* implemented infrastructure for undo/redo of playlist operations,

everything regarding playlist modification is now tunneled through
  the playlist window


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@21312 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/apps/mediaplayer/Jamfile

@@ -7,6 +7,7 @@ AddSubDirSupportedPlatforms libbe_test ;
 # source directories
 local sourceDirs =
 	supplier
+	support
 ;
 
 local sourceDir ;
@@ -21,8 +22,16 @@ Application MediaPlayer :
 	MediaTrackVideoSupplier.cpp
 	VideoSupplier.cpp
 
-	# .
+	# support
 	AbstractLOAdapter.cpp
+	Command.cpp
+	CommandStack.cpp
+	Listener.cpp
+	ListenerAdapter.cpp
+	Notifier.cpp
+	RWLocker.cpp
+
+	# .
 	Controller.cpp
 	ControllerObserver.cpp
 	ControllerView.cpp

src/apps/mediaplayer/MainWin.cpp

@@ -166,6 +166,15 @@ MainWin::MainWin()
 
 	_SetupWindow();
 
+	// setup the playlist window now, we need to have it 
+	// running for the undo/redo playlist editing
+	fPlaylistWindow = new PlaylistWindow(BRect(150, 150, 400, 500),
+		fPlaylist, fController);
+	fPlaylistWindow->Hide();
+	fPlaylistWindow->Show();
+		// this makes sure the window thread is running without
+		// showing the window just yet
+
 	Show();
 }
 
@@ -683,13 +692,6 @@ MainWin::ShowFileInfo()
 void
 MainWin::ShowPlaylistWindow()
 {
-	if (!fPlaylistWindow) {
-		fPlaylistWindow = new PlaylistWindow(BRect(150, 150, 400, 500),
-			fPlaylist, fController);
-		fPlaylistWindow->Show();
-		return;
-	}
-
 	if (fPlaylistWindow->Lock()) {
 		if (fPlaylistWindow->IsHidden())
 			fPlaylistWindow->Show();
@@ -728,15 +730,18 @@ MainWin::VideoFormatChange(int width, int height, float width_scale, float heigh
 
 
 void
-MainWin::_RefsReceived(BMessage *msg)
+MainWin::_RefsReceived(BMessage* msg)
 {
 	// the playlist ist replaced by dropped files
 	// or the dropped files are appended to the end
 	// of the existing playlist if <shift> is pressed
 	int32 appendIndex = modifiers() & B_SHIFT_KEY ?
 		fPlaylist->CountItems() : -1;
+	msg->AddInt32("append_index", appendIndex);
 
-	fPlaylist->AppendRefs(msg, appendIndex);
+	// forward the message to the playlist window,
+	// so that undo/redo is used for modifying the playlist
+	fPlaylistWindow->PostMessage(msg);
 }
 
 

src/apps/mediaplayer/PlaylistListView.cpp

@@ -252,12 +252,12 @@ PlaylistListView::MessageReceived(BMessage* message)
 
 		case B_SIMPLE_DATA:
 			if (message->HasRef("refs"))
-				_RefsReceived(message, fDropIndex);
+				RefsReceived(message, fDropIndex);
 			else if (message->HasPointer("list"))
 				SimpleListView::MessageReceived(message);
 			break;
 		case B_REFS_RECEIVED:
-			_RefsReceived(message, fDropIndex);
+			RefsReceived(message, fDropIndex);
 			break;
 
 		default:
@@ -421,6 +421,18 @@ PlaylistListView::DrawListItem(BView* owner, int32 index, BRect frame) const
 }
 
 
+void
+PlaylistListView::RefsReceived(BMessage* message, int32 appendIndex)
+{
+	if (!fPlaylist->Lock())
+		return;
+
+	fPlaylist->AppendRefs(message, appendIndex);
+
+	fPlaylist->Unlock();
+}
+
+
 // #pragma mark -
 
 
@@ -489,14 +501,3 @@ PlaylistListView::_SetPlaybackState(uint32 state)
 }
 
 
-void
-PlaylistListView::_RefsReceived(BMessage* message, int32 dropIndex)
-{
-	if (!fPlaylist->Lock())
-		return;
-
-	fPlaylist->AppendRefs(message, dropIndex);
-
-	fPlaylist->Unlock();
-}
-

src/apps/mediaplayer/PlaylistListView.h

@@ -38,6 +38,10 @@ class PlaylistListView : public SimpleListView {
 	virtual	void				DrawListItem(BView* owner, int32 index,
 									BRect frame) const;
 
