(svn r22000) -Codechange: Introduce an enum for the industry density setting.

src/genworld_gui.cpp

@@ -339,6 +339,8 @@ static const StringID _num_towns[]   = {STR_NUM_VERY_LOW, STR_NUM_LOW, STR_NUM_N
 static const StringID _num_inds[]    = {STR_FUNDING_ONLY, STR_MINIMAL, STR_NUM_VERY_LOW, STR_NUM_LOW, STR_NUM_NORMAL, STR_NUM_HIGH, INVALID_STRING_ID};
 static const StringID _variety[]     = {STR_VARIETY_NONE, STR_VARIETY_VERY_LOW, STR_VARIETY_LOW, STR_VARIETY_MEDIUM, STR_VARIETY_HIGH, STR_VARIETY_VERY_HIGH, INVALID_STRING_ID};
 
+assert_compile(lengthof(_num_inds) == ID_END + 1);
+
 struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 	uint widget_id;
 	uint x;