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Article #17157: Broadcast a message

 Question and Answer Database

FAQ2157C.txt   Broadcast a message
Category   :Windows API
Platform    :All
Product    :C++Builder  1.x

Question:
How do I broadcast a message to all top level Windows?

Answer:
The  Windows API function SendMessage()  takes a 4 parameters. The
first is the window handle. To broadcast to all top level Windows, use
HWND_BROADCAST. The second parameter is the message itself, and then
the WParam and the LParam parameters for the given message. For the
WM_WININICHANGE message, wParam should be zero, and LParam should be
either the address of a null terminated section name that changed, or
nil if you want each window to examine all sections for the change.
Passing a null value is not recommended unless you have modified several
sections due to performance considerations.

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    char s[64];
    StrCopy(s, "windows");
    SendMessage(HWND_BROADCAST, WM_WININICHANGE, 0, long(&s));
}

7/2/98 10:32:32 AM
 

Last Modified: 01-SEP-99