indxf: VIEWPORT needs to create a matching VX_TABLE_RECORD

TODO: and if the VIEWPORT is *Active, it needs to set HEADER.VX_TABLE_RECORD
On LAYOUT.active_viewport

Author: rurban

doc/LibreDWG.texi

@@ -734,6 +734,15 @@ All blocks are accessed via all other model_space BLOCK_HEADER's,
 holds a list of all table records, i.e. entries.  Each table record
 entry has a name and other common table fields.
 
+The VX table (also vport_entity table) is a special table until r2004
+for VIEWPORT entities, which are VPORT extensions, esp. for Paper
+Space, but have no old-style table records. So VX_CONTROL contains a
+list of matching VX_TABLE_RECORD's, which are pointed to by
+VIEWPORT.vport_entity_header handles. Likewise the VX_TABLE_RECORD
+object links in its viewport field back to the VIEWPORT. The VX table
+is not represented in DXF, on DXF import we need to create them with
+the VIEWPORT entities.
+
 @node EXTRAS
 @section EXTRAS entities section
 

examples/dwgadd.c

@@ -1718,6 +1718,7 @@ dwg_add_dat (Dwg_Data **dwgp, Bit_Chain *dat)
         CHK_MISSING_BLOCK_HEADER
         if (!dwg_is_valid_name (dwg, text))
           fn_error ("Invalid table record name\n");
+        // add's a VX also if <r2004
         ent = (lastent_t){ .u.viewport = dwg_add_VIEWPORT (hdr, text),
                            .type = DWG_TYPE_VIEWPORT };
       }

src/dwg.c

@@ -75,6 +75,7 @@ EXPORT int dwg_read_dxfb (Bit_Chain *restrict dat, Dwg_Data *restrict dwg);
 BITCODE_H
 dwg_find_tablehandle_silent (Dwg_Data *restrict dwg, const char *restrict name,
                              const char *restrict table);
+BITCODE_RLL dwg_new_handseed (Dwg_Data *restrict dwg);
 // used in encode.c
 void dwg_set_handle_size (Dwg_Handle *restrict hdl);
 void dwg_downgrade_MLINESTYLE (Dwg_Object_MLINESTYLE *o);
@@ -2213,6 +2214,14 @@ dwg_add_handleref_free (const BITCODE_RC code, const BITCODE_RLL absref)
   return ref;
 }
 
+BITCODE_RLL
+dwg_new_handseed (Dwg_Data *restrict dwg)
+{
+  BITCODE_RLL old = dwg->header_vars.HANDSEED->absolute_ref;
+  dwg->header_vars.HANDSEED->handleref.value++;
+  dwg->header_vars.HANDSEED->absolute_ref++;
+  return old;
+}
 // Not checking the header_vars entry, only searching the objects
 // Returning a hardowner ref (code 3) to it, as stored in header_vars.
 EXPORT BITCODE_H

src/dwg.spec

@@ -2535,7 +2535,7 @@ DWG_ENTITY (VIEWPORT)
 
   COMMON_ENTITY_HANDLE_DATA;
   VERSIONS (R_13b1, R_14) {
-    FIELD_HANDLE (vport_entity_header, 5, 0);
+    FIELD_HANDLE (vport_entity_header, 5, 0); // => VX
   }
   VERSIONS (R_2000b, R_2002) {
     HANDLE_VECTOR (frozen_layers, num_frozen_layers, 5, 341);
@@ -2546,7 +2546,7 @@ DWG_ENTITY (VIEWPORT)
     FIELD_HANDLE (clip_boundary, 5, 340);
   }
   VERSIONS (R_2000b, R_2002) {
-    FIELD_HANDLE (vport_entity_header, 5, 0);
+    FIELD_HANDLE (vport_entity_header, 5, 0);  // => VX
   }
   SINCE (R_2000b) {
     FIELD_HANDLE (named_ucs, 5, 345);

src/dwg_api.c

@@ -27088,13 +27088,25 @@ EXPORT Dwg_Entity_VIEWPORT *
 dwg_add_VIEWPORT (Dwg_Object_BLOCK_HEADER *restrict blkhdr,
                   const char *restrict name)
 {
-  API_ADD_ENTITY (VIEWPORT);
+  Dwg_Object_VX_TABLE_RECORD *vx = NULL;
+  API_ADD_PREP (VIEWPORT);
   if (dwg->header.version < R_11)
     {
       LOG_ERROR ("Invalid entity %s <r11", "VIEWPORT")
-      API_UNADD_ENTITY;
       return NULL;
     }
+  if (dwg->header.version < R_2004)
+    {
+      vx = dwg_add_VX (dwg, name);
+    }
+  API_ADD_ENTITY2 (VIEWPORT);
+  if (dwg->header.version < R_2004 && vx)
+    {
+      Dwg_Object *vxobj = dwg_obj_generic_to_object (vx, &error);
+      vx->is_on = 1;
+      vx->viewport = dwg_add_handleref (dwg, 4, obj->handle.value, NULL);
+      _obj->vport_entity_header = dwg_add_handleref (dwg, 5, vxobj ? vxobj->handle.value : 0, NULL);
+    }
   // TODO get defaults from name
   _obj->lens_length = 50.0;
   _obj->VIEWDIR.z = 1.0;

