Add Your Application's Icon to the System Tray

You can add your application's icon to the system tray, the small area on the right side of the task bar, and react to mouse events occurring on your system tray icon. In this sample I display a message but you can just as easily popup a menu.

I also show you how to create an instance of an ActiveX object and call one of its methods when the user right clicks on the icon in the system tray. Normally it is not possible to instantiate objects from the tray due to the way Windows handles Remote Procedure Calls. However, you can do it by executing your object code from a timer event.

Add your application's icon to the system tray and respond to mouse events.
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Add you App's Icon to the System Tray and Respond to Mouse Events

The Shell_NotifyIcon API function sends a message to the system to add, modify, or delete an icon from the taskbar status area and is the basis of this program.

When you click the Add button, a NOTIFYICONDATA structure is populated. This structure contains the information needed to place your icon in the system tray. Its hWnd element gets assigned the handle of your form that will receive the notification messages when a mouse event occurs to the system tray icon. Its uID element should be set to your form's icon property and its hIcon value to the handle of the icon to add, delete or modify. The uCallbackMessage element should be set to the system message that will be sent to the form specified by hWnd whenever a mouse event occurs to the tray icon. Typically the WM_MOUSEMOVE message is specified.

You can have a tool tip message display when the mouse hovers over the tray icon. To do this you need to add the text to the szTip element. Once these values are set, the uFlags item needs to be set to NIF_ICON Or NIF_MESSAGE Or NIF_TIP to indicate that all values contain valid data.

A call to Shell_NotifyIcon passing the NotifyIconData strucutre and the NIM_ADD flag adds your icon to the system tray. Now, whenever a mouse action occurs over the icon, your form's MouseMove event will fire and its X parameter will receive a value from the system. By decoding this value, you can tell what the mouse action was. For example, left button up, right button up, left button double clicked,.... In this sample, on a left button up action I display a message.

Before your application terminates it should remove the icon from the tray. Again just call Shell_NotifyIcon passing it the same NotifyIconData. This time, however, send the NIM_DELETE message.

Working With an ActiveX Object

When your form's MouseMove procedure triggers due to a mouse event on your system tray icon you can execute any code that you would normally call from MouseMove -- almost. If you need to call CreateObject to create a new instance of an ActiveX component or read a property or execute a method from an existing component, you will get an error message. This is due to the way Windows handles Remote Procedure Calls from the status area.

What you need to do is enable a timer from the MouseMove procedure. The timer's interval should be set to a low value so it fires immediately. Place your code to instantiated or work with the ActiveX component in the timer event and when the timer goes off your code will run without any RPC errors. Remember to disable the timer as soon as it fires.

The SystemTray project issues a CreateObject to create an instance of the Sample component I have included. Sample is a very basic out of process ActiveX component containing a single class and a single method. All it does is display a messagebox. But the idea is to illustrate how to call it from the system tray.

Instructions

Download the code. Run the Sample.vbp project by pressing Ctrl-F5 or compile it to create Sample.exe. Without this code running or the .Exe available, an error will occur when you right click on the icon in the system tray.

Now run the SystemTray project. Click the Add button to place the Globe icon in the system tray. Left click on the Globe to display a message. Right click the Globe to display a message from the Sample ActiveX code component.


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