When using the MDI interface, sometimes you need to display some graphics or software cover in the MDI customer window, so that the software interface will not be empty, the software function can also be at a glance. However, these interfaces are not given directly in Delphi. Putting any graphic control in the MDI form cannot be displayed at runtime. Therefore, the MDI form is required to be modified.
Received:
This program is only for the MDI form. If the application is in a non-MDI form, the consequences are difficult to say, you have tried it.
Remember, the FormStyle property of the form is set to: FSMDIFORM.
solution:
1. Unable to receive the message of the MDI customer window in the MDI main form, so you need to define the processing process of the customer window and take over the MDI customer window (you need to implement it in the overloaded CREATEWND process. ):
Procedure TMDIFORM.CREATEWND;
Begin
inherited;
FNewWndProc: = MakeObjectInstance (ClientWndProc);
FoldWndProc: = Pointer (getWindowlong (ClientHandle, GWL_WNDPROC);
Setwindowlong (ClientHandle, GWL_WndProc, Longint (FNewWndProc);
END;
Among them, ClientWndProc is a custom window process: Procedure ClientWndProc (Var Message: TMessage);
FoldWndProc is used to store pointers in an old window process.
2. Realize your own customer window process:
Procedure TMDIFORM.CLIENTWNDPROC (Var Message: TMESSAGE);
VAR
R: TRECT;
PROCEDURE DEFAULT;
Begin
WITH MESSAGE DO
Result: = CallWindowProc (FoldwndProc, ClientHandle, MSG, WPARAM, LPARAM);
END;
VAR
PS: tpaintstruct;
Begin
R: = ClientRect;
Case message.msg of
WM_PAINT:
Begin
BeginPaint (ClientHandle, PS);
Try
Canvas.lock;
Try
Canvas.handle: = ps.hdc;
Try
Paint;
IF controlcount> 0 THEN
PaintControls (ps.hdc, controls [0]);
Finally
Canvas.Handle: = 0;
END;
Finally
Canvas.unlock;
END;
Finally
Endpaint (ClientHandle, PS);
END;
END;
WM_ERASEBKGND:
Begin
Drawbg (twmesebkgnd (message) .dc);
Message.Result: = 1;
END;
WM_VSCROLL, WM_HSCROLL:
Begin
INVALIDATERECT (ClientHandle, @ r, true);
DEFAULT;
END;
WM_SIZE:
Begin
INVALIDATERECT (ClientHandle, @ r, true);
DEFAULT;
END;
Else
DEFAULT;
END;
END;
The above DRAWBG is used to draw a window background.
3. Implement the window background.
In order to allow the successor to define the background, this process shows Virtual:
protected
Procedure DrawBG (DC: HDC); Virtual;
Here, the drawbg process is just a simple fill window background:
Procedure TMDIFORM.DRAWBG (DC: HDC);
Begin
IF brush.color <> clnone dam
FillRect (DC, ClientRect, brush.handle);
END;
4. In summary, summarizing the TMDIFROM class is as follows:
TMDIFORM = Class (TFORM)
Private
FoldWndProc: tfarproc;
FNewWndproc: TfarProc;
Procedure ClientWndProc (var message: tMessage);
protected
Procedure DrawBG (DC: HDC); Virtual;
PROCEDURE CREATEWND; OVERRIDE;
END;
5. After the above transformation, you can draw the designated background in DrawBG (you need to call the Windows GUI interface directly), or use the graphic control directly, or the onpaint event of the form, the MDI window has a colorful.
