开发圆角Panel的问题，老闪！

Question

我写了个圆角的panel组件，重绘的时候会一直闪烁，设计期和运行期都是如此，请大家看看！
这是Paint事件
procedure TRoundPanel.Paint;
var
  rect:TRect;
  i:integer;
  tmpPS:PAINTSTRUCT;
  myHDC:HDC;
begin
  if FRoundPanel then
    begin
    rect:=self.ClientRect;
    myHDC:=BeginPaint(Handle,tmpPS);
    for i:=5 downto 1 do
    begin
      canvas.Pen.Color:= BaseColor+FStepColor;
      canvas.RoundRect(rect.Left+i,rect.Top+i,rect.Right-i,rect.Bottom-i,FRoundWidth,FRoundHeight);
    end;
    RoundClientArea;
    EndPaint(Handle,tmpPS);
  end;
  inherited Paint;
end;
//是下面这个事件导致闪烁
procedure TRoundPanel.RoundClientArea;
var
  rect:Trect;
  rgn:Hrgn;
begin
  rect:=self.ClientRect;
  Rgn:=CreateRoundRectRgn(rect.Left,rect.Top,rect.Right,rect.Bottom,FRoundWidth,FRoundHeight);
  setWindowRgn(self.Handle,rgn,true);（是这个语句导致的）
end;

Answer 1

你的Paint方法调用了RoundClientArea;
而RoundClientArea调用了setWindowRgn(self.Handle,rgn,true);
而setWindowRgn的第三个参数为True,所以它立刻重绘,于是Paint方法又被调用.....这样就处于不停的重绘状态了

Answer 2

{曲线化控件}procedure MakeRound(mControl: TWinControl; Width, height: integer; style: byte);
var
  Rgn: HRGN;
  left, top, right, bottom: integer;
begin
  top := -height;
  left := -width;
  right := mControl.BoundsRect.Right + width;
  bottom := mControl.BoundsRect.bottom + height;
  if (style and 1) > 0 then
  begin
    top := top + height;
    left := left + width;
  end;
  if (style and 2) > 0 then
  begin
    if (style and 1) = 0 then
      left := left + width;
    bottom := bottom - height;
  end;
  if (style and 4) > 0 then
  begin
    if (style and 2) = 0 then
      bottom := bottom - height;
    right := right - width;
  end;
  if (style and 8) > 0 then
  begin
    if (style and 4) = 0 then
      right := right - width;
    if (style and 1) = 0 then
      top := top + height;
  end;
  Rgn := CreateRoundRectRgn(left, top, right, bottom, Width, height);
  SetWindowRgn(mControl.Handle, rgn, true);
end;

Answer 3

setWindowRgn(self.Handle,rgn,true)这句话的第3个参数即使改为false也不行，同样的问题。
我把源代码贴出来大家共同探讨一下。其实我觉得写过控件的应该觉得很简单。unit RoundPanel;interfaceuses
  SysUtils, Classes, Controls, ExtCtrls,graphics,windows,messages,Themes;type
  TRoundPanel = class(TPanel)
  private
    FStepColor:int64;
    FBaseColor:TColor;
    FRoundPanel:boolean;
    FRoundWidth:integer;
    FRoundHeight:integer;
    procedure SetStepColor(StepColor:int64);
    procedure SetBaseColor(BaseColor:TColor);
    procedure SetRoundPanel(RoundPanel:boolean);
    procedure SetRoundWidth(RoundWidth:integer);
    procedure SetRoundHeight(RoundHeight:integer);
    procedure RoundClientArea;
  protected
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd);
        message WM_ERASEBKGND;
    procedure Paint;override;
  public
    procedure PaintRound;
    constructor Create(AOwner: TComponent);override;
  published
    property StepColor:int64 read FStepColor Write SetStepColor  default 1000000;
    property BaseColor:TColor read FBaseColor write SetBaseColor default clBtnFace;
    property RoundPanel:boolean read FRoundPanel Write SetRoundPanel default false;
    property RoundWidth:integer read FRoundWidth write SetRoundWidth default 0;
    property RoundHeight:integer read FRoundHeight write SetRoundHeight default 0;
  end;procedure Register;implementationprocedure Register;
begin
  RegisterComponents('Samples', [TRoundPanel]);
end;constructor TRoundPanel.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);end;procedure TRoundPanel.Paint;
var
  rect:TRect;
  i:integer;
  tmpPS:PAINTSTRUCT;
  myHDC:HDC;
begin
  inherited Paint;
  if FRoundPanel then
    begin
    rect:=self.ClientRect;
    myHDC:=BeginPaint(Handle,tmpPS);
    for i:=5 downto 1 do
    begin
      canvas.Pen.Color:= BaseColor+FStepColor;
      canvas.RoundRect(rect.Left+i,rect.Top+i,rect.Right-i,rect.Bottom-i,FRoundWidth,FRoundHeight);
    end;
    //RoundClientArea;
    EndPaint(Handle,tmpPS);
  end;end;procedure TRoundPanel.SetStepColor(StepColor:int64);
begin
  FStepColor:=StepColor;
end;procedure TRoundPanel.SetBaseColor(BaseColor:TColor);
begin
  FBaseColor:=BaseColor;
end;procedure TRoundPanel.SetRoundPanel(RoundPanel:boolean);
begin
  FRoundPanel:=RoundPanel;
end;procedure TRoundPanel.SetRoundWidth(RoundWidth:integer);
begin
  FRoundWidth:=RoundWidth;
end;procedure TRoundPanel.SetRoundHeight(RoundHeight:integer);
begin
  FRoundHeight:=RoundHeight;
end;procedure TRoundPanel.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
    Message.Result := 0;
end;procedure TRoundPanel.RoundClientArea;
var
  rect:Trect;
  rgn:Hrgn;
begin
  rect:=self.ClientRect;
     Rgn:=CreateRoundRectRgnrect.Left,rect.Top,rect.Right,rect.Bottom,FRoundWidth,FRoundHeight);
  setWindowRgn(self.Handle,rgn,false);
end;procedure TRoundPanel.PaintRound;
begin
  RoundClientArea;
  paint;
end;end.
希望高手们给出具体点的建议来！

Answer 4

这样开发出来的也不是圆角 Panel 啊，其实只要用
var
HT: THandle;HT := CreateRoundRectRgn(0, 0, Width, Height, RX, RY);//RX，RY就是圆角控制，integer；SetWindowRgn(Handle, HT, True);然后用 Pen 的大小来描一下边框就很好了。不用那么复杂；以上纯属个人之见！！

Answer 5

应该在Panel的OnResize事件中SetWindowRgn

Answer 6

这东西做成控件没有多大的意义，还不如像 ahjoe(强哥) 所说的那样做