Changed the way DesktopSettings work:

* Removed the DesktopSettings lock itself - it's not really needed at all,
  and causes some trouble with a clean locking design. This may even have
  fixed bug #757, at least I couldn't reproduce it anymore.
* There is now a class for read-only access that requires you to have locked
  the desktop (either read or write).
* There is now another class LockedDesktopSettings that allows you to set
  settings (and only that) - when you're changing the settings, you must not
  have read locked the desktop (ie. hold the single window lock). The class
  will obtain a write lock, but write locks can be nested.
* Moved SetWorkspacesCount() into the Desktop class.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@18646 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/app/DecorManager.cpp

@@ -74,6 +74,9 @@ Decorator *
 DecorInfo::Instantiate(Desktop* desktop, BRect rect, const char *title,
 	window_look look, uint32 flags)
 {
+	if (desktop->LockSingleWindow() == NULL)
+		return NULL;
+
 	DesktopSettings settings(desktop);
 	Decorator *decorator;
 	
@@ -83,9 +86,12 @@ DecorInfo::Instantiate(Desktop* desktop, BRect rect, const char *title,
 		else
 			decorator = new DefaultDecorator(settings, rect, look, flags);
 	} catch (...) {
+		desktop->UnlockSingleWindow();
 		return NULL;
 	}
 
+	desktop->UnlockSingleWindow();
+
 	decorator->SetDriver(desktop->GetDrawingEngine());
 	decorator->SetTitle(title);
 

src/servers/app/Desktop.cpp

@@ -349,7 +349,7 @@ Desktop::Init()
 	if (fSharedReadOnlyArea < B_OK)
 		return fSharedReadOnlyArea;
 
-	fSettings = new DesktopSettings::Private(fServerReadOnlyMemory);
+	fSettings = new DesktopSettingsPrivate(fServerReadOnlyMemory);
 
 	for (int32 i = 0; i < kMaxWorkspaces; i++) {
 		_Windows(i).SetIndex(i);
@@ -717,15 +717,39 @@ Desktop::StoreWorkspaceConfiguration(int32 index)
 }
 
 
-void
+status_t
-Desktop::UpdateWorkspaces()
+Desktop::SetWorkspacesCount(int32 newCount)
 {
-	// TODO: maybe this should be replaced by a SetWorkspacesCount() method
+	if (newCount < 1 || newCount > kMaxWorkspaces)
+		return B_BAD_VALUE;
 
-	_WindowChanged(NULL);
+	if (!LockAllWindows())
+		return B_ERROR;
+
+	fSettings->SetWorkspacesCount(newCount);
+
+	// either update the workspaces window, or switch to
+	// the last available workspace - which will update
+	// the workspaces window automatically
+	bool workspaceChanged = CurrentWorkspace() >= newCount;
+	if (workspaceChanged)
+		_SetWorkspace(newCount - 1);
+	else
+		_WindowChanged(NULL);
+
+	UnlockAllWindows();
+
+	if (workspaceChanged)
+		_SendFakeMouseMoved();
+
+	return B_OK;
 }
 
 
+/*!
+	Changes the current workspace to the one specified by \a index.
+	You must not hold any window lock when calling this method.
+*/
 void
 Desktop::SetWorkspace(int32 index)
 {
@@ -737,6 +761,20 @@ Desktop::SetWorkspace(int32 index)
 		return;
 	}
 
+	_SetWorkspace(index);
+	UnlockAllWindows();
+
+	_SendFakeMouseMoved();
+}
+
+
+/*!
+	Changes the current workspace to the one specified by \a index.
+	You must hold the all window lock when calling this method.
+*/
+void
+Desktop::_SetWorkspace(int32 index)
+{
 	int32 previousIndex = fCurrentWorkspace;
 	RGBColor previousColor = fWorkspaces[fCurrentWorkspace].Color();
 	bool movedMouseEventWindow = false;
@@ -864,10 +902,6 @@ Desktop::SetWorkspace(int32 index)
 
 	if (previousColor != fWorkspaces[fCurrentWorkspace].Color())
 		RedrawBackground();
-
-	UnlockAllWindows();
-
-	_SendFakeMouseMoved();
 }
 
