diff -r 7a02afa6d25a src/settings_gui.cpp
--- a/src/settings_gui.cpp	Sun Nov 16 12:05:36 2008 +0100
+++ b/src/settings_gui.cpp	Sun Nov 16 12:39:19 2008 +0100
@@ -590,14 +590,23 @@
 enum PatchEntryFlags {
 	PEF_LEFT_DEPRESSED  = 0x01, ///< Of a numeric patch entry, the left button is depressed
 	PEF_RIGHT_DEPRESSED = 0x02, ///< Of a numeric patch entry, the right button is depressed
+
+	/* Entry kind */
+	PEF_SETTING_KIND = 0x10, ///< Entry kind: Entry is a setting
+	PEF_SUBTREE_KIND = 0x20, ///< Entry kind: Entry is a sub-tree
+	PEF_KIND_MASK    = (PEF_SETTING_KIND | PEF_SUBTREE_KIND) ///< Bit-mask for fetching entry kind
 };
 
 /** Data structure describing a single patch in a tab */
 struct PatchEntry {
 	uint16 flags;               ///< Flags of the pach entry. @see PatchEntryFlags
-	const char *name;           ///< Name of the setting
-	const SettingDesc *setting; ///< Setting description of the patch
-	uint index;                 ///< Index of the setting in the settings table
+	union {
+		struct {
+			const char *name;           ///< Name of the setting
+			const SettingDesc *setting; ///< Setting description of the patch
+			uint index;                 ///< Index of the setting in the settings table
+		} entry;
+	} d;
 
 	PatchEntry(const char *nm);
 
@@ -624,13 +633,24 @@
 /* == PatchEntry methods == */
 
 /** Constructor a patch setting */
-PatchEntry::PatchEntry(const char *nm): flags(0), name(nm), setting(NULL), index(0) { }
+PatchEntry::PatchEntry(const char *nm)
+{
+	flags = PEF_SETTING_KIND;
+	d.entry.name = nm;
+	d.entry.setting = NULL;
+	d.entry.index = 0;
+}
 
 /** Initialization of a patch entry */
 void PatchEntry::Init()
 {
-	setting = GetPatchFromName(name, &index);
-	assert(setting != NULL);
+	switch(flags & PEF_KIND_MASK) {
+		case PEF_SETTING_KIND:
+			d.entry.setting = GetPatchFromName(d.entry.name, &d.entry.index);
+			assert(d.entry.setting != NULL);
+			break;
+		default: NOT_REACHED();
+	}
 }
 
 /**
@@ -641,8 +661,14 @@
  */
 void PatchEntry::Draw(GameSettings *patches_ptr, int x, int y)
 {
-	int state = flags & (PEF_LEFT_DEPRESSED | PEF_RIGHT_DEPRESSED);
-	DrawPatch(patches_ptr, setting, x, y, state);
+	switch(flags & PEF_KIND_MASK) {
+		case PEF_SETTING_KIND: {
+			int state = flags & (PEF_LEFT_DEPRESSED | PEF_RIGHT_DEPRESSED);
+			DrawPatch(patches_ptr, d.entry.setting, x, y, state);
+			break;
+		}
+		default: NOT_REACHED();
+	}
 }
 
 /**
@@ -977,7 +1003,8 @@
 
 				if (pe == NULL) return;  // Clicked below the last setting of the page
 
-				const SettingDesc *sd = pe->setting;
+				assert((pe->flags & PEF_KIND_MASK) == PEF_SETTING_KIND);
+				const SettingDesc *sd = pe->d.entry.setting;
 
 				/* return if action is only active in network, or only settable by server */
 				if (!(sd->save.conv & SLF_NETWORK_NO) && _networking && !_network_server) return;
@@ -1032,7 +1059,7 @@
 					}
 
 					if (value != oldvalue) {
-						SetPatchValue(pe->index, value);
+						SetPatchValue(pe->d.entry.index, value);
 						this->SetDirty();
 					}
 				} else {
@@ -1077,13 +1104,14 @@
 	{
 		if (!StrEmpty(str)) {
 			assert(valuewindow_entry != NULL);
-			const SettingDesc *sd = valuewindow_entry->setting;
+			assert((valuewindow_entry->flags & PEF_KIND_MASK) == PEF_SETTING_KIND);
+			const SettingDesc *sd = valuewindow_entry->d.entry.setting;
 			int32 value = atoi(str);
 
 			/* Save the correct currency-translated value */
 			if (sd->desc.flags & SGF_CURRENCY) value /= _currency->rate;
 
-			SetPatchValue(valuewindow_entry->index, value);
+			SetPatchValue(valuewindow_entry->d.entry.index, value);
 			this->SetDirty();
 		}
 	}