ShellNotify Class

Properties   Methods   Events   Config Settings   Errors  

The ShellNotify class enables monitoring file system change notifications.

Syntax

ShellNotify

Remarks

The ShellNotify class provides a simple way to monitor changes such as creation, renaming, deletion, or modification of files or folders. The class uses the Windows API to register as an observer of shell notifications.

Activate

First, set the Path property to the desired location to listen for changes. The target may be a local or remote filesystem, and a path may be specified using the drive letter format or a UNC path. For instance, you can set C:\Path\To\Folder if the target is a mapped drive, or \\servername\sharename if the target is a network share.

After that, you may set the Recursive property depending on whether you would like to include changes for subfolders. You may also set the value of Notifications to control the types of changes to monitor.

ShellNotify component = new ShellNotify(); component.Path = "C:\Temp"; component.Recursive = True;

The next step is to call Activate to begin listening for changes. As users interact with files and folders at the specified Path, the corresponding events will be triggered. Activate must be called again if the Explorer process is terminated.

component.Activate();

Deactivate

To unregister as an observer of changes, call the Deactivate method. This action will cease monitoring change notifications and only needs to be called once.

component.Deactivate();

PIDLs

A PIDL (or an IDL) is a fundamental Windows Shell concept. At a high level, it is pretty simple, as it is just a value that represents a Windows Shell item in the Windows Shell Namespace. It is a bit like a full filesystem path for a physical file or folder, except that it is a binary object and not a string. The name "PIDL" and "IDL" can be used interchangeably. The leading P stands for pointer, the IDL stands for item identifier list, and PIDL generally refers to an IDL itself rather than the pointer to it.

The below information is provided as a general knowledge. Your application will deal with PIDLs only when they denote some Windows Shell items that are not necessarily a part of the Windows Shell namespace extension that you create. Such PIDLs can be used with the Windows Shell API if you decide to call it directly. When CBFS Shell exposes these PIDL values they will appear hex-encoded. If an application needs to call a shell function, it has to decode the PIDL before calling that function.

Just like a full filesystem path is a list of strings separated by the directory separator (on Windows, it is the \ (backslash) character), a PIDL is a list (L is for list) of Ids (identifiers). Unlike a filesystem path, though, a PIDL is binary, and Ids are separated by a special PIDL separator (two consecutive zero bytes).

Microsoft provides more details about PIDLs here Identifying Namespace Objects.

Troubleshooting

Following are some helpful resources for troubleshooting issues.

• If events are not triggered for any changes, note that the class relies on Explorer running and not terminating or restarting. If the Explorer process ends then you will need to call Activate again.
• If certain events are not triggered, it may be that the system components behave differently depending on the target you are monitoring. For instance, to monitor changes to a network share one needs to handle ItemChanged.
• If you are seeing strange behavior not contained in this list, please reach out to us with a description of the problem and we are happy to help. Our support team is available over email at support@callback.com

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

Notifications Property (ShellNotify Class)

The property specifies which changes to monitor.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetNotifications();
int SetNotifications(int iNotifications);

Unicode (Windows)
INT GetNotifications();
INT SetNotifications(INT iNotifications);

int cbfsshell_shellnotify_getnotifications(void* lpObj);
int cbfsshell_shellnotify_setnotifications(void* lpObj, int iNotifications);

int GetNotifications();
int SetNotifications(int iNotifications);

Default Value

0x0002001F

Remarks

The property specifies which changes the class should monitor. The value may be a combination of the following flags:

The default value of 0x0002001F (CHANGE_NOTIFY_DEFAULT) is a combination of the following flags:

• CHANGE_NOTIFY_CREATE
• CHANGE_NOTIFY_CREATE_FOLDER
• CHANGE_NOTIFY_DELETE
• CHANGE_NOTIFY_DELETE_FOLDER
• CHANGE_NOTIFY_RENAME
• CHANGE_NOTIFY_RENAME_FOLDER

Data Type

Integer

Path Property (ShellNotify Class)

The property specifies what path or namespace item to monitor.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetPath();
int SetPath(const char* lpszPath);

Unicode (Windows)
LPWSTR GetPath();
INT SetPath(LPCWSTR lpszPath);

char* cbfsshell_shellnotify_getpath(void* lpObj);
int cbfsshell_shellnotify_setpath(void* lpObj, const char* lpszPath);

QString GetPath();
int SetPath(QString qsPath);

Default Value

""

Remarks

This property specifies the target to monitor. If omitted, all of the Windows Shell namespace is monitored. A target may be any namespace item such as a folder or non-folder item.

