Index: src/window.cpp
===================================================================
--- src/window.cpp	(revision 22729)
+++ src/window.cpp	(working copy)
@@ -813,7 +813,7 @@
 static void BringWindowToFront(Window *w);
 
 /**
- * Find a window and make it the top-window on the screen.
+ * Find a window and make it the relative top-window on the screen.
  * The window gets unshaded if it was shaded, and a white border is drawn at its edges for a brief period of time to visualize its "activation".
  * @param cls WindowClass of the window to activate
  * @param number WindowNumber of the window to activate
@@ -849,20 +849,64 @@
 }
 
 /**
- * On clicking on a window, make it the frontmost window of all. However
- * there are certain windows that always need to be on-top; these include
- * - Toolbar, Statusbar (always on)
- * - New window, Chatbar (only if open)
- * The window is marked dirty for a repaint if the window is actually moved
- * @param w window that is put into the foreground
+ * Get the z-priority for a given window. This is defined as an arbitrary integer value which is used only in
+ * comparison with other z-priority values; a window with a given z-priority will appear above other windows with
+ * a lower value, and below those with a higher one. (The ordering within z-priorities can be mixed).
+ * @param w The window to get the z-priority for
+ * @pre w->window_class != WC_INVALID
+ * @return The window's z-priority
+ */
+static inline int GetWindowZPriority(const Window *w)
+{
+	assert(w->window_class != WC_INVALID);
+
+	switch (w->window_class) {
+		case WC_ENDSCREEN:
+			return 8;
+
+		case WC_HIGHSCORE:
+			return 7;
+
+		case WC_TOOLTIPS:
+			return 6;
+
+		case WC_CONSOLE:
+			return 5;
+
+		case WC_DROPDOWN_MENU:
+			return 4;
+
+		case WC_MAIN_TOOLBAR:
+		case WC_STATUS_BAR:
+			return 3;
+
+		case WC_SAVELOAD:
+			return 2;
+
+		case WC_SEND_NETWORK_MSG:
+		case WC_NEWS_WINDOW:
+			return 1;
+
+		default:
+			return 0;
+
+		case WC_MAIN_WINDOW:
+			return -1;
+	}
+}
+
+/**
+ * On clicking on a window, make it the frontmost window of all windows with an equal
+ * or lower z-priority. The window is marked dirty for a repaint if the window is actually moved
+ * @param w window that is put into the relative foreground
  * @return pointer to the window, the same as the input pointer
  */
 static void BringWindowToFront(Window *w)
 {
 	Window *v = _z_front_window;
 
-	/* Bring the window just below the vital windows */
-	for (; v != NULL && v != w && IsVitalWindow(v); v = v->z_back) { }
+	/* Bring the window just below the windows that have a greater z-priority */
+	for (; v != NULL && v != w && (v->window_class == WC_INVALID || GetWindowZPriority(v) > GetWindowZPriority(w)); v = v->z_back) { }
 
 	if (v == NULL || w == v) return; // window is already in the right position
 
@@ -929,20 +973,14 @@
 	 * window has a text box, then take focus anyway. */
 	if (this->window_class != WC_OSK && (!EditBoxInGlobalFocus() || this->nested_root->GetWidgetOfType(WWT_EDITBOX) != NULL)) SetFocusedWindow(this);
 
-	/* Hacky way of specifying always-on-top windows. These windows are
-	 * always above other windows because they are moved below them.
-	 * status-bar is above news-window because it has been created earlier.
-	 * Also, as the chat-window is excluded from this, it will always be
-	 * the last window, thus always on top.
-	 * XXX - Yes, ugly, probably needs something like w->always_on_top flag
-	 * to implement correctly, but even then you need some kind of distinction
-	 * between on-top of chat/news and status windows, because these conflict */
+	/* Insert the window into the correct location in the z-ordering. */
 	Window *w = _z_front_window;
-	if (w != NULL && this->window_class != WC_SEND_NETWORK_MSG && this->window_class != WC_HIGHSCORE && this->window_class != WC_ENDSCREEN) {
-		if (FindWindowById(WC_MAIN_TOOLBAR, 0)     != NULL) w = w->z_back;
-		if (FindWindowById(WC_STATUS_BAR, 0)       != NULL) w = w->z_back;
-		if (FindWindowById(WC_NEWS_WINDOW, 0)      != NULL) w = w->z_back;
-		if (FindWindowByClass(WC_SEND_NETWORK_MSG) != NULL) w = w->z_back;
+	if (w != NULL) {
+		while (w != NULL && (w->window_class == WC_INVALID || GetWindowZPriority(w) > GetWindowZPriority(this))) {
+			assert(!w->z_front || w->z_front->window_class == WC_INVALID || w->window_class == WC_INVALID || 
+				GetWindowZPriority(w->z_front) >= GetWindowZPriority(w));
+			w = w->z_back;
+		}
 
 		if (w == NULL) {
 			_z_back_window->z_front = this;
@@ -1930,13 +1968,13 @@
 }
 
 /**
- * Check if a window can be made top-most window, and if so do
+ * Check if a window can be made relative top-most window, and if so do
  * it. If a window does not obscure any other windows, it will not
  * be brought to the foreground. Also if the only obscuring windows
  * are so-called system-windows, the window will not be moved.
  * The function will return false when a child window of this window is a
  * modal-popup; function returns a false and child window gets a white border
- * @param w Window to bring on-top
+ * @param w Window to bring relatively on-top
  * @return false if the window has an active modal child, true otherwise
  */
 static bool MaybeBringWindowToFront(Window *w)