diff --git a/src/misc_gui.cpp b/src/misc_gui.cpp
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@@ -1158,11 +1158,11 @@ bool QueryString::HasEditBoxFocus(const 
 	return w->parent->nested_focus != NULL && w->parent->nested_focus->type == WWT_EDITBOX;
 }
 
-HandleEditBoxResult QueryString::HandleEditBoxKey(Window *w, int wid, uint16 key, uint16 keycode, Window::EventState &state)
+HandleEditBoxResult QueryString::HandleEditBoxKey(Window *w, int wid, uint16 key, uint16 keycode, EventState &state)
 {
 	if (!QueryString::HasEditBoxFocus(w, wid)) return HEBR_NOT_FOCUSED;
 
-	state = Window::ES_HANDLED;
+	state = ES_HANDLED;
 
 	switch (keycode) {
 		case WKC_ESC: return HEBR_CANCEL;
@@ -1196,7 +1196,7 @@ HandleEditBoxResult QueryString::HandleE
 			if (IsValidChar(key, this->afilter)) {
 				if (InsertTextBufferChar(&this->text, key)) w->SetWidgetDirty(wid);
 			} else {
-				state = Window::ES_NOT_HANDLED;
+				state = ES_NOT_HANDLED;
 			}
 	}
 
diff --git a/src/querystring_gui.h b/src/querystring_gui.h
--- a/src/querystring_gui.h
+++ b/src/querystring_gui.h
@@ -56,7 +56,7 @@ private:
 public:
 	void DrawEditBox(Window *w, int wid);
 	void HandleEditBox(Window *w, int wid);
-	HandleEditBoxResult HandleEditBoxKey(Window *w, int wid, uint16 key, uint16 keycode, Window::EventState &state);
+	HandleEditBoxResult HandleEditBoxKey(Window *w, int wid, uint16 key, uint16 keycode, EventState &state);
 };
 
 struct QueryStringBaseWindow : public Window, public QueryString {
diff --git a/src/window.cpp b/src/window.cpp
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -1938,14 +1938,14 @@ void HandleKeypress(uint32 raw_key)
 	/* Check if the focused window has a focused editbox */
 	if (EditBoxInGlobalFocus()) {
 		/* All input will in this case go to the focused window */
-		if (_focused_window->OnKeyPress(key, keycode) == Window::ES_HANDLED) return;
+		if (_focused_window->OnKeyPress(key, keycode) == ES_HANDLED) return;
 	}
 
 	/* Call the event, start with the uppermost window, but ignore the toolbar. */
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) {
 		if (w->window_class == WC_MAIN_TOOLBAR) continue;
-		if (w->OnKeyPress(key, keycode) == Window::ES_HANDLED) return;
+		if (w->OnKeyPress(key, keycode) == ES_HANDLED) return;
 	}
 
 	w = FindWindowById(WC_MAIN_TOOLBAR, 0);
@@ -1961,7 +1961,7 @@ void HandleCtrlChanged()
 	/* Call the event, start with the uppermost window. */
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) {
-		if (w->OnCTRLStateChange() == Window::ES_HANDLED) return;
+		if (w->OnCTRLStateChange() == ES_HANDLED) return;
 	}
 }
 
diff --git a/src/window_gui.h b/src/window_gui.h
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -19,6 +19,12 @@
 #include "tile_type.h"
 #include "widget_type.h"
 
+/** State of handling an event. */
+enum EventState {
+	ES_HANDLED,     ///< The passed event is handled.
+	ES_NOT_HANDLED, ///< The passed event is not handled.
+};
+
 /**
  * Flags to describe the look of the frame
  */
@@ -334,12 +340,6 @@ struct ViewportData : ViewPort {
  * Data structure for an opened window
  */
 struct Window : ZeroedMemoryAllocator {
-	/** State whether an event is handled or not */
-	enum EventState {
-		ES_HANDLED,     ///< The passed event is handled
-		ES_NOT_HANDLED, ///< The passed event is not handled
-	};
-
 protected:
 	void InitializeData(const WindowDesc *desc, WindowNumber window_number);
 	void InitializePositionSize(int x, int y, int min_width, int min_height);