An application may set this property to a filesystem path in drive-letter format, a path in UNC format, or a hex-encoded PIDL if a Windows Shell folder or item with no filesystem path is to be monitored. For instance:

• C:\Path\To\Folder
• \\<server>\<share>

Data Type

String

Recursive Property (ShellNotify Class)

This property specifies whether changes in subfolders should be monitored.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetRecursive();
int SetRecursive(int bRecursive);

Unicode (Windows)
BOOL GetRecursive();
INT SetRecursive(BOOL bRecursive);

int cbfsshell_shellnotify_getrecursive(void* lpObj);
int cbfsshell_shellnotify_setrecursive(void* lpObj, int bRecursive);

bool GetRecursive();
int SetRecursive(bool bRecursive);

Default Value

TRUE

Remarks

This property specifies whether changes in subfolders of the folder specified by Path property should also be monitored. This setting will be ignored if the Path property references a non-folder item.

Data Type

Boolean

Activate Method (ShellNotify Class)

This method initiates monitoring for changes.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Activate();

Unicode (Windows)
INT Activate();

int cbfsshell_shellnotify_activate(void* lpObj);

int Activate();

Remarks

Use this method to begin monitoring for changes in the target location specified by the Path property. The types of changes that will be included in monitoring are set in the Notifications property.

Activate must be called again if the Explorer process is terminated.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Config Method (ShellNotify Class)

Sets or retrieves a configuration setting.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* Config(const char* lpszConfigurationString);

Unicode (Windows)
LPWSTR Config(LPCWSTR lpszConfigurationString);

char* cbfsshell_shellnotify_config(void* lpObj, const char* lpszConfigurationString);

QString Config(const QString& qsConfigurationString);

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Error Handling (C++)

This method returns a String value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

Deactivate Method (ShellNotify Class)

This method stops monitoring changes.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Deactivate();

Unicode (Windows)
INT Deactivate();

int cbfsshell_shellnotify_deactivate(void* lpObj);

int Deactivate();

Remarks

Use this method to stop monitoring for changes and unregister as an observer of change notifications.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Error Event (ShellNotify Class)

This event is fired if an unhandled error occurs during an event.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireError(ShellNotifyErrorEventParams *e);

typedef struct {
  int ErrorCode;
  const char *Description;
  int reserved;
} ShellNotifyErrorEventParams;


Unicode (Windows)
virtual INT FireError(ShellNotifyErrorEventParams *e);

typedef struct {
  INT ErrorCode;
  LPCWSTR Description;
  INT reserved;
} ShellNotifyErrorEventParams;

#define EID_SHELLNOTIFY_ERROR 1

virtual INT CBFSSHELL_CALL FireError(INT &iErrorCode, LPSTR &lpszDescription);

class ShellNotifyErrorEventParams {
public:
  int ErrorCode();

  const QString &Description();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void Error(ShellNotifyErrorEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireError(ShellNotifyErrorEventParams *e) {...}

Remarks

This event fires if an unhandled error occurs. Developers can use this information to track down unhandled errors that occur in the class.

ErrorCode contains an error code and Description contains a textual description of the error.

FileCreated Event (ShellNotify Class)

This event fires when a file is created.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFileCreated(ShellNotifyFileCreatedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  int reserved;
} ShellNotifyFileCreatedEventParams;


Unicode (Windows)
virtual INT FireFileCreated(ShellNotifyFileCreatedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  INT reserved;
} ShellNotifyFileCreatedEventParams;

#define EID_SHELLNOTIFY_FILECREATED 2

virtual INT CBFSSHELL_CALL FireFileCreated(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath);

class ShellNotifyFileCreatedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FileCreated(ShellNotifyFileCreatedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFileCreated(ShellNotifyFileCreatedEventParams *e) {...}

Remarks

This event fires upon creation, when the Windows Shell registers file creation within the namespace.

