PostMessage() any ideas

[bluelocust]

I am writing a vb program that utilizes two separate applications. One is the user interface and display the other is for data acquisition through usb. To communicate between the two applications I would like to use the PostMessage() API.

I am having trouble understanding how the application interprets the message. I read an article for closing an application that had the sample code below:

Declare Function FindWindow Lib "user32" Alias _
"FindWindowA" (ByVal lpClassName As String, _
ByVal lpWindowName As String) As Long
Declare Function PostMessage Lib "user32" Alias _
"PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
ByVal wParam As Long, lParam As Any) As Long


Sub CloseProgram()

Dim winHwnd As Long
Dim RetVal As Long
Const WM_CLOSE = &H10

winHwnd = FindWindow(vbNullString, "Calculator")
If winHwnd <> 0 Then
RetVal = PostMessage(winHwnd, WM_CLOSE, 0&, 0&)
End If

End Sub

So here is the question. The Const WM_CLOSE = &H10, how do you come up with &H10? Are the standard WM_ values defined somewhere? I am not interested specifically the WM_CLOSE but all of the WM_ messages.

Also is there a way to define your own WM_ and have the other application respond.

Anyone have any answers.

Messages, Constants and Structures (called Types in VB) are listed in the API Text Viewer.

Start > Programs > Microsoft Visual Basic > API Text Viewer.

Once you are in it, go to File > Load TextFile and select Win32API.txt. In the API Type ComboBox, select Constants and you'll be given a list of constants.

[bluelocust]

What about defining your own WM_? Say I wanted to pause a timer in another application. How could I
RetVal = PostMessage(winHwnd, WM_PauseTimer1, 0&, 0&)?

WM_? are just constants for different messages. To write your own, you would have to define the constant in a DLL file and write it's prodecure up yourself.

[kedaman]

Yep, i think you can define whatever messages you want, it's only the number that will be passed, not the WM_...

WM_MessageToBluelocust=&H1000000

The problems is that you have to find a number that does not interfer with the window messages, for instance WM_CLOSE.