
+		case ID_VF:
+			BKE_vfont_init((VFont *)id);
+			break;
+		case ID_TXT:
+			BKE_text_init((Text *)id);
+			break;
+		case ID_SCRIPT:
+			BLI_assert(0);
+			break;
+		case ID_SO:
+			/* Another fuzzy case, think NULLified content is OK here... */
+			break;
+		case ID_GR:
+			/* Nothing to do. */
+			break;
+		case ID_AR:
+			/* Nothing to do. */
+			break;
+		case ID_AC:
+			/* Nothing to do. */
+			break;
+		case ID_NT:
+			ntreeInitDefault((bNodeTree *)id);
+			break;
+		case ID_BR:
+			BKE_brush_init((Brush *)id);
+			break;
+		case ID_PA:
+			/* Nothing to do. */
+			break;
+		case ID_PC:
+			/* Nothing to do. */
+			break;
+		case ID_WM:
+			/* We should never reach this. */
+			BLI_assert(0);
+			break;
+		case ID_GD:
+			/* Nothing to do. */
+			break;
+		case ID_MSK:
+			/* Nothing to do. */
+			break;
+		case ID_LS:
+			BKE_linestyle_init((FreestyleLineStyle *)id);
+			break;
+	}
+}
+
 /* by spec, animdata is first item after ID */
 /* and, trust that BKE_animdata_from_id() will only find AnimData for valid ID-types */
 static void id_copy_animdata(ID *id, const bool do_action)
@@ -838,7 +954,7 @@ void *BKE_libblock_copy_nolib(ID *id, const bool do_action)
 	ID *idn;
 	size_t idn_len;
 
-	idn = alloc_libblock_notest(GS(id->name));
+	idn = BKE_libblock_alloc_notest(GS(id->name));
 	assert(idn != NULL);
 
 	BLI_strncpy(idn->name, id->name, sizeof(idn->name));
@@ -1720,7 +1836,7 @@ void rename_id(ID *id, const char *name)
  */
 void name_uiprefix_id(char *name, const ID *id)
 {
-	name[0] = id->lib ? 'L' : ' ';
+	name[0] = id->lib ? (ID_MISSING(id) ? 'M' : 'L') : ' ';
 	name[1] = (id->flag & LIB_FAKEUSER) ? 'F' : ((id->us == 0) ? '0' : ' ');
 	name[2] = ' ';