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Environment: VC++ .NET, Windows 2000/XP, Windows Platform SDK
1. Introduction
Note: THIS CODE WILL WORK ONLY UNDER WINDOWS 2000/XP AND ABOVE
The System Tray is a familiar place for every reasonably experienced Windows OS user. Many applications use this area to place small icons here, which give information about their status. They give the user addition flexibility to directly interact with the application. Almost all applications provide a context menu over the system tray icons for interaction with the application. With the advent of Windows 2000/XP popup balloons can also be shown over the system tray icons, to notify the user of any relevant event. This article explains the process of creating and showing icons in the system tray for any application. This also caters to multiple icons to be shown for the same application. You can also show popup balloons over the specified icons.
2. Using the Code
- Include the files SYSTRAYICON.H and SYSTRAYICON.CPP in your project.
- Create an object (a class) from
CSysTrayIcon
. In case you wish to process mouse messages over the icons, derive a class fromCSysTrayIcon
and override any or all of the mouse messages mentioned in Section 2.2. - Create the object of the class
CSysTrayIcon
or a class derived from CSysTrayIcon(preferably in the MainFrame class). - Create and manipulate icons in the system tray using the functions given in Section 2.1.
- Mouse messages are trapped, and overridable functions are provided for custom processing. See Section 2.2 for the list of overridable functions that are triggered by mouse messages.
2.1 Functions for Creating and Manipulation Icons In the System Tray
BOOL CreateIcon(HICON hIcon, UINT nIconID, PCSTR szTip)
Input parameters:
HICON hIcon
->
Handle to an icon to be shown in the system tray.
UINT nIconID
->
A user-defined icon ID. It can be any unsigned integer.
PCSTR szTip
->
A tooltip that is shown when the user moves the mouse over the icon.
Return Value:
TRUE
if an new tray icon with the ID nIconID
could be created, else FALSE
.
BOOL ShowIcon(UINT nIconID)
Input parameters:
UINT nIconID ->
The icon with this ID is to be shown.
Return value:
TRUE
if the icon with this ID exists and could be shown, else FALSE
.
BOOL HideIcon(UINT nIconID)
Hides the icon. It does not delete the icon from memory.
Input parameters:
UINT nIconID
->
The icon with this ID is to be hidden. It is not deleted from memory.
Return value:
TRUE
if the icon with this ID exists and could be hidden; else, FALSE
.
BOOL DeleteIcon(UINT nIconID)
Hides and deletes the icon from memory.
Input parameters:
UINT nIconID
->
The icon with this ID is to be hidden and deleted from memory.
Return value:
TRUE
if the icon with the ID exists and could be removed and deleted from the system tray and memory; else, FALSE
.
BOOL ChangeIconTip(UINT nIconID, CString strTip)
This changes the tooltip associated with the system tray icon.
Input parameters:
UINT nIconID
->
The icon with this ID whose tooltip has to be changed.
CString strTip
->
The new tooltip to be associated with this icon.
Return Values:
TRUE
if the icon with this ID exists and its tooltip cold be changed; else, FALSE
.
BOOL ShowBalloon(UINT nIconID, PTSTR szBalloonTitle, PTSTR szBalloonMsg, DWORD dwIcon = NIIF_NONE, UINT nTimeOut = 10)
Shows a popup balloon over the icon with the ID, nIconID.
Input parameters:
UINT nIconID
->
The icon ID over which the balloon will be shown.
PTSTR szBalloonTitle
->
A string for the heading of the balloon message
PTSTR szBalloonMsg
->
A string for the balloon message.
DWORD dwIcon
->
An additional symbol in the left corner of the balloon that will emphasize the meaning of the balloon. There are four possibilities, NIIF_NONE, NIIF_ERROR, NIIF_INFO, and NIIF_WARNING. The default is NIIF_NONE. These are standard constants defined in Windows Platform SDK in shellapi.h.
UINT nTimeOut
->
Time in seconds for the balloon to be visible. In Windows 2000/XP, the minimum is 10 seconds. Even if you specify a time less than 10 seconds, it will be visible for a minimum of 10 seconds. This will probably change with the future versions of Windows.
Return Value:
TRUE
if the balloon with given ID exists and the requested balloon could be shown; else, FALSE
.
2.2 Overridable Functions
There are ten overridable virtual functions, all of which deal with mouse messages.
virtual void OnLButtonDown(UINT nIconID, CPoint ptMouse)
Gets called when the left mouse button has been pressed
virtual void OnRButtonDown(UINT nIconID, CPoint ptMouse)
Gets called when the right mouse button has been pressed
virtual void OnMButtonDown(UINT nIconID, CPoint ptMouse)
Gets called when the middle mouse button has been pressed
virtual void OnLButtonUp(UINT nIconID, CPoint ptMouse)
Gets called when the left mouse button is released
virtual void OnRButtonUp(UINT nIconID, CPoint ptMouse)
Gets called when the right mouse button is released
virtual void OnMButtonUp(UINT nIconID, CPoint ptMouse)
Gets called when the middle mouse button is released
virtual void OnLButtonDblClk(UINT nIconID, CPoint ptMouse)
Gets called when the left mouse button is double-clicked
virtual void OnRButtonDblClk(UINT nIconID, CPoint ptMouse)
Gets called when the right mouse button is double-clicked
virtual void OnMButtonDblClk(UINT nIconID, CPoint ptMouse)
Gets called when the middle mouse button is double-clicked
virtual void OnMouseMove(UINT nIconID, CPoint ptMouse)
Gets called when the mouse moves over the icon
Input parameters for all overridables:
UINT nIconID
->
The icon ID over which the mouse message has been generated
CPoint ptMouse
-> The mouse position in screen co-ordinates
2.3 Helper Function for Handling a Context Menu
BOOL OnContextMenu(CMenu* pContextMenu, CPoint ptMouse, CWnd* pWndMessageHandler)
This function should be called by the programmer, as it will help him to do the requisite processing to show a context menu. This sets the window mentioned in the third parameter in the foreground, so that commands can be routed to it for processing.