PIDL contains a byte array that represents an item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

FileDeleted Event (ShellNotify Class)

This event fires when a file is deleted.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFileDeleted(ShellNotifyFileDeletedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  int reserved;
} ShellNotifyFileDeletedEventParams;


Unicode (Windows)
virtual INT FireFileDeleted(ShellNotifyFileDeletedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  INT reserved;
} ShellNotifyFileDeletedEventParams;

#define EID_SHELLNOTIFY_FILEDELETED 3

virtual INT CBFSSHELL_CALL FireFileDeleted(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath);

class ShellNotifyFileDeletedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FileDeleted(ShellNotifyFileDeletedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFileDeleted(ShellNotifyFileDeletedEventParams *e) {...}

Remarks

This event fires upon deletion, when the Windows Shell has registered file deletion.

PIDL contains a byte array that represents an item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

FileRenamed Event (ShellNotify Class)

This event fires when a file is renamed.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFileRenamed(ShellNotifyFileRenamedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  const char *NewPIDL;
  int lenNewPIDL;
  const char *NewPath;
  int reserved;
} ShellNotifyFileRenamedEventParams;


Unicode (Windows)
virtual INT FireFileRenamed(ShellNotifyFileRenamedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  LPCSTR NewPIDL;
  INT lenNewPIDL;
  LPCWSTR NewPath;
  INT reserved;
} ShellNotifyFileRenamedEventParams;

#define EID_SHELLNOTIFY_FILERENAMED 4

virtual INT CBFSSHELL_CALL FireFileRenamed(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath, LPSTR &lpNewPIDL, INT &lenNewPIDL, LPWSTR &lpszNewPath);

class ShellNotifyFileRenamedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  const QByteArray &NewPIDL();

  const QString &NewPath();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FileRenamed(ShellNotifyFileRenamedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFileRenamed(ShellNotifyFileRenamedEventParams *e) {...}

Remarks

This event fires upon renaming, when the Windows Shell has registered file renaming in one or more Windows Shell items.

PIDL contains a byte array that represents an previous item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full previous path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

NewPIDL contains the new PIDL.

NewPath contains the new path. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

FolderCreated Event (ShellNotify Class)

This event fires when a folder is created.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFolderCreated(ShellNotifyFolderCreatedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  int reserved;
} ShellNotifyFolderCreatedEventParams;


Unicode (Windows)
virtual INT FireFolderCreated(ShellNotifyFolderCreatedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  INT reserved;
} ShellNotifyFolderCreatedEventParams;

#define EID_SHELLNOTIFY_FOLDERCREATED 5

virtual INT CBFSSHELL_CALL FireFolderCreated(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath);

class ShellNotifyFolderCreatedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FolderCreated(ShellNotifyFolderCreatedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFolderCreated(ShellNotifyFolderCreatedEventParams *e) {...}

Remarks

This event fires upon folder creation, when the Windows Shell has registered a folder is created.

PIDL contains a byte array that represents an item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

FolderDeleted Event (ShellNotify Class)

This event fires when a folder is deleted.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFolderDeleted(ShellNotifyFolderDeletedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  int reserved;
} ShellNotifyFolderDeletedEventParams;


Unicode (Windows)
virtual INT FireFolderDeleted(ShellNotifyFolderDeletedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  INT reserved;
} ShellNotifyFolderDeletedEventParams;

#define EID_SHELLNOTIFY_FOLDERDELETED 6

virtual INT CBFSSHELL_CALL FireFolderDeleted(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath);

class ShellNotifyFolderDeletedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FolderDeleted(ShellNotifyFolderDeletedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFolderDeleted(ShellNotifyFolderDeletedEventParams *e) {...}

Remarks

This event fires upon folder deletion, when the Windows Shell has registered a folder has been deleted.