 
@@ -1056,6 +1090,9 @@ Desktop::_WindowHasModal(WindowLayer* window)
 }
 
 
+/*!
+	You must at least hold a single window lock when calling this method.
+*/
 void
 Desktop::_WindowChanged(WindowLayer* window)
 {

src/servers/app/Desktop.h

@@ -97,7 +97,7 @@ class Desktop : public MessageLooper, public ScreenOwner {
 									{ return fCurrentWorkspace; }
 		Workspace::Private&		WorkspaceAt(int32 index)
 									{ return fWorkspaces[index]; }
-		void					UpdateWorkspaces();
+		status_t				SetWorkspacesCount(int32 newCount);
 
 		// WindowLayer methods
 
@@ -180,6 +180,7 @@ class Desktop : public MessageLooper, public ScreenOwner {
 									BPrivate::LinkSender& sender);
 
 	private:
+		void					_SetWorkspace(int32 index);
 		void					_ShowWindow(WindowLayer* window,
 									bool affectsOtherWindows = true);
 		void					_HideWindow(WindowLayer* window);
@@ -218,10 +219,11 @@ class Desktop : public MessageLooper, public ScreenOwner {
 
 	private:
 		friend class DesktopSettings;
+		friend class LockedDesktopSettings;
 
 		uid_t					fUserID;
 		::VirtualScreen			fVirtualScreen;
-		DesktopSettings::Private* fSettings;
+		DesktopSettingsPrivate*	fSettings;
 		port_id					fMessagePort;
 		::EventDispatcher		fEventDispatcher;
 		port_id					fInputPort;

src/servers/app/DesktopSettings.cpp

@@ -23,8 +23,8 @@
 #include <Path.h>
 
 
-DesktopSettings::Private::Private(server_read_only_memory* shared)
+DesktopSettingsPrivate::DesktopSettingsPrivate(server_read_only_memory* shared)
-	: BLocker("DesktopSettings_Private"),
+	:
 	fShared(*shared)
 {
 	// if the on-disk settings are not complete, the defaults will be kept
@@ -33,13 +33,13 @@ DesktopSettings::Private::Private(server_read_only_memory* shared)
 }
 
 
-DesktopSettings::Private::~Private()
+DesktopSettingsPrivate::~DesktopSettingsPrivate()
 {
 }
 
 
 void
-DesktopSettings::Private::_SetDefaults()
+DesktopSettingsPrivate::_SetDefaults()
 {
 	fPlainFont = *gFontManager->DefaultPlainFont();
 	fBoldFont = *gFontManager->DefaultBoldFont();
@@ -73,7 +73,7 @@ DesktopSettings::Private::_SetDefaults()
 
 
 status_t
-DesktopSettings::Private::_GetPath(BPath& path)
+DesktopSettingsPrivate::_GetPath(BPath& path)
 {
 	status_t status = find_directory(B_USER_SETTINGS_DIRECTORY, &path);
 	if (status < B_OK)
@@ -88,7 +88,7 @@ DesktopSettings::Private::_GetPath(BPath& path)
 
 
 status_t
-DesktopSettings::Private::_Load()
+DesktopSettingsPrivate::_Load()
 {
 	// TODO: add support for old app_server_settings file as well
 
