在Delphi中如何实现VC中的CRectTracker类

Question

在Delphi中如何实现VC中的CRectTracker类,就是在作图时用鼠标画一个圆或是一个矩形
后用鼠标可以拖放它的位置和大小。

Answer 1

鼠标移动前先SetCapture一下就行了。

Answer 2

我以前写过一个，但代码找不到了，给你一个橡皮条拉拉吧！可能会用的到。
unit TrackerBand;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}
type
  TDrawFlag = (dfToDraw,dfDrawing,dfDrawn);
var
  TrackerBrush: TBrush = Nil;
  TrackerPen: TPen = Nil;
  HalfToneBrush:TBrush = Nil;
  OldDragRect: TRect = (Left:0;Top:0;Right:0;Bottom:0);
procedure InitHalfToneBrush;
var grayPattern:array[0..7] of WORD;
    grayBitmap:HBITMAP;
    I:Integer;
begin
  if HalfToneBrush = Nil then
  begin
    HalfToneBrush := TBrush.Create;
    for I := 0 to 7 do
      grayPattern[i] := WORD(($5555 shl (I and 1)));
    grayBitmap := Windows.CreateBitmap(8, 8, 1, 1, @grayPattern);
    if (grayBitmap <> 0) then
    begin
      HalftoneBrush.Handle := Windows.CreatePatternBrush(grayBitmap);
      Windows.DeleteObject(grayBitmap);
    end;
  end;
end;procedure DrawDragRect(DC:HDC;NewRect:TRect;DragFlag:TDrawFlag;BandWidth:Integer = 3);
var rgnNew,rgnOld,rgnTemp:HRGN;
    SaveIndex: Integer;
    TempRect: TRect;
begin
  SaveIndex := Windows.SaveDC(DC);
  try
    { Get the region which is the old border }
    if DragFlag = dfToDraw then rgnOld := 0
    else begin
      TempRect := OldDragRect;
      rgnTemp := Windows.CreateRectRgnIndirect(TempRect);
      Windows.InflateRect(TempRect,BandWidth,BandWidth);
      rgnOld := Windows.CreateRectRgnIndirect(TempRect);
      Windows.CombineRgn(rgnOld,rgnOld,rgnTemp,RGN_XOR);
      Windows.DeleteObject(HRGN(rgnTemp));
    end;    { Get the region which is the new border }
    if DragFlag = dfDrawn then  rgnNew := 0
    else begin
      TempRect := NewRect;
      //RectNormalize(TempRect);
      OldDragRect := TempRect;
      rgnTemp := Windows.CreateRectRgnIndirect(TempRect);
      Windows.InflateRect(TempRect,BandWidth,BandWidth);
      rgnNew := Windows.CreateRectRgnIndirect(TempRect);
      Windows.CombineRgn(rgnNew,rgnNew,rgnTemp,RGN_XOR);
      Windows.DeleteObject(HRGN(rgnTemp));
    end;    { Get the different region between new and old }
    if rgnNew = 0 then rgnNew := Windows.CreateRectRgn(0,0,0,0);
    Windows.CombineRgn(rgnNew,rgnNew,rgnOld,RGN_XOR);    { Draw into the border region which need to be updated }
    Windows.SelectClipRgn(DC,rgnNew);
    Windows.GetClipBox(DC,TempRect);
    Windows.SelectObject(DC,HalfToneBrush.Handle);
    with TempRect do
      Windows.PatBlt(DC,Left,Top,Right-Left,Bottom-Top,PATINVERT);    if rgnOld <> 0 then Windows.DeleteObject(HRGN(rgnOld));
    if rgnNew <> 0 then Windows.DeleteObject(HRGN(rgnNew));    { Remove the clip region }
    Windows.SelectClipRgn(DC,0);
  finally
    Windows.RestoreDC(DC,SaveIndex);
  end;
end;
procedure InitGlobalObjects;
var
  HatchPattern: Array[0..7] of WORD;
  WPattern: WORD;
  I: Integer;
  HatchBitmap:HBITMAP;
begin
  WPattern := $1111;
  if TrackerBrush = Nil then
  begin
    TrackerBrush := TBrush.Create;
    {Create the hatch pattern + bitmap}
    for I := 0 to 3  do
    begin
      HatchPattern[i] := WPattern;
      HatchPattern[i+4] := WPattern;
      WPattern := WPattern shl 1;
    end;    HatchBitmap := Windows.CreateBitmap(8, 8, 1, 1, @HatchPattern);
    if HatchBitmap <> 0 then
    begin
      { Create black hatched brush }
      TrackerBrush.Handle := Windows.CreatePatternBrush(HatchBitmap);
      Windows.DeleteObject(HatchBitmap);
    end;    if TrackerPen = Nil then
    begin
      TrackerPen := TPen.Create;
      {create black dotted pen}
      TrackerPen.Handle := CreatePen(PS_DOT, 0, RGB(0, 0, 0));
    end;
  end;  InitHalfToneBrush;
  OldDragRect := Rect(0,0,0,0);
end;procedure ReleaseGlobalObjects;
begin
  if HalfToneBrush  <> Nil then  HalfToneBrush.Free;
  if TrackerBrush <> Nil then  TrackerBrush.Free;
  if TrackerPen <> Nil then  TrackerPen.Free;
end;procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  DrawDragRect(Canvas.Handle,Rect(X,Y,X,Y),dfToDraw,4);
end;procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if ssLeft in Shift then
  DrawDragRect(Canvas.Handle,Rect(OldDragRect.Left,OldDragRect.Top,X,Y),dfDrawing,4);
end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  DrawDragRect(Canvas.Handle,Rect(OldDragRect.Left,OldDragRect.Top,X,Y),dfDrawn,4);
end;Initialization
  InitGlobalObjects;
finalization
  ReleaseGlobalObjects;end.