--- a/engine.c	Sat Oct 07 13:58:08 2006 +0000
+++ b/engine.c	Sat Oct 07 14:30:13 2006 +0000
@@ -209,8 +209,11 @@
 	SETBIT(p->avail_railtypes, e->railtype);
 
 	e->preview_player = 0xFF;
-	InvalidateWindowClasses(WC_BUILD_VEHICLE);
-	InvalidateWindowClasses(WC_REPLACE_VEHICLE);
+	if (player == _local_player) {
+		InvalidateWindowClassesData(WC_BUILD_VEHICLE);
+		InvalidateWindowClasses(WC_BUILD_VEHICLE);
+		InvalidateWindowClasses(WC_REPLACE_VEHICLE);
+	}
 }
 
 static PlayerID GetBestPlayer(PlayerID pp)
@@ -332,6 +335,7 @@
 	}
 
 	e->flags = (e->flags & ~ENGINE_INTRODUCING) | ENGINE_AVAILABLE;
+	InvalidateWindowClassesData(WC_BUILD_VEHICLE);
 	InvalidateWindowClasses(WC_BUILD_VEHICLE);
 	InvalidateWindowClasses(WC_REPLACE_VEHICLE);
 

--- a/functions.h	Sat Oct 07 13:58:08 2006 +0000
+++ b/functions.h	Sat Oct 07 14:30:13 2006 +0000
@@ -168,6 +168,7 @@
 void InvalidateWindow(WindowClass cls, WindowNumber number);
 void InvalidateWindowWidget(WindowClass cls, WindowNumber number, byte widget_index);
 void InvalidateWindowClasses(WindowClass cls);
+void InvalidateWindowClassesData(WindowClass cls);
 void DeleteWindowById(WindowClass cls, WindowNumber number);
 void DeleteWindowByClass(WindowClass cls);
 

--- a/train_gui.c	Sat Oct 07 13:58:08 2006 +0000
+++ b/train_gui.c	Sat Oct 07 14:30:13 2006 +0000
@@ -273,7 +273,10 @@
 	SetWindowWidgetLoweredState(w, BUILD_TRAIN_WIDGET_WAGONS,  WP(w,buildtrain_d).show_engine_wagon == 2);
 	SetWindowWidgetLoweredState(w, BUILD_TRAIN_WIDGET_BOTH,    WP(w,buildtrain_d).show_engine_wagon == 3);
 
-	GenerateBuildList(&WP(w,buildtrain_d).engines, &WP(w,buildtrain_d).num_engines, &WP(w,buildtrain_d).wagons, &WP(w,buildtrain_d).num_wagons, WP(w,buildtrain_d).railtype);
+	if (WP(w,buildtrain_d).data_invalidated) {
+		GenerateBuildList(&WP(w,buildtrain_d).engines, &WP(w,buildtrain_d).num_engines, &WP(w,buildtrain_d).wagons, &WP(w,buildtrain_d).num_wagons, WP(w,buildtrain_d).railtype);
+		WP(w,buildtrain_d).data_invalidated = false;
+	}
 
 	if (HASBIT(WP(w,buildtrain_d).show_engine_wagon, 0)) scrollcount += WP(w,buildtrain_d).num_engines;
 	if (HASBIT(WP(w,buildtrain_d).show_engine_wagon, 1)) scrollcount += WP(w,buildtrain_d).num_wagons;
@@ -326,6 +329,11 @@
 			WP(w,buildtrain_d).engines = NULL;
 			WP(w,buildtrain_d).wagons  = NULL;
 			WP(w,buildtrain_d).show_engine_wagon = 3;
+			WP(w,buildtrain_d).data_invalidated  = true;
+			break;
+
+		case WE_INVALIDATE_DATA:
+			WP(w,buildtrain_d).data_invalidated = true;
 			break;
 
 		case WE_DESTROY:

--- a/window.c	Sat Oct 07 13:58:08 2006 +0000
+++ b/window.c	Sat Oct 07 14:30:13 2006 +0000
@@ -1609,12 +1609,26 @@
 	}
 }
 
+void InvalidateThisWindowData(Window *w)
+{
+	CallWindowEventNP(w, WE_INVALIDATE_DATA);
+}
+
 void InvalidateWindowData(WindowClass cls, WindowNumber number)
 {
 	Window *w;
 
 	for (w = _windows; w != _last_window; w++) {
-		if (w->window_class == cls && w->window_number == number) CallWindowEventNP(w, WE_INVALIDATE_DATA);
+		if (w->window_class == cls && w->window_number == number) InvalidateThisWindowData(w);
+	}
+}
+
+void InvalidateWindowClassesData(WindowClass cls)
+{
+	Window *w;
+
+	for (w = _windows; w != _last_window; w++) {
+		if (w->window_class == cls) InvalidateThisWindowData(w);
 	}
 }
 

--- a/window.h	Sat Oct 07 13:58:08 2006 +0000
+++ b/window.h	Sat Oct 07 14:30:13 2006 +0000
@@ -394,6 +394,7 @@
 	byte railtype;
 	byte sel_index;
 	byte show_engine_wagon;
+	bool data_invalidated;
 	EngineID sel_engine;
 	EngineID rename_engine;
 	EngineID *engines;
@@ -789,6 +790,7 @@
 void InputLoop(void);
 void UpdateWindows(void);
 void InvalidateWidget(const Window *w, byte widget_index);
+void InvalidateThisWindowData(Window *w);
 void InvalidateWindowData(WindowClass cls, WindowNumber number);
 void RaiseWindowButtons(Window *w);
 void RelocateAllWindows(int neww, int newh);