add global_script statistics dimension property

this script is ran once at the start, and its result is stored in the 'global_value' variable, which is accessible to the regular script.

doc/type/statistics_dimension.txt

@@ -16,7 +16,8 @@ Categories are also automatically generated from dimensions.
 | @description@		[[type:localized string]]		@""@		A description of the dimension, currently not used.
 | @position hint@	[[type:string]]		@0@		Hint for ordering dimensions.
 | @icon@		[[type:filename]]	 		Filename of an icon for this dimension.
-| @script@		[[type:script]]		''required''	Script that generates a value for each card in the set.
+| @script@		[[type:script]]		''required''	Script that generates a value for each card in the set. Ran once for each card, then all the results are tallied.
+| @global_script@		[[type:script]]		''nil''	Script that is ran once at the start. Its result is stored in the 'global_value' variable, which is accessible to the regular script.
 | @numeric@		[[type:boolean]]	@false@		Is the value always a number?
 | @bin size@		[[type:double]]		''none''	For numeric dimensions: group numbers together into bins this large.<br/>
 			 			 		For example with @bin size: 5@, values @1@ and @3@ both get put under @"1-5"@.

src/data/statistics.cpp

@@ -68,6 +68,7 @@ IMPLEMENT_REFLECTION_NO_GET_MEMBER(StatsDimension) {
     REFLECT(position_hint);
     REFLECT_N("icon", icon_filename);
     REFLECT(script);
+    REFLECT(global_script);
     REFLECT(numeric);
     REFLECT(bin_size);
     REFLECT(show_empty);

src/data/statistics.hpp

@@ -27,19 +27,20 @@ public:
   StatsDimension();
   StatsDimension(const Field&);
   
-  const bool        automatic;    ///< Based on a card field?
-  String            name;        ///< Name of this dimension
-  LocalizedString   description;    ///< Description, used in status bar
-  int               position_hint;  ///< Hint for the ordering
-  String            icon_filename;  ///< Icon for lists
-  Bitmap            icon;        ///< The loaded icon (optional of course)
-  OptionalScript    script;      ///< Script that determines the value(s)
-  bool              numeric;      ///< Are the values numeric? If so, they require special sorting
+  const bool        automatic;     ///< Based on a card field?
+  String            name;          ///< Name of this dimension
+  LocalizedString   description;   ///< Description, used in status bar
+  int               position_hint; ///< Hint for the ordering
+  String            icon_filename; ///< Icon for lists
+  Bitmap            icon;          ///< The loaded icon (optional of course)
+  OptionalScript    script;        ///< Script that determines the value(s), ran on each card
+  OptionalScript    global_script; ///< Script that determines the value(s), ran only once at the start
+  bool              numeric;       ///< Are the values numeric? If so, they require special sorting
   double            bin_size;      ///< Bin adjecent numbers?
   bool              show_empty;    ///< Should "" be shown?
   bool              split_list;    ///< Split values into multiple ones separated by commas
-  map<String,Color> colors;      ///< Colors for the categories
-  vector<String>    groups;      ///< Order of the items
+  map<String,Color> colors;        ///< Colors for the categories
+  vector<String>    groups;        ///< Order of the items
   
   DECLARE_REFLECTION();
 };

src/gui/set/stats_panel.cpp

@@ -472,13 +472,29 @@ void StatsPanel::showCategory(const GraphType* prefer_layout) {
       dim->groups.empty() ? nullptr : &dim->groups
       )
     );
+  }
+  // find global_script values
+  vector<ScriptValueP> global_values;
+  Context& global_ctx = set->getContext();
+  ScriptValueP global_ctx_value = global_ctx.getVariableOpt("global_value");
+  for (size_t d = 0 ; d < dims.size() ; ++d) {
+    auto& dim = dims[d];
+    try {
+      ScriptValueP global_value = dim->global_script.invoke(global_ctx);
+      global_values.push_back(global_value);
+    } catch (ScriptError const& e) {
+      handle_error(ScriptError(e.what() + _("\n  in global script for statistics dimension '") + dim->name + _("'")));
+      global_values.push_back(script_nil);
+    }
   }
-  // find values for each card
+  // find script values for each card
   for (size_t i = 0 ; i < set->cards.size() ; ++i) {
     Context& ctx = set->getContext(set->cards[i]);
     GraphElementP e = make_intrusive<GraphElement>(i);
     bool show = true;
-    FOR_EACH(dim, dims) {
+    for (size_t d = 0 ; d < dims.size() ; ++d) {
+      auto& dim = dims[d];
+      ctx.setVariable("global_value", global_values[d]);
       try {
         String value = untag(dim->script.invoke(ctx)->toString());
         e->values.push_back(value);
@@ -497,7 +513,9 @@ void StatsPanel::showCategory(const GraphType* prefer_layout) {
       assert(e->values.size() == dims.size());
       d.elements.push_back(e);
     }
-  }
+  }
+  // restore old global value if any
+  if (global_ctx_value) global_ctx.setVariable("global_value", global_ctx_value);
   // split lists
   size_t dim_id = 0;
   FOR_EACH(dim, dims) {