+	// PlaylistListView
+			void				RefsReceived(BMessage* message,
+									int32 appendIndex);
+
  private:
 			void				_FullSync();
 			void				_AddItem(const entry_ref& ref, int32 index);
@@ -46,9 +50,6 @@ class PlaylistListView : public SimpleListView {
 			void				_SetCurrentPlaylistIndex(int32 index);
 			void				_SetPlaybackState(uint32 state);
 
-			void				_RefsReceived(BMessage* message,
-									int32 dropIndex);
-
 			Playlist*			fPlaylist;
 			PlaylistObserver*	fPlaylistObserver;
 

src/apps/mediaplayer/PlaylistWindow.cpp

@@ -7,25 +7,50 @@
  */
 #include "PlaylistWindow.h"
 
+#include <Menu.h>
+#include <MenuBar.h>
+#include <MenuItem.h>
 #include <ScrollBar.h>
 #include <ScrollView.h>
+#include <String.h>
 
+#include "CommandStack.h"
 #include "PlaylistListView.h"
+#include "RWLocker.h"
 
 
 PlaylistWindow::PlaylistWindow(BRect frame, Playlist* playlist,
 		Controller* controller)
-	: BWindow(frame, "Playlist", B_TITLED_WINDOW, B_ASYNCHRONOUS_CONTROLS)
+	: BWindow(frame, "Playlist", B_DOCUMENT_WINDOW_LOOK, B_NORMAL_WINDOW_FEEL,
+		B_ASYNCHRONOUS_CONTROLS)
+
+	, fLocker(new RWLocker("command stack lock"))
+	, fCommandStack(new CommandStack(fLocker))
+	, fCommandStackListener(this)
 {
 	frame = Bounds();
+
+	_CreateMenu(frame);
+
 	frame.right -= B_V_SCROLL_BAR_WIDTH;
-	PlaylistListView* listView = new PlaylistListView(frame, playlist,
-		controller);
+	fListView = new PlaylistListView(frame, playlist, controller);
 
-	fTopView = new BScrollView("playlist scrollview",
-		listView, B_FOLLOW_ALL, 0, false, true, B_NO_BORDER);
+	BScrollView* scrollView = new BScrollView("playlist scrollview",
+		fListView, B_FOLLOW_ALL, 0, false, true, B_NO_BORDER);
 
+	fTopView = scrollView;
 	AddChild(fTopView);
+
+	// small visual tweak
+	if (BScrollBar* scrollBar = scrollView->ScrollBar(B_VERTICAL)) {
+		// make it so the frame of the menubar is also the frame of
+		// the scroll bar (appears to be)
+		scrollBar->MoveBy(0, -1);
+		scrollBar->ResizeBy(0, 1);
+	}
+
+	fCommandStack->AddListener(&fCommandStackListener);
+	_ObjectChanged(fCommandStack);
 }
 
 
@@ -34,6 +59,10 @@ PlaylistWindow::~PlaylistWindow()
 	// give listeners a chance to detach themselves
 	fTopView->RemoveSelf();
 	delete fTopView;
+
+	fCommandStack->RemoveListener(&fCommandStackListener);
+	delete fCommandStack;
+	delete fLocker;
 }
 
 
@@ -53,9 +82,91 @@ PlaylistWindow::MessageReceived(BMessage* message)
 			if (LastMouseMovedView())
 				PostMessage(message, LastMouseMovedView());
 			break;
+
+		case B_UNDO:
+			fCommandStack->Undo();
+			break;
+		case B_REDO:
+			fCommandStack->Redo();
+			break;
+
+		case MSG_OBJECT_CHANGED: {
+			Notifier* notifier;
+			if (message->FindPointer("object", (void**)&notifier) == B_OK)
+				_ObjectChanged(notifier);
+			break;
+		}
+
+		case B_REFS_RECEIVED:
+		case B_SIMPLE_DATA: {
+			// only accept this message when it comes from the
+			// player window, _not_ when it is dropped in this window
+			// outside of the playlist!
+			int32 appendIndex;
+			if (message->FindInt32("append_index", &appendIndex) == B_OK) {
+				fListView->RefsReceived(message, appendIndex);
+			}
+			break;
+		}
+
 		default:
 			BWindow::MessageReceived(message);
 			break;
 	}
 }
 