@@ -224,7 +224,7 @@ DesktopSettings::Private::_Load()
 
 
 status_t
-DesktopSettings::Private::Save(uint32 mask)
+DesktopSettingsPrivate::Save(uint32 mask)
 {
 	BPath basePath;
 	status_t status = _GetPath(basePath);
@@ -314,7 +314,7 @@ DesktopSettings::Private::Save(uint32 mask)
 
 
 void
-DesktopSettings::Private::SetDefaultPlainFont(const ServerFont &font)
+DesktopSettingsPrivate::SetDefaultPlainFont(const ServerFont &font)
 {
 	fPlainFont = font;
 	Save(kFontSettings);
@@ -322,14 +322,14 @@ DesktopSettings::Private::SetDefaultPlainFont(const ServerFont &font)
 
 
 const ServerFont &
-DesktopSettings::Private::DefaultPlainFont() const
+DesktopSettingsPrivate::DefaultPlainFont() const
 {
 	return fPlainFont;
 }
 
 
 void
-DesktopSettings::Private::SetDefaultBoldFont(const ServerFont &font)
+DesktopSettingsPrivate::SetDefaultBoldFont(const ServerFont &font)
 {
 	fBoldFont = font;
 	Save(kFontSettings);
@@ -337,14 +337,14 @@ DesktopSettings::Private::SetDefaultBoldFont(const ServerFont &font)
 
 
 const ServerFont &
-DesktopSettings::Private::DefaultBoldFont() const
+DesktopSettingsPrivate::DefaultBoldFont() const
 {
 	return fBoldFont;
 }
 
 
 void
-DesktopSettings::Private::SetDefaultFixedFont(const ServerFont &font)
+DesktopSettingsPrivate::SetDefaultFixedFont(const ServerFont &font)
 {
 	fFixedFont = font;
 	Save(kFontSettings);
@@ -352,14 +352,14 @@ DesktopSettings::Private::SetDefaultFixedFont(const ServerFont &font)
 
 
 const ServerFont &
-DesktopSettings::Private::DefaultFixedFont() const
+DesktopSettingsPrivate::DefaultFixedFont() const
 {
 	return fFixedFont;
 }
 
 
 void
-DesktopSettings::Private::SetScrollBarInfo(const scroll_bar_info& info)
+DesktopSettingsPrivate::SetScrollBarInfo(const scroll_bar_info& info)
 {
 	fScrollBarInfo = info;
 	Save(kAppearanceSettings);
@@ -367,14 +367,14 @@ DesktopSettings::Private::SetScrollBarInfo(const scroll_bar_info& info)
 
 
 const scroll_bar_info&
-DesktopSettings::Private::ScrollBarInfo() const
+DesktopSettingsPrivate::ScrollBarInfo() const
 {
 	return fScrollBarInfo;
 }
 
 
 void
-DesktopSettings::Private::SetMenuInfo(const menu_info& info)
+DesktopSettingsPrivate::SetMenuInfo(const menu_info& info)
 {
 	fMenuInfo = info;
 	Save(kAppearanceSettings);
@@ -382,14 +382,14 @@ DesktopSettings::Private::SetMenuInfo(const menu_info& info)
 
 
 const menu_info&
-DesktopSettings::Private::MenuInfo() const
+DesktopSettingsPrivate::MenuInfo() const
 {
 	return fMenuInfo;
 }
 
 
 void
-DesktopSettings::Private::SetMouseMode(const mode_mouse mode)
+DesktopSettingsPrivate::SetMouseMode(const mode_mouse mode)
 {
 	fMouseMode = mode;
 	Save(kMouseSettings);
@@ -397,21 +397,21 @@ DesktopSettings::Private::SetMouseMode(const mode_mouse mode)
 
 
 mode_mouse
-DesktopSettings::Private::MouseMode() const
+DesktopSettingsPrivate::MouseMode() const
 {
 	return fMouseMode;
 }
 
 
 bool
-DesktopSettings::Private::FocusFollowsMouse() const
+DesktopSettingsPrivate::FocusFollowsMouse() const
 {
 	return MouseMode() != B_NORMAL_MOUSE;
 }
 
 
 void
-DesktopSettings::Private::SetWorkspacesCount(int32 number)
+DesktopSettingsPrivate::SetWorkspacesCount(int32 number)
 {
 	if (number < 1)
 		number = 1;
@@ -423,14 +423,14 @@ DesktopSettings::Private::SetWorkspacesCount(int32 number)
 
