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其中部分程序如下
{
Copyright ?1998 by Delphi 4 Developer's Guide - Xavier Pacheco and Steve Teixeira
}
unit MainFrm;
interface
uses Windows, SysUtils, Classes, Graphics, Forms, Controls, Menus,
StdCtrls, Dialogs, Buttons, Messages, ExtCtrls;
type
TMainForm = class(TForm)
mmMain: TMainMenu;
mmiFile: TMenuItem;
mmiNew: TMenuItem;
mmiClose: TMenuItem;
N1: TMenuItem;
mmiExit: TMenuItem;
mmiImage: TMenuItem;
mmiTile: TMenuItem;
mmiCenter: TMenuItem;
mmiStretch: TMenuItem;
imgMain: TImage;
procedure mmiNewClick(Sender: TObject);
procedure mmiCloseClick(Sender: TObject);
procedure mmiExitClick(Sender: TObject);
procedure mmiTileClick(Sender: TObject);
private
FOldClientProc,
FNewClientProc: TFarProc;
FDrawDC: hDC;
procedure CreateMDIChild(const Name: string);
procedure ClientWndProc(var Message: TMessage);
procedure DrawStretched;
procedure DrawCentered;
procedure DrawTiled;
protected
procedure CreateWnd; override;
end;
var
MainForm: TMainForm;
implementation
uses MdiChildFrm;
{$R *.DFM}
procedure TMainForm.CreateWnd;
begin
inherited CreateWnd;
// Turn the ClientWndProc method into a valid window procedure
FNewClientProc := MakeObjectInstance(ClientWndProc);
// Get a pointer to the original window procedure
FOldClientProc := Pointer(GetWindowLong(ClientHandle, GWL_WNDPROC));
// Set ClientWndProc as the new window procedure
SetWindowLong(ClientHandle, GWL_WNDPROC, LongInt(FNewClientProc));
end;
procedure TMainForm.DrawCentered;
{ This procedure centers the image on the form's client area }
var
CR: TRect;
begin
GetWindowRect(ClientHandle, CR);
with imgMain do
BitBlt(FDrawDC, ((CR.Right - CR.Left) - Picture.Width) div 2,
((CR.Bottom - CR.Top) - Picture.Height) div 2,
Picture.Graphic.Width, Picture.Graphic.Height,
Picture.Bitmap.Canvas.Handle, 0, 0, SRCCOPY);
end;
procedure TMainForm.DrawStretched;
{ This procedure stretches the image on the form's client area }
var
CR: TRect;
begin
GetWindowRect(ClientHandle, CR);
StretchBlt(FDrawDC, 0, 0, CR.Right, CR.Bottom,
imgMain.Picture.Bitmap.Canvas.Handle, 0, 0,
imgMain.Picture.Width, imgMain.Picture.Height, SRCCOPY);
end;
procedure TMainForm.DrawTiled;
{ This procedure tiles the image on the form's client area }
var
Row, Col: Integer;
CR, IR: TRect;
NumRows, NumCols: Integer;
begin
GetWindowRect(ClientHandle, CR);
IR := imgMain.ClientRect;
NumRows := CR.Bottom div IR.Bottom;
NumCols := CR.Right div IR.Right;
with imgMain do
for Row := 0 to NumRows+1 do
for Col := 0 to NumCols+1 do
BitBlt(FDrawDC, Col * Picture.Width, Row * Picture.Height,
Picture.Width, Picture.Height, Picture.Bitmap.Canvas.Handle,
0, 0, SRCCOPY);
end;
procedure TMainForm.ClientWndProc(var Message: TMessage);
begin
case Message.Msg of
// Capture the WM_ERASEBKGND messages and perform the client area drawing
WM_ERASEBKGND:
begin
CallWindowProc(FOldClientProc, ClientHandle, Message.Msg, Message.wParam,
Message.lParam);
FDrawDC := TWMEraseBkGnd(Message).DC;
if mmiStretch.Checked then
DrawStretched
else if mmiCenter.Checked then
DrawCentered
else DrawTiled;
Message.Result := 1;
end;
{ Capture the scrolling messages and ensure the the client area
is redrawn by calling InvalidateRect }
WM_VSCROLL, WM_HSCROLL:
begin
Message.Result := CallWindowProc(FOldClientProc, ClientHandle, Message.Msg,
Message.wParam, Message.lParam);
InvalidateRect(ClientHandle, nil, True);
end;
else
// By Default, call the original window procedure
Message.Result := CallWindowProc(FOldClientProc, ClientHandle, Message.Msg,
Message.wParam, Message.lParam);
end; { case }
end;
procedure TMainForm.CreateMDIChild(const Name: string);
var
MdiChild: TMDIChildForm;
begin
MdiChild := TMDIChildForm.Create(Application);
MdiChild.Caption := Name;
end;
procedure TMainForm.mmiNewClick(Sender: TObject);
begin
CreateMDIChild('NONAME' + IntToStr(MDIChildCount + 1));
end;
procedure TMainForm.mmiCloseClick(Sender: TObject);
begin
if ActiveMDIChild <> nil then
ActiveMDIChild.Close;
end;
procedure TMainForm.mmiExitClick(Sender: TObject);
begin
Close;
end;
procedure TMainForm.mmiTileClick(Sender: TObject);
begin
mmiTile.Checked := false;
mmiCenter.Checked := False;
mmiStretch.Checked := False;
{ Set the Checked property for the menu item which invoked }
{ this event handler to Checked }
if Sender is TMenuItem then
TMenuItem(Sender).Checked := not TMenuItem(Sender).Checked;
{ Recraw the client area of the form }
InvalidateRect(ClientHandle, nil, True);
end;
end.
