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Delphi组件开发-在窗体标题栏添加按钮

发布于: 2012-12-16 15:11:40   |  发布在: Delphi文章   |  点击:

        这是一个在窗体标题栏添加自定义按钮的组件(TTitleBarButton)开发实例,标题栏按钮组件TTitleBarButton以TComponent为直接继承对象,它是一个可以在窗体标题栏上显示按钮的组件,像最大化、最小化和关闭按钮等。

1、首先确定组件的属性。

属性是组件的重要组成部分,它相当于组件的门面,因为一旦一个组件被置于窗体中时,用户必然想到去设置组件的各种属性,编写各种事件的处理过程。TTitleBarButton有以下属性:

Color:用来决定按钮表面的颜色。
Glyph:用来决定按钮表面的图片。
PopupMenu:用来决定右键单击按钮时的弹出菜单。
RightMargin:用来确定按钮的位置,以窗体右边界为基准。
Visible:用来决定按钮是否可见。

2、确定组件的方法。

方法是组件的基本构成部分之一,在编写方法时,尽量减少方法间的依赖关系,并确定方法的可见度,以及是否为虚函数等。在本例中,主要方法如下:
function GetBoundsRect: TRect;   用来确定按钮的边界矩形,可见度为private
procedure NewWndProc(var message: TMessage);  窗体的新的窗口过程,private
procedure Paint; virtual; 该类的继承者可以override该方法,但用户不能直接调该方法
procedure Repaint; 是Paint方法的对外接口,用户可以调用此方法,以强制重新画按钮

3、确定组件的事件。

事件实际上是一种特殊的属性,它也是组件的很重要组成部分,事件为组件响应系统发生的行为而执行的一段代码连接。事件就是方法指针,是方法的触发器。TtitleBarButton只有一个事件:
OnClick事件,用来响应用户的Click事件代码。
 
4、另外,要减少组件的依赖关系。

使一个组件在执行其代码时所受的约束尽可能地少,这是开发组件的一个主要目标,它也是衡量一个组件性能好坏的重要标准之一。 

实现标题栏按钮需要解决以下主要问题:
(1)  如何确定按钮的边界,即Left,Top,Width,Height
通过GetWindowRect来取得窗体的边界矩形,通过GetSystemMetrics取得窗体的框架宽度和标题栏按钮的高度、宽度。再加上RightMargin属性就可以基本上确定按钮的边界了。

(2)  如何画按钮的外观(包括按下和凸起)

通过GetWindowDC来取得窗体DC(包括标题栏、菜单、滚动条等),我们就可以在这个DC上画按钮了。

(3)  如何让按钮响应消息(比如Click,单击右键弹出菜单等)

我们可以通过GetWindowLong取得窗体的窗口过程,然后把我们新定义的窗口过程通过SetWindowLong给这个窗体,然后我们在自己的窗口过程中来让按钮响应消息。

全部代码如下:
unit TitleBarButton;

interface

uses

   Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Menus, Dialogs;

type

  TTitleBarButton = class(TComponent)

  private
    FColor: TColor;
    FGlyph: TBitmap;
    FForm: TCustomForm;
    FOldWndProc: Pointer;
    FButtonDown: Boolean;
    FVisible: Boolean;
    FRightMargin: Cardinal;
    FPopup: TPopupMenu;
    FOnClick: TNotifyEvent;
    procedure SetGlyph(const Value: TBitmap);
    procedure SetVisible(const Value: Boolean);
    procedure SetRightMargin(const Value: Cardinal);
    function GetBoundsRect: TRect;
    procedure NewWndProc(var message: TMessage);

  protected
    procedure Notification(Component: TComponent;Operation: TOperation); override;
    procedure Paint; virtual;