 
 int32
-DesktopSettings::Private::WorkspacesCount() const
+DesktopSettingsPrivate::WorkspacesCount() const
 {
 	return fWorkspacesCount;
 }
 
 
 void
-DesktopSettings::Private::SetWorkspacesMessage(int32 index, BMessage& message)
+DesktopSettingsPrivate::SetWorkspacesMessage(int32 index, BMessage& message)
 {
 	if (index < 0 || index > kMaxWorkspaces)
 		return;
@@ -440,7 +440,7 @@ DesktopSettings::Private::SetWorkspacesMessage(int32 index, BMessage& message)
 
 
 const BMessage*
-DesktopSettings::Private::WorkspacesMessage(int32 index) const
+DesktopSettingsPrivate::WorkspacesMessage(int32 index) const
 {
 	if (index < 0 || index > kMaxWorkspaces)
 		return NULL;
@@ -449,27 +449,15 @@ DesktopSettings::Private::WorkspacesMessage(int32 index) const
 }
 
 
-
+//	#pragma mark - read access
-//	#pragma mark -
 
 
 DesktopSettings::DesktopSettings(Desktop* desktop)
+	:
+	fSettings(desktop->fSettings)
 {
-	fSettings = desktop->fSettings;
+	if (!desktop->fWindowLock.IsReadLocked() && !desktop->fWindowLock.IsWriteLocked())
-	fSettings->Lock();
+		debugger("desktop not locked when trying to access settings");
-}
-
-
-DesktopSettings::~DesktopSettings()
-{
-	fSettings->Unlock();
-}
-
-
-void
-DesktopSettings::SetDefaultPlainFont(const ServerFont &font)
-{
-	fSettings->SetDefaultPlainFont(font);
 }
 
 
@@ -480,13 +468,6 @@ DesktopSettings::GetDefaultPlainFont(ServerFont &font) const
 }
 
 
-void
-DesktopSettings::SetDefaultBoldFont(const ServerFont &font)
-{
-	fSettings->SetDefaultBoldFont(font);
-}
-
-
 void
 DesktopSettings::GetDefaultBoldFont(ServerFont &font) const
 {
@@ -494,13 +475,6 @@ DesktopSettings::GetDefaultBoldFont(ServerFont &font) const
 }
 
 
-void
-DesktopSettings::SetDefaultFixedFont(const ServerFont &font)
-{
-	fSettings->SetDefaultFixedFont(font);
-}
-
-
 void
 DesktopSettings::GetDefaultFixedFont(ServerFont &font) const
 {
@@ -508,13 +482,6 @@ DesktopSettings::GetDefaultFixedFont(ServerFont &font) const
 }
 
 
-void
-DesktopSettings::SetScrollBarInfo(const scroll_bar_info& info)
-{
-	fSettings->SetScrollBarInfo(info);
-}
-
-
 void
 DesktopSettings::GetScrollBarInfo(scroll_bar_info& info) const
 {
@@ -522,13 +489,6 @@ DesktopSettings::GetScrollBarInfo(scroll_bar_info& info) const
 }
 
 
-void
-DesktopSettings::SetMenuInfo(const menu_info& info)
-{
-	fSettings->SetMenuInfo(info);
-}
-
-
 void
 DesktopSettings::GetMenuInfo(menu_info& info) const
 {
@@ -536,13 +496,6 @@ DesktopSettings::GetMenuInfo(menu_info& info) const
 }
 
 
-void
-DesktopSettings::SetMouseMode(const mode_mouse mode)
-{
-	fSettings->SetMouseMode(mode);
-}
-
-
 mode_mouse
 DesktopSettings::MouseMode() const
 {
@@ -557,13 +510,6 @@ DesktopSettings::FocusFollowsMouse() const
 }
 