+
+// #pragma mark -
+
+
+void
+PlaylistWindow::_CreateMenu(BRect& frame)
+{
+	frame.bottom = 15;
+	BMenuBar* menuBar = new BMenuBar(frame, "main menu");
+	BMenu* fileMenu = new BMenu("Playlist");
+	menuBar->AddItem(fileMenu);
+	// TODO add some items: "Open", "Save", "Make Empty"...
+
+	BMenu* editMenu = new BMenu("Edit");
+	BMessage* message = new BMessage(B_UNDO);
+	fUndoMI = new BMenuItem("Undo", message);
+	editMenu->AddItem(fUndoMI);
+	message = new BMessage(B_REDO);
+	fRedoMI = new BMenuItem("Undo", message);
+	editMenu->AddItem(fRedoMI);
+	menuBar->AddItem(editMenu);
+
+	AddChild(menuBar);
+	fileMenu->SetTargetForItems(this);
+	editMenu->SetTargetForItems(this);
+
+	menuBar->ResizeToPreferred();
+	frame = Bounds();
+	frame.top = menuBar->Frame().bottom + 1;
+}
+
+
+// _ObjectChanged
+void
+PlaylistWindow::_ObjectChanged(const Notifier* object)
+{
+	if (object == fCommandStack) {
+		// relable Undo item and update enabled status
+		BString label("Undo");
+		fUndoMI->SetEnabled(fCommandStack->GetUndoName(label));
+		if (fUndoMI->IsEnabled())
+			fUndoMI->SetLabel(label.String());
+		else
+			fUndoMI->SetLabel("<nothing to undo>");
+
+		// relable Redo item and update enabled status
+		label.SetTo("Redo");
+		fRedoMI->SetEnabled(fCommandStack->GetRedoName(label));
+		if (fRedoMI->IsEnabled())
+			fRedoMI->SetLabel(label.String());
+		else
+			fRedoMI->SetLabel("<nothing to redo>");
+	}
+}
+

src/apps/mediaplayer/PlaylistWindow.h

@@ -11,8 +11,16 @@
 
 #include <Window.h>
 
+#include "ListenerAdapter.h"
+
+class BMenuBar;
+class BMenuItem;
+class CommandStack;
 class Controller;
+class Notifier;
 class Playlist;
+class PlaylistListView;
+class RWLocker;
 
 class PlaylistWindow : public BWindow {
  public:
@@ -25,7 +33,19 @@ class PlaylistWindow : public BWindow {
 	virtual	void				MessageReceived(BMessage* message);
 
  private:
+			void				_CreateMenu(BRect& frame);
+			void				_ObjectChanged(const Notifier* object);
+
+			Playlist*			fPlaylist;
+			PlaylistListView*	fListView;
+
 			BView*				fTopView;
+			BMenuItem*			fUndoMI;
+			BMenuItem*			fRedoMI;
+
+			RWLocker*			fLocker;
+			CommandStack*		fCommandStack;
+			ListenerAdapter		fCommandStackListener;
 };
 
 #endif // PLAYLIST_WINDOW_H

src/apps/mediaplayer/support/Command.cpp

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2006, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+
+#include "Command.h"
+
+#include <stdio.h>
+
+#include <OS.h>
+
+// constructor
+Command::Command()
+	: fTimeStamp(system_time())
+{
+}
+
+// destructor
+Command::~Command()
+{
+}
+
+// InitCheck
+status_t
+Command::InitCheck()
+{
+	return B_NO_INIT;
+}
+
+// Perform
+status_t
+Command::Perform()
+{
+	return B_ERROR;
+}
+
+// Undo
+status_t
+Command::Undo()
+{
+	return B_ERROR;
+}
+
+// Redo
+status_t
+Command::Redo()
+{
+	return Perform();
+}
+
+// GetName
+void
+Command::GetName(BString& name)
+{
+	name << "Name of action goes here.";
+}
+
+// UndoesPrevious
+bool
+Command::UndoesPrevious(const Command* previous)
+{
+	return false;
+}
+
+// CombineWithNext
+bool
+Command::CombineWithNext(const Command* next)
+{
+	return false;
+}
+
+// CombineWithPrevious
+bool
+Command::CombineWithPrevious(const Command* previous)
+{
+	return false;
+}
+
+
+// _GetString
+const char*
+Command::_GetString(uint32 key, const char* defaultString) const
+{
+//	if (LanguageManager* manager = LanguageManager::Default())
+//		return manager->GetString(key, defaultString);
+//	else
+		return defaultString;
+}

