␡
- Introduction
- Message Handling: Not "Contract Free"
- Assigning Message Result Values
- The TApplication Type's OnMessage Event
Like this article? We recommend
Like this article? We recommend
Like this article? We recommend
Like this article? We recommend
Assigning Message Result Values
When you handle some Windows messages, Windows expects you to return a result value. The classic example is the WM_CTLCOLOR message. When you handle this message, Windows expects you to return a handle to a brush with which you want Windows to paint a dialog box or control. (Delphi provides a Color property for components that does this for you, so the example is just for illustration purposes.) You can return this brush handle easily with a message-handling procedure by assigning a value to the Result field of TMessage (or another message record) after calling inherited. For example, if you were handling WM_CTLCOLOR, you could return a brush handle value to Windows with the following code:
procedure TForm1.WMCtlColor(var Msg: TWMCtlColor);
var
BrushHand: hBrush;
begin
inherited;
{ Create a brush handle and place into BrushHand variable }
Msg.Result := BrushHand;
end;