From d689f4578d9eacc7a45260e7d223e7fca53f1d7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Axel=20D=C3=B6rfler?= <axeld@pinc-software.de>
Date: Wed, 13 Aug 2008 09:00:36 +0000
Subject: [PATCH] * 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    | 20 ++++++--------------
 src/servers/app/WindowList.cpp | 30 ++++++++++++++++++++++++++++++
 src/servers/app/WindowList.h   | 14 +++++++++-----
 3 files changed, 45 insertions(+), 19 deletions(-)

diff --git a/src/servers/app/Desktop.cpp b/src/servers/app/Desktop.cpp
index bdc1dddd2b..b6986fb323 100644
--- a/src/servers/app/Desktop.cpp
+++ b/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 = 0;
-
-	for (Window *window = _Windows(workspace).LastWindow(); window != NULL;
-			window = window->PreviousWindow(workspace)) {
-		count++;
-	}
+	int32 count = _Windows(workspace).Count();
 
 	// write list
 
diff --git a/src/servers/app/WindowList.cpp b/src/servers/app/WindowList.cpp
index 2fef7f2829..33c91d2ebf 100644
--- a/src/servers/app/WindowList.cpp
+++ b/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;
+}
diff --git a/src/servers/app/WindowList.h b/src/servers/app/WindowList.h
index 8459418f47..fd11f7ac78 100644
--- a/src/servers/app/WindowList.h
+++ b/src/servers/app/WindowList.h
@@ -23,14 +23,18 @@ public:
 
 			void	SetIndex(int32 index);
 			int32	Index() const { return fIndex; }
-	
-			Window*	FirstWindow() { return fFirstWindow; }
-			Window*	LastWindow() { return fLastWindow; }
-	
+
+			Window*	FirstWindow() const { return fFirstWindow; }
+			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;