 
-void
-DesktopSettings::SetWorkspacesCount(int32 number)
-{
-	fSettings->SetWorkspacesCount(number);
-}
-
-
 int32
 DesktopSettings::WorkspacesCount() const
 {
@@ -571,16 +517,76 @@ DesktopSettings::WorkspacesCount() const
 }
 
 
-void
-DesktopSettings::SetWorkspacesMessage(int32 index, BMessage& message)
-{
-	fSettings->SetWorkspacesMessage(index, message);
-}
-
-
 const BMessage*
 DesktopSettings::WorkspacesMessage(int32 index) const
 {
 	return fSettings->WorkspacesMessage(index);
 }
 
+
+//	#pragma mark - write access
+
+
+LockedDesktopSettings::LockedDesktopSettings(Desktop* desktop)
+	:
+	fSettings(desktop->fSettings),
+	fDesktop(desktop)
+{
+	// TODO: this only works in MultiLocker's DEBUG mode
+#if 0
+	if (desktop->fWindowLock.IsReadLocked())
+		debugger("desktop read locked when trying to change settings");
+#endif
+
+	fDesktop->LockAllWindows();
+}
+
+
+LockedDesktopSettings::~LockedDesktopSettings()
+{
+	fDesktop->UnlockAllWindows();
+}
+
+
+void
+LockedDesktopSettings::SetDefaultPlainFont(const ServerFont &font)
+{
+	fSettings->SetDefaultPlainFont(font);
+}
+
+
+void
+LockedDesktopSettings::SetDefaultBoldFont(const ServerFont &font)
+{
+	fSettings->SetDefaultBoldFont(font);
+}
+
+
+void
+LockedDesktopSettings::SetDefaultFixedFont(const ServerFont &font)
+{
+	fSettings->SetDefaultFixedFont(font);
+}
+
+
+void
+LockedDesktopSettings::SetScrollBarInfo(const scroll_bar_info& info)
+{
+	fSettings->SetScrollBarInfo(info);
+}
+
+
+void
+LockedDesktopSettings::SetMenuInfo(const menu_info& info)
+{
+	fSettings->SetMenuInfo(info);
+}
+
+
+void
+LockedDesktopSettings::SetMouseMode(const mode_mouse mode)
+{
+	fSettings->SetMouseMode(mode);
+}
+
+

src/servers/app/DesktopSettings.h

@@ -14,6 +14,7 @@
 #include <Message.h>
 
 class Desktop;
+class DesktopSettingsPrivate;
 class ServerFont;
 
 
@@ -30,40 +31,47 @@ enum {
 class DesktopSettings {
 	public:
 		DesktopSettings(Desktop* desktop);
-		~DesktopSettings();
 
 		status_t		Save(uint32 mask = kAllSettings);
 
-		void			SetDefaultPlainFont(const ServerFont& font);
 		void			GetDefaultPlainFont(ServerFont& font) const;
-
-		void			SetDefaultBoldFont(const ServerFont& font);
 		void			GetDefaultBoldFont(ServerFont& font) const;
-
-		void			SetDefaultFixedFont(const ServerFont& font);
 		void			GetDefaultFixedFont(ServerFont& font) const;
 
-		void			SetScrollBarInfo(const scroll_bar_info& info);
 		void			GetScrollBarInfo(scroll_bar_info& info) const;
-
-		void			SetMenuInfo(const menu_info& info);
 		void			GetMenuInfo(menu_info& info) const;
 
-		void			SetMouseMode(mode_mouse mode);
 		mode_mouse		MouseMode() const;
 		bool			FocusFollowsMouse() const;
 
-		void			SetWorkspacesCount(int32 number);
 		int32			WorkspacesCount() const;
-
-		void			SetWorkspacesMessage(int32 index, BMessage& message);
 		const BMessage*	WorkspacesMessage(int32 index) const;
 
 	private:
-		class Private;
+//		friend class Desktop;
-		friend class Desktop;
 
