1. GetMessageExtraInfo
The GetMessageExtraInfo function retrieves the extra message information for the current thread. Extra message information is an application- or driver-defined value associated with the current thread's message queue.
Syntax
LPARAM GetMessageExtraInfo(VOID);
Return Value
The return value specifies the extra information. The meaning of the extra information is device specific.
Remarks
To set a thread's extra message information, use the SetMessageExtraInfo function.
2. SetMessageExtraInfo
The SetMessageExtraInfo function sets the extra message information for the current thread. Extra message information is an application- or driver-defined value associated with the current thread's message queue. An application can use the GetMessageExtraInfo function to retrieve a thread's extra message information.
Syntax
LPARAM SetMessageExtraInfo( LPARAM lParam);
Parameters
lParam
[in] Specifies the value to associate with the current thread.
Return Value
The return value is the previous value associated with the current thread.
实例：
1 unit Unit1; 2 3 interface 4 5 uses 6 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, 7 StdCtrls; 8 9 {define an application specific user message} 10 const 11 UserMessage = WM_USER+1; 12 13 type 14 TForm1 = class(TForm) 15 Button1: TButton; 16 procedure Button1Click(Sender: TObject); 17 private 18 { Private declarations } 19 public 20 {the handler for our user message} 21 procedure DoMessage(var Msg: TMessage); message UserMessage; 22 end; 23 24 var 25 Form1: TForm1; 26 27 implementation 28 29 {$R *.DFM} 30 31 procedure TForm1.Button1Click(Sender: TObject); 32 begin 33 {set the message extra information} 34 SetMessageExtraInfo(12345); 35 36 {send the user message to the window} 37 Perform(UserMessage, 0, 0); 38 end; 39 40 procedure TForm1.DoMessage(var Msg: TMessage); 41 begin 42 {the user message was retrieved, show the message extra info} 43 Button1.Caption := 'User Message Received. Info: '+ 44 IntToStr(GetMessageExtraInfo); 45 end; 46 47 end.