src/apps/mediaplayer/support/Command.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2006, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+
+#ifndef COMMAND_H
+#define COMMAND_H
+
+#include <SupportDefs.h>
+#include <String.h>
+
+class BString;
+
+class Command {
+ public:
+								Command();
+	virtual						~Command();
+	
+	virtual	status_t			InitCheck();
+
+	virtual	status_t			Perform();
+	virtual status_t			Undo();
+	virtual status_t			Redo();
+
+	virtual void				GetName(BString& name);
+
+	virtual	bool				UndoesPrevious(const Command* previous);
+	virtual	bool				CombineWithNext(const Command* next);
+	virtual	bool				CombineWithPrevious(const Command* previous);
+
+ protected:
+			const char*			_GetString(uint32 key,
+										   const char* defaultString) const;
+
+			bigtime_t			fTimeStamp;
+};
+
+#endif // COMMAND_H

src/apps/mediaplayer/support/CommandStack.cpp

@@ -0,0 +1,252 @@
+/*
+ * Copyright 2006-2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+
+#include "CommandStack.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <Locker.h>
+#include <String.h>
+
+#include "Command.h"
+#include "RWLocker.h"
+
+// constructor
+CommandStack::CommandStack(RWLocker* locker)
+	: Notifier()
+	, fLocker(locker)
+	, fSavedCommand(NULL)
+{
+}
+
+// destructor
+CommandStack::~CommandStack()
+{
+	Clear();
+}
+
+// Perform
+status_t
+CommandStack::Perform(Command* command)
+{
+	if (!fLocker->WriteLock())
+		return B_ERROR;
+
+	status_t ret = command ? B_OK : B_BAD_VALUE;
+	if (ret == B_OK)
+		ret = command->InitCheck();
+
+	if (ret == B_OK)
+		ret = command->Perform();
+
+	if (ret == B_OK)
+		ret = _AddCommand(command);
+
+	if (ret != B_OK) {
+		// no one else feels responsible...
+		delete command;
+	}
+	fLocker->WriteUnlock();
+
+	Notify();
+
+	return ret;
+}
+
+// Undo
+status_t
+CommandStack::Undo()
+{
+	if (!fLocker->WriteLock())
+		return B_ERROR;
+
+	status_t status = B_ERROR;
+	if (!fUndoHistory.empty()) {
+		Command* command = fUndoHistory.top();
+		fUndoHistory.pop();
+		status = command->Undo();
+		if (status == B_OK)
+			fRedoHistory.push(command);
+		else
+			fUndoHistory.push(command);
+	}
+	fLocker->WriteUnlock();
+
+	Notify();
+
+	return status;
+}
+
+// Redo
+status_t
+CommandStack::Redo()
+{
+	if (!fLocker->WriteLock())
+		return B_ERROR;
+
+	status_t status = B_ERROR;
+	if (!fRedoHistory.empty()) {
+		Command* command = fRedoHistory.top();
+		fRedoHistory.pop();
+		status = command->Redo();
+		if (status == B_OK)
+			fUndoHistory.push(command);
+		else
+			fRedoHistory.push(command);
+	}
+	fLocker->WriteUnlock();
+
+	Notify();
+
+	return status;
+}
+
+// UndoName
+bool
+CommandStack::GetUndoName(BString& name)
+{
+	bool success = false;
+	if (fLocker->ReadLock()) {
+		if (!fUndoHistory.empty()) {
+			name << " ";
+			fUndoHistory.top()->GetName(name);
+			success = true;
+		}
+		fLocker->ReadUnlock();
+	}
+	return success;
+}
+
+// RedoName
+bool
+CommandStack::GetRedoName(BString& name)
+{
+	bool success = false;
+	if (fLocker->ReadLock()) {
+		if (!fRedoHistory.empty()) {
+			name << " ";
+			fRedoHistory.top()->GetName(name);
+			success = true;
+		}
+		fLocker->ReadUnlock();
+	}
+	return success;
+}
+
+// Clear
+void
+CommandStack::Clear()
+{
+	if (fLocker->WriteLock()) {
+		while (!fUndoHistory.empty()) {
+			delete fUndoHistory.top();
+			fUndoHistory.pop();
+		}
+		while (!fRedoHistory.empty()) {
+			delete fRedoHistory.top();
+			fRedoHistory.pop();
+		}
+		fLocker->WriteUnlock();
+	}
+
+	Notify();
+}
+
+// Save
+void
+CommandStack::Save()
+{
+	if (fLocker->WriteLock()) {
+		if (!fUndoHistory.empty())
+			fSavedCommand = fUndoHistory.top();
+		fLocker->WriteUnlock();
+	}
+
+	Notify();
+}
+
+// IsSaved
+bool
+CommandStack::IsSaved()
+{
+	bool saved = false;
+	if (fLocker->ReadLock()) {
+		saved = fUndoHistory.empty();
+		if (fSavedCommand && !saved) {
+			if (fSavedCommand == fUndoHistory.top())
+				saved = true;
+		}
+		fLocker->ReadUnlock();
+	}
+	return saved;
+}
+
+// #pragma mark -
+
+// _AddCommand
+status_t
+CommandStack::_AddCommand(Command* command)
+{
+	status_t status = B_OK;
+
+	bool add = true;
+	if (!fUndoHistory.empty()) {
+		// try to collapse commands to a single command
+		// or remove this and the previous command if
+		// they reverse each other
+		if (Command* top = fUndoHistory.top()) {
+			if (command->UndoesPrevious(top)) {
+				add = false;
+				fUndoHistory.pop();
+				delete top;
+				delete command;
+			} else if (top->CombineWithNext(command)) {
+				add = false;
+				delete command;
+				// after collapsing, the command might
+				// have changed it's mind about InitCheck()
+				// (the commands reversed each other)
+				if (top->InitCheck() < B_OK) {
+					fUndoHistory.pop();
+					delete top;
+				}
+			} else if (command->CombineWithPrevious(top)) {
+				fUndoHistory.pop();
+				delete top;
+				// after collapsing, the command might
+				// have changed it's mind about InitCheck()
+				// (the commands reversed each other)
+				if (command->InitCheck() < B_OK) {
+					delete command;
+					add = false;
+				}
+			}
+		}
+	}
+	if (add) {
+		try {
+			fUndoHistory.push(command);
+		} catch (...) {
+			status = B_ERROR;
+		}
+	}
+
+	if (status == B_OK) {
+		// the redo stack needs to be empty
+		// as soon as a command was added (also in case of collapsing)
+		while (!fRedoHistory.empty()) {
+			delete fRedoHistory.top();
+			fRedoHistory.pop();
+		}
+	}
+
+	return status;
+}
+
+