-		Private*		fSettings;
+		DesktopSettingsPrivate*	fSettings;
+};
+
+class LockedDesktopSettings {
+	public:
+		LockedDesktopSettings(Desktop* desktop);
+		~LockedDesktopSettings();
+
+		void			SetDefaultPlainFont(const ServerFont& font);
+		void			SetDefaultBoldFont(const ServerFont& font);
+		void			SetDefaultFixedFont(const ServerFont& font);
+
+		void			SetScrollBarInfo(const scroll_bar_info& info);
+		void			SetMenuInfo(const menu_info& info);
+
+		void			SetMouseMode(mode_mouse mode);
+
+	private:
+//		friend class Desktop;
+
+		DesktopSettingsPrivate*	fSettings;
+		Desktop*		fDesktop;
 };
 
 #endif	/* DESKTOP_SETTINGS_H */

src/servers/app/DesktopSettingsPrivate.h

@@ -17,10 +17,10 @@
 struct server_read_only_memory;
 
 
-class DesktopSettings::Private : public BLocker {
+class DesktopSettingsPrivate {
 	public:
-		Private(server_read_only_memory* shared);
+		DesktopSettingsPrivate(server_read_only_memory* shared);
-		~Private();
+		~DesktopSettingsPrivate();
 
 		status_t		Save(uint32 mask = kAllSettings);
 

src/servers/app/ServerApp.cpp

@@ -757,30 +757,24 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 
 		case AS_COUNT_WORKSPACES:
 		{
-			DesktopSettings settings(fDesktop);
+			if (fDesktop->LockSingleWindow()) {
+				DesktopSettings settings(fDesktop);
+
+				fLink.StartMessage(B_OK);
+				fLink.Attach<int32>(settings.WorkspacesCount());
+				fDesktop->UnlockSingleWindow();
+			} else
+				fLink.StartMessage(B_ERROR);
 
-			fLink.StartMessage(B_OK);
-			fLink.Attach<int32>(settings.WorkspacesCount());
 			fLink.Flush();
 			break;
 		}
 
 		case AS_SET_WORKSPACE_COUNT:
 		{
-			DesktopSettings settings(fDesktop);
-
 			int32 newCount;
-			if (link.Read<int32>(&newCount) == B_OK) {
+			if (link.Read<int32>(&newCount) == B_OK)
-				settings.SetWorkspacesCount(newCount);
+				fDesktop->SetWorkspacesCount(newCount);
-
-				// either update the workspaces window, or switch to
-				// the last available workspace - which will update
-				// the workspaces window automatically
-				if (fDesktop->CurrentWorkspace() >= newCount)
-					fDesktop->SetWorkspace(newCount - 1);
-				else
-					fDesktop->UpdateWorkspaces();
-			}
 			break;
 		}
 
@@ -795,7 +789,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 		case AS_ACTIVATE_WORKSPACE:
 		{
 			STRACE(("ServerApp %s: activate workspace\n", Signature()));
-			
+
 			// TODO: See above
 			int32 index;
 			link.Read<int32>(&index);
@@ -944,13 +938,19 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 		case AS_GET_SCROLLBAR_INFO:
 		{
 			STRACE(("ServerApp %s: Get ScrollBar info\n", Signature()));
-			scroll_bar_info info;
+			
-			DesktopSettings settings(fDesktop);
+			if (fDesktop->LockSingleWindow()) {
-			settings.GetScrollBarInfo(info);
+				scroll_bar_info info;
+				DesktopSettings settings(fDesktop);
+				settings.GetScrollBarInfo(info);
 
