Index: PORTING
==================================================================
--- PORTING
+++ PORTING
@@ -249,5 +249,23 @@
 
 === Mac OS X ===
 
 (TODO)
 
+
+=== Sandboxing ===
+
+Many sandbox systems have problems, such as:
+
+* Assumes all text is Unicode.
+
+* Cannot request a command to use with popen (or from configuration files).
+
+* When asking for a file, cannot also include certain other files whose
+names are done by adding additional text onto the end of the name (this is
+needed for SQLite to work, and also for non-composite puzzle sets in Free
+Hero Mesh).
+
+* Assumes a desktop environment.
+
+Therefore, if it is to be used, a better one should be made up.
+

Index: class.c
==================================================================
--- class.c
+++ class.c
@@ -123,10 +123,11 @@
 static InputStack*inpstack;
 static MacroStack*macstack;
 static TokenList**macros;
 static LabelStack*labelstack;
 static Uint16*labelptr;
+static Uint8 dense[8];
 
 #define ParseError(a,...) fatal("On line %d: " a,linenum,##__VA_ARGS__)
 
 static const unsigned char chkind[256]={
   ['$']=1, ['!']=1, ['\'']=1, ['#']=1, ['@']=1, ['%']=1, ['&']=1, [':']=1, ['^']=1,
@@ -2152,10 +2153,16 @@
       ParseError("Invalid directly inside of a class definition\n");
     }
   }
   end_label_stack(cl->codes,hash);
   if(!cl->nimages && !(cl->cflags&CF_GROUP)) cl->oflags|=OF_INVISIBLE;
+  if(cl->collisionLayers && *dense && !cl->density) {
+    for(i=0;i<8;i++) if(dense[i] && ((1<<i)&cl->collisionLayers)) {
+      cl->density=dense[i];
+      break;
+    }
+  }
   if(main_options['C']) dump_class(cla,ptr,hash);
   if(main_options['H']) {
     for(i=0;i<LOCAL_HASH_SIZE;i++) if(hash[i].id) printf(" \"%s\": %04X\n",hash[i].txt,hash[i].id);
   }
   for(i=0;i<LOCAL_HASH_SIZE;i++) {
@@ -2518,10 +2525,21 @@
     }
     putchar('\n');
     printf("---\n\n");
   }
 }
+
+static void parse_density_block(void) {
+  int i;
+  for(i=0;i<8;i++) {
+    nxttok();
+    if(tokent==TF_CLOSE) return;
+    if(tokent!=TF_INT || tokenv<1 || tokenv>255) ParseError("Number 1-255 or close parenthesis expected\n");
+    dense[i]=tokenv;
+  }
+  ParseError("Too many global density numbers are specified\n");
+}
 
 void load_classes(void) {
   int i;
   int gloptr=0;
   Hash*glolocalhash;
@@ -2692,10 +2710,13 @@
         case OP_INPUTXY:
           has_xy_input=1;
           nxttok();
           if(tokent!=TF_CLOSE) ParseError("Expected close parenthesis\n");
           break;
+        case OP_DENSITY:
+          parse_density_block();
+          break;
         default:
           ParseError("Invalid top level definition: %s\n",tokenstr);
       }
     } else {
       ParseError("Invalid top level definition\n");

Index: class.doc
==================================================================
--- class.doc
+++ class.doc
@@ -287,10 +287,16 @@
 
 (CollisionLayers <userflags...>)
   Define user flags as CollisionLayers bits; the first defined flag is
   bit0. Up to 8 flags can be defined in this way.
 
+(Density <numbers...>)
+  Define the default Density settings for classes that use the collision
+  layers. Each number must be in range 1 to 255, and there cannot be more
+  than eight density numbers defined. Their order is the same as the order
+  of the user flags in the (CollisionLayers) block.
+
 (InputXY <options...>)
   Enables coordinate input. Currently there are no options, so the options
   must be left blank. See the documentation about the CLICK message for
   more details about coordinate input.