src/apps/mediaplayer/support/CommandStack.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2006-2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+#ifndef COMMAND_STACK_H
+#define COMMAND_STACK_H
+
+#include <stack.h>
+
+#include "Notifier.h"
+
+class BString;
+class RWLocker;
+class Command;
+
+class CommandStack : public Notifier {
+ public:
+								CommandStack(RWLocker* locker);
+	virtual						~CommandStack();
+
+			status_t			Perform(Command* command);
+
+			status_t			Undo();
+			status_t			Redo();
+
+			bool				GetUndoName(BString& name);
+			bool				GetRedoName(BString& name);
+
+			void				Clear();
+			void				Save();
+			bool				IsSaved();
+
+ private:
+			status_t			_AddCommand(Command* command);
+
+			RWLocker*			fLocker;
+
+	typedef stack<Command*> command_stack;
+
+			command_stack		fUndoHistory;
+			command_stack		fRedoHistory;
+			Command*			fSavedCommand;
+};
+
+#endif // COMMAND_STACK_H

src/apps/mediaplayer/support/Listener.cpp

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2006, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+
+#include "Listener.h"
+
+Listener::Listener()
+{
+}
+
+Listener::~Listener()
+{
+}
+

src/apps/mediaplayer/support/Listener.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2006-2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+#ifndef LISTENER_H
+#define LISTENER_H
+
+#include <SupportDefs.h>
+
+class Notifier;
+
+class Listener {
+ public:
+								Listener();
+	virtual						~Listener();
+
+	virtual	void				ObjectChanged(const Notifier* object) = 0;
+};
+
+#endif // LISTENER_H

src/apps/mediaplayer/support/ListenerAdapter.cpp

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2006, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+#include "ListenerAdapter.h"
+
+#include <Message.h>
+
+// constructor
+ListenerAdapter::ListenerAdapter(BHandler* handler)
+	: Listener()
+	, AbstractLOAdapter(handler)
+{
+}
+
+// destructor
+ListenerAdapter::~ListenerAdapter()
+{
+}
+
+// ObjectChanged
+void
+ListenerAdapter::ObjectChanged(const Notifier* object)
+{
+	BMessage message(MSG_OBJECT_CHANGED);
+	message.AddPointer("object", object);
+
+	DeliverMessage(message);
+}

