WindowFromPoint API Example

Category:

System/API

Type:

Snippets

Difficulty:

Intermediate

Author:

Basharat Ali

Version Compatibility:

More information:

This code demonstrates how to use the WindowFromPoint API, which returns a handle to a window (whether or not the window is within your application) when the mouse cursor is passed over it. In this particular demo, the window's class name is displayed, but as explained in the comments, there are many other things you can do with a window once you have its handle. The comments also explain how to get the demo running.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
Option Explicit Private Declare Function GetCursorPos Lib "user32" _ (lpPoint As POINTAPI) As Long Private Declare Function WindowFromPoint Lib "user32" (ByVal _ xpoint As Long, ByVal ypoint As Long) As Long Private Declare Function GetClassName Lib "user32" Alias _ "GetClassNameA" (ByVal hwnd As Long, ByVal lpClass _ As String, ByVal nMaxCount As Long) As Long Private Type POINTAPI X As Long Y As Long End Type Private gStop As Boolean Private prevWindow As Long, curWindow As Long Private X As Long, Y As Long Private className As String Private retValue As Long Private mousePT As POINTAPI

Code:

'****************************
'*PURPOSE: DEMONSTRATE HOW TO USE WINDOWFROMPOINTAPI TO
'          OBTAIN A HANDLE TO THE WINDOW THE CURSOR IS OVER.
'*
'*TO USE:  1) Create a New Exe Project
'*         2) Add a timer to the form (Timer1).  Set Interval
'*            to 1 and Enabled to True
'*         3) Add a label to the form (Label1). Set 
'*            AutoSize property to True
'*
'*         The label will display the class name of the window
'*         This is one of the many things you can do with a 
'*         window's handle. In other words, you can modify this
'*         code to close the window, close its parent process,
'*         get the window's text, etc.  There are many examples
'*         of such techniques on http://www.freevbcode.com

Private Sub Timer1_Timer()

gStop = False
prevWindow = 0
Do
    If gStop = True Then Exit Do
    Call GetCursorPos(mousePT)
    X = mousePT.X
    Y = mousePT.Y
    curWindow = WindowFromPoint(X, Y)
    If curWindow <> prevWindow Then
        className = String$(256, " ")
        prevWindow = curWindow
        retValue = GetClassName(curWindow, className, 255)
        className = Left$(className, InStr(className, _
            vbNullChar) - 1)
            If className = "SysListView32" Then
             Label1.Caption = "the mouse is over the desktop. "
            Else
               Label1.Caption = "the mouse is over " & className
            End If
    End If
          DoEvents
 Loop
End Sub