  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure Repaint;
    property BoundsRect: TRect read GetBoundsRect;

  published
    property Color: TColor read FColor write FColor default clBtnFace;
    property Glyph: TBitmap read FGlyph write SetGlyph;
    property PopupMenu: TPopupMenu read FPopup write FPopup;
    property RightMargin: Cardinal read FRightMargin write SetRightMargin default 100;
    property Visible: Boolean read FVisible write SetVisible default False;
    property OnClick: TNotifyEvent read FOnClick write FOnClick;

  end;

procedure Register;

implementation

procedure Register;

begin
  RegisterComponents('Sample', [TTitleBarButton]);
end;

{ TTitleBarButton }

constructor TTitleBarButton.Create(AOwner: TComponent);
var
  ptr: Pointer;
begin
  inherited;
  FForm := GetParentForm(TControl(AOwner));
  FGlyph := TBitmap.Create;
  FColor := clBtnFace;
  FVisible := False;
  FRightMargin := 100;
  FButtonDown := False;
  FOldWndProc := Pointer(GetWindowLong(FForm.Handle,GWL_WNDPROC));
  ptr := MakeObjectInstance(NewWndProc);
  SetWindowLong(FForm.Handle, GWL_WNDPROC, Longint(ptr));
end;

destructor TTitleBarButton.Destroy;
begin
  if not (csDestroying in FForm.ComponentState) then
  begin
    SetVisible(false);
    SetWindowLong(FForm.Handle, GWL_WNDPROC, LongInt(FOldWndProc));
  end;
  FGlyph.Free;
  inherited;
end;

procedure TTitleBarButton.NewWndProc(var message: TMessage);
  function HitButton(APoint: TPoint): Boolean;
  begin
    APoint.x := APoint.x - FForm.Left;
    APoint.y := APoint.y - FForm.Top;
    Result := PtInRect(BoundsRect,APoint);
  end;
var
  p: TPoint;
begin
  with message do
  begin
    if Visible then
    begin
      case Msg of
        WM_NCPAINT , WM_NCACTIVATE :
          begin
            Result := CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
            RePaint;
          end;
        WM_NCHITTEST :
          begin
            Result := CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
            if Result = HTCAPTION then
            begin
              RePaint;
              p.x := LoWord(LParam);
              ScreenToClient(FForm.Handle,p);
              with BoundsRect do                  //减去框架宽度
                if (p.x >= Left-4) and (p.x <= Right-4) then Result := 888;
            end;
          end;
        WM_NCLBUTTONDOWN,WM_NCLBUTTONDBLCLK:
          begin
            Result := CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
            with TWMNCLButtonDown(message) do
              if not HitButton(Point(XCursor, YCursor)) then Exit;
            if WParam = 888 then
            begin
              FButtonDown := True;
              Repaint;
              SetCapture(FForm.Handle);
            end;
          end;
        WM_NCRBUTTONDOWN,WM_NCRBUTTONDBLCLK:
          begin
            if WParam = 888 then
            begin
              if Assigned(FPopup) then
              begin
                p.x := FForm.Left + BoundsRect.Left;
                p.y := FForm.Top + BoundsRect.Bottom;
                FPopup.Popup(p.x,p.y);
              end;
            end
            else
              Result:=CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
          end;
        WM_NCLBUTTONUP,WM_LBUTTONUP :
          begin
            if FButtonDown then
            begin
              FButtonDown := False;
              RePaint;
              ReleaseCapture;
              if Assigned(FOnClick) then FOnClick(self);
            end
            else
              Result:=CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
          end;
        else
          Result := CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
      end;
    end
    else
      Result := CallWindowProc(FOldWndProc,FForm.Handle,Msg,WParam,LParam);
  end;
end;

procedure TTitleBarButton.SetGlyph(const Value: TBitmap);
begin
  FGlyph.Assign(Value);
  SendMessage(FForm.Handle,WM_NCACTIVATE,0,0);
end;

procedure TTitleBarButton.SetRightMargin(const Value: Cardinal);
begin
  FRightMargin := Value;
  SendMessage(FForm.Handle,WM_NCACTIVATE,0,0);
end;

