* Fixed a possible deadlock in Desktop::_ActivateApp(): since ActivateWindow()

will need to write lock the window lock, we cannot call it with the read
  lock held.
* Added a TODO comment in _ActivateApp() on how we could handle minimized
  windows.
* Added a WindowList::Count() method.
* Added a WindowList::ValidateWindow() that you can use to validate a window
  pointer in case you had to unlock the list.
* Made FirstWindow()/LastWindow() const.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@26957 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/app/Desktop.cpp

@@ -669,24 +669,19 @@ Desktop::_ActivateApp(team_id team)
 {
 	// search for an unhidden window in the current workspace
 
-	LockSingleWindow();
+	AutoWriteLocker locker(fWindowLock);
 
 	for (Window* window = _CurrentWindows().LastWindow(); window != NULL;
 			window = window->PreviousWindow(fCurrentWorkspace)) {
 		if (!window->IsHidden() && window->IsNormal()
 			&& window->ServerWindow()->ClientTeam() == team) {
 			ActivateWindow(window);
-			UnlockSingleWindow();
 			return B_OK;
 		}
 	}
 
-	UnlockSingleWindow();
-
 	// search for an unhidden window to give focus to
 
-	AutoWriteLocker locker(fWindowLock);
-
 	for (Window* window = fAllWindows.FirstWindow(); window != NULL;
 			window = window->NextWindow(kAllWindowList)) {
 		// if window is a normal window of the team, and not hidden,
@@ -698,6 +693,10 @@ Desktop::_ActivateApp(team_id team)
 		}
 	}
 
+	// TODO: we cannot maximize minimized windows here (with the window lock
+	// write locked). To work-around this, we could forward the request to
+	// the ServerApp of this team - it maintains its own window list, and can
+	// therefore call ActivateWindow() without holding the window lock.
 	return B_BAD_VALUE;
 }
 
@@ -2505,14 +2504,7 @@ Desktop::WriteWindowOrder(int32 workspace, BPrivate::LinkSender& sender)
 		return;
 	}
 
-	// compute the number of windows
+	int32 count = _Windows(workspace).Count();
-
-	int32 count = 0;
-
-	for (Window *window = _Windows(workspace).LastWindow(); window != NULL;
-			window = window->PreviousWindow(workspace)) {
-		count++;
-	}
 
 	// write list
 

src/servers/app/WindowList.cpp

@@ -128,3 +128,33 @@ WindowList::HasWindow(Window* window) const
 		|| fLastWindow == window;
 }
 
+
+/*!	Unlike HasWindow(), this will not reference the window pointer. You
+	can use this method to check whether or not a window is still part
+	of a list (when it's possible that the window is already gone).
+*/
+bool
+WindowList::ValidateWindow(Window* validateWindow) const
+{
+	for (Window *window = FirstWindow(); window != NULL;
+			window = window->NextWindow(fIndex)) {
+		if (window == validateWindow)
+			return true;
+	}
+
+	return false;
+}
+
+
+int32
+WindowList::Count() const
+{
+	int32 count = 0;
+
+	for (Window *window = FirstWindow(); window != NULL;
+			window = window->NextWindow(fIndex)) {
+		count++;
+	}
+
+	return count;
+}

src/servers/app/WindowList.h

@@ -24,13 +24,17 @@ public:
 			void	SetIndex(int32 index);
 			int32	Index() const { return fIndex; }
 
-			Window*	FirstWindow() { return fFirstWindow; }
+			Window*	FirstWindow() const { return fFirstWindow; }
-			Window*	LastWindow() { return fLastWindow; }
+			Window*	LastWindow() const { return fLastWindow; }
 
 			void	AddWindow(Window* window, Window* before = NULL);
 			void	RemoveWindow(Window* window);
 
 			bool	HasWindow(Window* window) const;
+			bool	ValidateWindow(Window* window) const;
+
+			int32	Count() const;
+						// O(n)
 
 private:
 	int32			fIndex;