src/apps/mediaplayer/support/ListenerAdapter.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+#ifndef LISTENER_ADAPTER_H
+#define LISTENER_ADAPTER_H
+
+#include "AbstractLOAdapter.h"
+#include "Listener.h"
+
+enum {
+	MSG_OBJECT_CHANGED	= 'obch'
+};
+
+class ListenerAdapter : public Listener, public AbstractLOAdapter {
+ public:
+								ListenerAdapter(BHandler* handler);
+	virtual						~ListenerAdapter();
+
+	virtual	void				ObjectChanged(const Notifier* object);
+};
+
+#endif // LISTENER_ADAPTER_H

src/apps/mediaplayer/support/NOTE

@@ -0,0 +1,3 @@
+This folder contains some generic classes. The same code is used in Icon-O-Matic btw. I should move my lazy butt and place this code somewhere common. Ideas?
+
+-Stephan

src/apps/mediaplayer/support/Notifier.cpp

@@ -0,0 +1,105 @@
+/*
+ * Copyright 2006-2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+
+#include "Notifier.h"
+
+#include <stdio.h>
+#include <typeinfo>
+
+#include <OS.h>
+
+#include "Listener.h"
+
+// constructor
+Notifier::Notifier()
+	: fListeners(2),
+	  fSuspended(0),
+	  fPendingNotifications(false)
+{
+}
+
+// destructor
+Notifier::~Notifier()
+{
+	if (fListeners.CountItems() > 0) {
+		char message[256];
+		Listener* o = (Listener*)fListeners.ItemAt(0);
+		sprintf(message, "Notifier::~Notifier() - %ld "
+						 "listeners still watching, first: %s\n",
+						 fListeners.CountItems(), typeid(*o).name());
+		debugger(message);
+	}
+}
+
+// AddListener
+bool
+Notifier::AddListener(Listener* listener)
+{
+	if (listener && !fListeners.HasItem((void*)listener)) {
+		return fListeners.AddItem((void*)listener);
+	}
+	return false;
+}
+
+// RemoveListener
+bool
+Notifier::RemoveListener(Listener* listener)
+{
+	return fListeners.RemoveItem((void*)listener);
+}
+
+// CountListeners
+int32
+Notifier::CountListeners() const
+{
+	return fListeners.CountItems();
+}
+
+// ListenerAtFast
+Listener*
+Notifier::ListenerAtFast(int32 index) const
+{
+	return (Listener*)fListeners.ItemAtFast(index);
+}
+
+// #pragma mark -
+
+// Notify
+void
+Notifier::Notify() const
+{
+	if (!fSuspended) {
+		BList observers(fListeners);
+		int32 count = observers.CountItems();
+		for (int32 i = 0; i < count; i++)
+			((Listener*)observers.ItemAtFast(i))->ObjectChanged(this);
+		fPendingNotifications = false;
+	} else {
+		fPendingNotifications = true;
+	}
+}
+
+// SuspendNotifications
+void
+Notifier::SuspendNotifications(bool suspend)
+{
+	if (suspend)
+		fSuspended++;
+	else
+		fSuspended--;
+
+	if (fSuspended < 0) {
+		fprintf(stderr, "Notifier::SuspendNotifications(false) - "
+						"error: suspend level below zero!\n");
+		fSuspended = 0;
+	}
+
+	if (!fSuspended && fPendingNotifications)
+		Notify();
+}
+

src/apps/mediaplayer/support/Notifier.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2006-2007, Haiku.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Stephan Aßmus <superstippi@gmx.de>
+ */
+#ifndef NOTIFIER_H
+#define NOTIFIER_H
+
+#include <List.h>
+
+class Listener;
+
+class Notifier {
+ public:
+								Notifier();
+	virtual						~Notifier();
+
+			bool				AddListener(Listener* listener);
+			bool				RemoveListener(Listener* listener);
+
+			int32				CountListeners() const;
+			Listener*			ListenerAtFast(int32 index) const;
+	
+	 		void				Notify() const;
+
+			void				SuspendNotifications(bool suspend);
+
+			bool				HasPendingNotifications() const
+									{ return fPendingNotifications; }
+
+ private:
+			BList				fListeners;
+
+			int32				fSuspended;
+	mutable	bool				fPendingNotifications;
+};
+
+class AutoNotificationSuspender {
+ public:
+								AutoNotificationSuspender(Notifier* object)
+									: fObject(object)
+								{
+									fObject->SuspendNotifications(true);
+								}
+
+	virtual						~AutoNotificationSuspender()
+								{
+									fObject->SuspendNotifications(false);
+								}
+ private:
+			Notifier*			fObject;
+};
+
+#endif // NOTIFIER_H