procedure TTitleBarButton.SetVisible(const Value: Boolean);
begin
  FVisible := Value;
  SendMessage(FForm.Handle,WM_NCACTIVATE,0,0);
end;

procedure TTitleBarButton.Notification(Component: TComponent;
  Operation: TOperation);
begin
  inherited;
  if (Operation = opRemove) and (Component = FPopup) then
    FPopup := nil;
end;

function TTitleBarButton.GetBoundsRect: TRect;
var
  Rec: TRect;
  FrameThick: Integer; //窗体框架厚度
  BtnWidth,BtnHeight: Integer; //标题栏按钮的宽度和高度
begin
  GetWindowRect(FForm.Handle,Rec); //得到窗体边界矩形,相对于屏幕左上角
  with Result do
  begin
    FrameThick := GetSystemMetrics(SM_CYFRAME);
    Left := (Rec.Right - Rec.Left) - RightMargin - FrameThick;
    Top := FrameThick;
    if FForm.Borderstyle in [bsSizeToolWin, bsSizeable] then
    begin
      Dec(Left, 2); Inc(Top, 2);
    end
    else begin
      Dec(Left); Inc(Top);
    end;
    if (FForm.Borderstyle in [bsSizeToolWin,bsToolWindow]) then
    begin
      BtnWidth := GetSystemMetrics(SM_CXSMSIZE) - 2;
      BtnHeight := GetSystemMetrics(SM_CYSMSIZE) - 4;
    end
    else begin
      BtnWidth := GetSystemMetrics(SM_CXSIZE) - 2;
      BtnHeight := GetSystemMetrics(SM_CYSIZE) - 4;
    end;
    Right := Left + BtnWidth;
    Bottom := Top + BtnHeight;
  end;
end;

procedure TTitleBarButton.Paint;
var
  GlyphRect: TRect;
begin
  if not FVisible then Exit;
  with TCanvas.Create do
  begin
    try
      Handle := GetWindowDC(FForm.Handle); //得到窗体DC,包括标题栏、菜单、滚动条等
      Brush.Color := FColor;         //画Button凸起和按下时的外观
      if FButtonDown then
        Pen.Color := clBtnHighlight
      else
        Pen.Color := cl3DDkShadow;
      Rectangle(BoundsRect);
      with BoundsRect do
      begin
        if FButtonDown then
          Pen.Color := cl3DDkShadow
        else
          Pen.Color := clBtnHighLight;
        MoveTo(Left,Bottom-2);
        LineTo(Left,Top);
        LineTo(Right-1,Top);
        Pen.Color := clGray;
        if FButtonDown then
        begin
          MoveTo(Left+1,Bottom-3);
          LineTo(Left+1,Top+1);
          LineTo(Right-2,Top+1);
        end
        else begin
          MoveTo(Left+1,Bottom-2);
          LineTo(Right-2,Bottom-2);
          LineTo(Right-2,Top);
        end;
      end;

      if Assigned(Glyph) then      //如果关联了图片,则画图片
      begin
        GlyphRect := BoundsRect;
        GlyphRect.Right := GlyphRect.Right - 7;
        GlyphRect.Bottom := GlyphRect.Bottom - 5;
        if FButtonDown then
          OffsetRect(GlyphRect,4,3)
        else
          OffsetRect(GlyphRect,3,2);
        with GlyphRect do
          StretchBlt(Handle, Left, Top, Right-Left, Bottom-Top,
            FGlyph.Canvas.Handle, 0, 0, FGlyph.Width, FGlyph.Height, srcCopy);
      end;
    finally
      ReleaseDC(FForm.Handle,Handle);
      Free;
    end;
  end;
end;

procedure TTitleBarButton.Repaint;
begin
  Paint;
end;

end.

(本文转载自:http://www.west263.com/www/info/57187-1.htm)

标题栏组件