src/header_variables.spec

@@ -100,7 +100,8 @@
     }
   VERSIONS (R_13b1, R_2000)
     {
-      FIELD_HANDLE (VX_TABLE_RECORD, 5, 0); //current view
+      // => VX. VX.viewport <=> active_viewport in LAYOUT
+      FIELD_HANDLE (VX_TABLE_RECORD, 5, 0); // current view
     }
   SINCE (R_13b1)
     {

src/in_dxf.c

@@ -60,12 +60,16 @@ Dwg_Object *dwg_obj_generic_to_object (const void *restrict obj,
                                        int *restrict error);
 #endif
 // from dwg_api.c
-EXPORT Dwg_Object_DICTIONARY *
+Dwg_Object_DICTIONARY *
 dwg_add_DICTIONARY (Dwg_Data *restrict dwg,
                     const char *restrict name, /* the NOD entry */
                     const char *restrict text, /* maybe NULL */
                     const BITCODE_RLL absolute_ref);
+Dwg_Object_VX_TABLE_RECORD *
+dwg_add_VX (Dwg_Data *restrict dwg, const char *restrict name /* maybe NULL */);
 // from dwg.c
+BITCODE_RLL
+dwg_new_handseed (Dwg_Data *restrict dwg);
 BITCODE_H
 dwg_find_tablehandle_silent (Dwg_Data *restrict dwg, const char *restrict name,
                              const char *restrict table);
@@ -9345,6 +9349,27 @@ Dxf_Pair *new_object (
                 LOG_TRACE ("Reuse existing BLOCK_HEADER.*Model_Space %X [0]\n",
                            pair->value.u)
               }
+          // special-case VIEWPORT -> VX.
+          if (strEQc (name, "VIEWPORT") && dwg->header.version < R_2004
+              && dwg->header.version > R_11 && pair->code == 5)
+            {
+              Dwg_Object_VX_TABLE_RECORD *vx = dwg_add_VX (dwg, "");
+              Dwg_Object *vxobj = dwg_obj_generic_to_object (vx, &error);
+              Dwg_Entity_VIEWPORT *_vobj = obj->tio.entity->tio.VIEWPORT;
+              if (dwg->header_vars.HANDSEED)
+                {
+                  vxobj->handle.value = dwg_new_handseed (dwg);
+                }
+              // vx->is_on = 1;
+              vx->viewport
+                  = dwg_add_handleref (dwg, 4, pair->value.u, NULL);
+              LOG_TRACE ("VX_TABLE_RECORD.viewport = " FORMAT_REF " [H 4]\n",
+                         ARGS_REF (vx->viewport));
+              _vobj->vport_entity_header
+                  = dwg_add_handleref (dwg, 5, vxobj->handle.value, NULL);
+              LOG_TRACE ("VIEWPORT.vport_entity_header = " FORMAT_REF " [H 5]\n",
+                         ARGS_REF (_vobj->vport_entity_header));
+            }
             if (strNE (name, "DIMSTYLE") || pair->code == 105)
               {
                 obj->handle.value = pair->value.u;
@@ -12925,8 +12950,16 @@ dxf_entities_read (Bit_Chain *restrict dat, Dwg_Data *restrict dwg)
             }
           if (pair->code == 0 && pair->value.s)
             {
-              Dwg_Object *obj = &dwg->object[dwg->num_objects - 1];
+              BITCODE_BL last_ent = dwg->num_objects - 1;
+              Dwg_Object *obj = &dwg->object[last_ent];
               Dwg_Object_Entity *ent = obj->tio.entity;
+              // FIXUP hack for added VX and VX_CONTROL
+              while (obj->supertype != DWG_SUPERTYPE_ENTITY)
+                {
+                  last_ent--;
+                  obj = &dwg->object[last_ent];
+                  ent = obj->tio.entity;
+                }
               if (ent->ownerhandle)
                 {
                   if (ent->ownerhandle->absolute_ref == mspace)