This function should generally be called in response to a right button down message, typically in the overridden method OnRButtonDown
of the class derived from CSysTrayIcon
.
Input parameters:
CMenu* pContextMenu
->
Pointer to the menu to be shown, it is mostly on a right button press.
CPoint ptMouse
->
Mouse position in screen co-ordinates.
CWnd* pWndMessageHandler
->
A pointer to the window that will process the command handlers of the menu pContextMenu. This function on sets this window in the foreground so that it is capable of processing the command handlers. This function was written specifically for bringing the menu command handler receiver window to the foreground. In case you don’t bring the window that will receive the menu commands in the foreground, the commands won’t be routed properly. This window is generally the MainFrame window in a typical Windows application.
3. The Implementation of the Class CSysTrayIcon
The CSysTrayIcon
class is a wrapper around the Windows API, Shell_NotifyIcon
, and the Windows Platform SDK structure NOTIFYICONDATA
, which is declared in the header file shellapi.h. Details about the above mentioned API and structure are well documented in the MSDN documentation.
The class CSysTrayIcon
contains a linked list of NOTIFYICONDATA
structures (CSystrayIcon::NOTIFYICONDATAList
), which maintains information about each icon in the system tray related to that application. Every application can have more than one icon in the system tray. There is no restriction on an application to have only one system tray icon. It is only restricted by the maximum value of an unsigned integer!
Because this class CSysTrayIcon
can’t directly receive mouse messages, there has to be a way to route these messages to this class. This is done by creating a hidden window as a private member variable m_wndTrayMsgReceiver
(of type CSysTrayWnd
) in the class CSysTrayIcon
, which is registered to receive the WM_SYSTRAYMSG
. When a message WM_SYSTRAYMSG
is received by the window object CSysTrayIcon::m_wndTrayMsgReceiver
, it is mapped to CSysTrayWnd::OnSysTrayMsg(WPARAM wParam, LPARAM lParam)
. The lParam
gives the type of mouse message and the wParam
gives the icon ID on which the mouse message was generated. If you look at the implementation of CSysTrayIcon::CreateIcon()
, the NOTIFYICONDATA
structure members hWnd
and uCallBackMessage
are initialised as shown below. This is where the operating system comes to know which window is to be sent the WM_SYSTRAYMSG
.
pnidIconInfo->hWnd = m_wndTrayMsgReceiver. GetSafeHwnd(); pnidIconInfo->uCallbackMessage = WM_SYSTRAYMSG;
An object of the CSysTrayWnd
window is created in the constructor of CSysTrayIcon
itself. The CSystTrayWnd
also has a pointer to the CSysTrayIcon
class that helps in calling the virtual overridable functions as mentioned in Section 2.2.
There are few other functions that are used internally in the class to get the icons from the linked list, if given the icon ID as the parameter. These are summarized below.
GetNotifyIconDataFromID()
->
Retrieves the NOTIFYCOINDATA structure from the linked list CSysTrayIcon::NOTIFYICONDATAList for the given icon ID.
CheckIfIconIDExists()
->
This is called to check whether the icon with the given ID already exists, when creating a new system tray icon.
DeleteNotifyIconDataFromID()
->
This is called from the DeleteIcon()
function and the destructor of the CSystTrayIcon
class for deleting the icon and proper cleanup. This function removes the icon by removing and deleting it from the linked list CSysTrayIcon::NOTIFYICONDATAList
.
4. Demo Project
A class is derived from CSysTrayIcon
with the name CMyAppTrayIcon
. This class overrides only two virtual functions OnLButtonDownDBlClk()
to show a message box and OnRButtonDown
to show a context menu. These two functions get triggered for the Window messages of WM_LBUTTONDBLCLK
and WM_RBUTTONDOWN
respectively, by the routing through a CSysTrayWnd
object.
An object of CMyAppTrayIcon
is kept as an member variable of the CMainFrame
class. Four icons are created in CMainFrame::OnCreate()
. The CMainFrame
class handles all the command handlers for the context menu for the system tray icons.
For context menu processing, the overridden OnRButtonDown
method passes the main window’s pointer to CSysTrayIcon::OnContextMenu
as the third parameter. The main window has the command handlers for the required processing.
void CMyAppTrayIcon::OnRButtonDown(UINT nIconID, CPoint ptMouse) { CMenu t_Menu; t_Menu.LoadMenu(IDR_MAINFRAME); OnContextMenu(t_Menu.GetSubMenu(0), ptMouse, ::AfxGetMainWnd()); }
Use the Icon menu to manipulate the system tray icons as shown the top figure.