PIDL contains a byte array that represents an item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

FolderRenamed Event (ShellNotify Class)

This event fires when a folder is renamed.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireFolderRenamed(ShellNotifyFolderRenamedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  const char *NewPIDL;
  int lenNewPIDL;
  const char *NewPath;
  int reserved;
} ShellNotifyFolderRenamedEventParams;


Unicode (Windows)
virtual INT FireFolderRenamed(ShellNotifyFolderRenamedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  LPCSTR NewPIDL;
  INT lenNewPIDL;
  LPCWSTR NewPath;
  INT reserved;
} ShellNotifyFolderRenamedEventParams;

#define EID_SHELLNOTIFY_FOLDERRENAMED 7

virtual INT CBFSSHELL_CALL FireFolderRenamed(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath, LPSTR &lpNewPIDL, INT &lenNewPIDL, LPWSTR &lpszNewPath);

class ShellNotifyFolderRenamedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  const QByteArray &NewPIDL();

  const QString &NewPath();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void FolderRenamed(ShellNotifyFolderRenamedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireFolderRenamed(ShellNotifyFolderRenamedEventParams *e) {...}

Remarks

This event fires upon folder renaming, when the Windows Shell has registered renaming in one or more Windows Shell items.

PIDL contains a byte array that represents an previous item in the Windows Shell namespace. Please see PIDL for more information.

Path contains the full previous path of the item. This parameter is only applicable when the item is part of a filesystem with a path.

NewPIDL contains a new PIDL.

NewPath contains a new path. This parameter is only applicable when the item is part of a filesystem with a path.

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

ItemChanged Event (ShellNotify Class)

This event fires when any item is changed.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireItemChanged(ShellNotifyItemChangedEventParams *e);

typedef struct {
  const char *PIDL;
  int lenPIDL;
  const char *Path;
  const char *NewPIDL;
  int lenNewPIDL;
  const char *NewPath;
  int Changes;
  int reserved;
} ShellNotifyItemChangedEventParams;


Unicode (Windows)
virtual INT FireItemChanged(ShellNotifyItemChangedEventParams *e);

typedef struct {
  LPCSTR PIDL;
  INT lenPIDL;
  LPCWSTR Path;
  LPCSTR NewPIDL;
  INT lenNewPIDL;
  LPCWSTR NewPath;
  INT Changes;
  INT reserved;
} ShellNotifyItemChangedEventParams;

#define EID_SHELLNOTIFY_ITEMCHANGED 8

virtual INT CBFSSHELL_CALL FireItemChanged(LPSTR &lpPIDL, INT &lenPIDL, LPWSTR &lpszPath, LPSTR &lpNewPIDL, INT &lenNewPIDL, LPWSTR &lpszNewPath, INT &iChanges);

class ShellNotifyItemChangedEventParams {
public:
  const QByteArray &PIDL();

  const QString &Path();

  const QByteArray &NewPIDL();

  const QString &NewPath();

  int Changes();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void ItemChanged(ShellNotifyItemChangedEventParams *e);

// Or, subclass ShellNotify and override this emitter function.
virtual int FireItemChanged(ShellNotifyItemChangedEventParams *e) {...}

Remarks

This event fires upon any change, when the Windows Shell has registered a creation, deletion, renaming, or updates in one or more Windows Shell items. The types of updates can include changes to size, attributes, security settings, last write, and last access time.

PIDL contains a byte array that represents an item in the Windows Shell namespace. If the set of changes includes renaming, this parameter contains the previous PIDL. Please see PIDL for more information.

Path contains the full path of the item. This parameter is only applicable when the item is part of a filesystem with a path. If the set of changes includes renaming, this parameter contains the previous Path.

NewPIDL contains a new PIDL. This parameter is only used when the set of changes includes renaming.

NewPath contains a new path. This parameter is only used when the set of changes includes renaming.

Changes specifies the type of change. The value can be one of the following:

Note: The events are triggered in the same thread that the Windows Shell used for a notification. Performing time-consuming operations within this event will prevent other events firing in a timely manner and may affect overall performance.

Config Settings (ShellNotify Class)

Base Config Settings

Trappable Errors (ShellNotify Class)

Error Handling (C++)

Call the GetLastErrorCode() method to obtain the last called method's result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. Known error codes are listed below. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

ShellNotify Errors