Change: Allow GS access to ScriptEventEnginePreview

src/engine.cpp

@@ -911,7 +911,10 @@ void EnginesDailyLoop()
 				 * boost that they wouldn't have gotten against other human companies. The check on
 				 * the line below is just to make AIs not notice that they have a preview if they
 				 * cannot build the vehicle. */
-				if (!IsVehicleTypeDisabled(e->type, true)) AI::NewEvent(e->preview_company, new ScriptEventEnginePreview(i));
+				if (!IsVehicleTypeDisabled(e->type, true)) {
+					AI::NewEvent(e->preview_company, new ScriptEventEnginePreview(e->preview_company, i));
+					Game::NewEvent(new ScriptEventEnginePreview(e->preview_company, i));
+				}
 				if (IsInteractiveCompany(e->preview_company)) ShowEnginePreviewWindow(i);
 			}
 		}

src/script/api/game_changelog.hpp

@@ -72,6 +72,7 @@
  * \li GSGroupList
  * \li GSVehicleList_Group
  * \li GSVehicleList_DefaultGroup
+ * \li GSEventEnginePreview
  * \li GSEventCompanyAskMerger
  * \li GSEventVehicleLost
  * \li GSEventVehicleWaitingInDepot

src/script/api/script_event_types.cpp

@@ -111,6 +111,7 @@ int32 ScriptEventEnginePreview::GetVehicleType()
 
 bool ScriptEventEnginePreview::AcceptPreview()
 {
+	EnforcePrecondition(false, ScriptObject::GetCompany() == (::CompanyID)this->owner);
 	if (!this->IsEngineValid()) return false;
 	return ScriptObject::Command<CMD_WANT_ENGINE_PREVIEW>::Do(this->engine);
 }

src/script/api/script_event_types.hpp

@@ -214,16 +214,18 @@ class ScriptEventSubsidyExpired : public ScriptEvent {
  * Event Engine Preview, indicating a manufacturer offer you to test a new engine.
  *  You can get the same information about the offered engine as a real user
  *  would see in the offer window. And you can also accept the offer.
- * @api ai
+ * @api ai game
  */
 class ScriptEventEnginePreview : public ScriptEvent {
 public:
 #ifndef DOXYGEN_API
 	/**
+	 * @param owner The company being offered the test engine.
 	 * @param engine The engine offered to test.
 	 */
-	ScriptEventEnginePreview(EngineID engine) :
+	ScriptEventEnginePreview(Owner owner, EngineID engine) :
 		ScriptEvent(ET_ENGINE_PREVIEW),
+		owner((ScriptCompany::CompanyID)owner),
 		engine(engine)
 	{}
 #endif /* DOXYGEN_API */
@@ -235,6 +237,13 @@ class ScriptEventEnginePreview : public ScriptEvent {
 	 */
 	static ScriptEventEnginePreview *Convert(ScriptEvent *instance) { return (ScriptEventEnginePreview *)instance; }
 
+	/**
+	 * Get the company being offered the test engine.
+	 * @return The company being offered to test the engine.
+	 * @api -ai
+	 */
+	ScriptCompany::CompanyID GetCompanyID() { return this->owner; }
+
 	/**
 	 * Get the name of the offered engine.
 	 * @return The name the engine has.
@@ -290,11 +299,13 @@ class ScriptEventEnginePreview : public ScriptEvent {
 	/**
 	 * Accept the engine preview.
 	 * @return True when the accepting succeeded.
+	 * @game @pre Valid ScriptCompanyMode active in scope.
 	 */
 	bool AcceptPreview();
 
 private:
-	EngineID engine; ///< The engine the preview is for.
+	ScriptCompany::CompanyID owner; ///< The company the engine preview is for.
+	EngineID engine;                ///< The engine the preview is for.
 
 	/**
 	 * Check whether the engine from this preview is still valid.