-			fLink.StartMessage(B_OK);
+				fLink.StartMessage(B_OK);
-			fLink.Attach<scroll_bar_info>(info);
+				fLink.Attach<scroll_bar_info>(info);
-			fLink.Flush();
+				fDesktop->UnlockSingleWindow();
+			} else
+				fLink.StartMessage(B_ERROR);
+
+				fLink.Flush();
 			break;
 		}
 		case AS_SET_SCROLLBAR_INFO:
@@ -960,7 +960,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			// 1) scroll_bar_info scroll bar info structure
 			scroll_bar_info info;
 			if (link.Read<scroll_bar_info>(&info) == B_OK) {
-				DesktopSettings settings(fDesktop);
+				LockedDesktopSettings settings(fDesktop);
 				settings.SetScrollBarInfo(info);
 			}
 
@@ -972,12 +972,18 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 		case AS_GET_MENU_INFO:
 		{
 			STRACE(("ServerApp %s: Get menu info\n", Signature()));
-			menu_info info;
+			if (fDesktop->LockSingleWindow()) {
-			DesktopSettings settings(fDesktop);
+				menu_info info;
-			settings.GetMenuInfo(info);
+				DesktopSettings settings(fDesktop);
+				settings.GetMenuInfo(info);
+
+				fLink.StartMessage(B_OK);
+				fLink.Attach<menu_info>(info);
+
+				fDesktop->UnlockSingleWindow();
+			} else
+				fLink.StartMessage(B_ERROR);
 
-			fLink.StartMessage(B_OK);
-			fLink.Attach<menu_info>(info);
 			fLink.Flush();
 			break;
 		}
@@ -986,7 +992,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			STRACE(("ServerApp %s: Set menu info\n", Signature()));
 			menu_info info;
 			if (link.Read<menu_info>(&info) == B_OK) {
-				DesktopSettings settings(fDesktop);
+				LockedDesktopSettings settings(fDesktop);
 				settings.SetMenuInfo(info);
 					// TODO: SetMenuInfo() should do some validity check, so
 					//	that the answer we're giving can actually be useful
@@ -1004,7 +1010,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			// 1) enum mode_mouse FFM mouse mode
 			mode_mouse mouseMode;
 			if (link.Read<mode_mouse>(&mouseMode) == B_OK) {
-				DesktopSettings settings(fDesktop);
+				LockedDesktopSettings settings(fDesktop);
 				settings.SetMouseMode(mouseMode);
 			}
 			break;
@@ -1012,10 +1018,17 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 		case AS_GET_MOUSE_MODE:
 		{
 			STRACE(("ServerApp %s: Get Focus Follows Mouse mode\n", Signature()));
-			DesktopSettings settings(fDesktop);
+			
+			if (fDesktop->LockSingleWindow()) {
+				DesktopSettings settings(fDesktop);
+
+				fLink.StartMessage(B_OK);
+				fLink.Attach<mode_mouse>(settings.MouseMode());
+
+				fDesktop->UnlockSingleWindow();
+			} else
+				fLink.StartMessage(B_ERROR);
 
-			fLink.StartMessage(B_OK);
-			fLink.Attach<mode_mouse>(settings.MouseMode());
 			fLink.Flush();
 			break;
 		}
@@ -1044,7 +1057,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 				FontStyle* style = gFontManager->GetStyle(familyName, styleName);
 				if (style != NULL) {
 					ServerFont font(*style, size);
-					DesktopSettings settings(fDesktop);
+					LockedDesktopSettings settings(fDesktop);
 
 					if (!strcmp(type, "plain"))
 						settings.SetDefaultPlainFont(font);
@@ -1102,6 +1115,12 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			// 4) uint16 - face flags
 			// 5) uint32 - font flags
 
+			if (!fDesktop->LockSingleWindow()) {
+				fLink.StartMessage(B_OK);
+				fLink.Flush();
+				break;
+			}
+
 			DesktopSettings settings(fDesktop);
 			fLink.StartMessage(B_OK);
 
@@ -1129,6 +1148,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 				fLink.Attach<uint32>(font.Flags());
 			}
 
+			fDesktop->UnlockSingleWindow();
 			fLink.Flush();
 			break;
 		}