请问高手，如何使panel变成透明的？谢谢！

reanna 2003-11-19 12:17:16

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Spring414 2003-12-29

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不可以写些代码，让原生的Panel变透明吗？

angelior 2003-12-29

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angelior 2003-12-29

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Panel透明
unit Glass;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ExtCtrls;

type
TGlassStyle = (
gsBlackness, gsDstInvert, gsMergeCopy, gsMergePaint, gsNotSrcCopy,
gsNotSrcErase, gsPatCopy, gsPatInvert, gsPatPaint, gsSrcAnd,
gsSrcCopy, gsSrcErase, gsSrcInvert, gsSrcPaint, gsWhiteness);

TGlass = class(TCustomControl)
private
FColor: TColor;
FStyle: TGlassStyle;
FOnPaint: TNotifyEvent;

procedure SetColor(Value: TColor);
procedure SetStyle(Value: TGlassStyle);
procedure CMCtl3DChanged(var Message: TMessage); message CM_CTL3DCHANGED;
procedure WMEraseBkgnd(var Message: TMessage); message WM_ERASEBKGND;
procedure WMWindowPosChanging(var Message: TWMWindowPosChanging); message WM_WINDOWPOSCHANGING;
protected
Buffer: TBitmap;

procedure CreateParams(var Params: TCreateParams); override;
procedure Paint; override;
procedure Resize; override;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
property Canvas;
published
property Align;
property Anchors;
property AutoSize;
property BiDiMode;
property BorderWidth;
property Color: TColor read FColor write SetColor;
property Ctl3D;
property Enabled;
property Style: TGlassStyle read FStyle write SetStyle default gsSrcAnd;
property Visible;

property OnClick;
property OnDblClick;
property OnEnter;
property OnExit;
property OnMouseDown;
property OnMouseMove;
property OnMouseUp;
property OnResize;
property OnPaint: TNotifyEvent read FOnPaint write FOnPaint;
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('Croco', [TGlass]);
end;

function GlassStyleToInt(gs: TGlassStyle): LongInt;
begin
case gs of
gsBlackness : Result := cmBlackness;
gsDstInvert : Result := cmDstInvert;
gsMergeCopy : Result := cmMergeCopy;
gsMergePaint : Result := cmMergePaint;
gsNotSrcCopy : Result := cmNotSrcCopy;
gsNotSrcErase: Result := cmNotSrcErase;
gsPatCopy : Result := cmPatCopy;
gsPatInvert : Result := cmPatInvert;
gsPatPaint : Result := cmPatPaint;
gsSrcAnd : Result := cmSrcAnd;
gsSrcCopy : Result := cmSrcCopy;
gsSrcErase : Result := cmSrcErase;
gsSrcInvert : Result := cmSrcInvert;
gsSrcPaint : Result := cmSrcPaint;
gsWhiteness : Result := cmWhiteness;
else Assert(True, 'Error parameter in function GlassStyleToInt');
end;
end;

constructor TGlass.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
Buffer := TBitmap.Create;

ControlStyle := [csAcceptsControls, csCaptureMouse, csClickEvents,
csDoubleClicks, csReplicatable];
Width := 100;
Height := 100;
FStyle := gsSrcAnd;
ParentCtl3d := False;
Ctl3D := False;
ParentColor := False;
FColor := clWhite;
end;

destructor TGlass.Destroy;
begin
Buffer.Free;
inherited Destroy;
end;

procedure TGlass.Paint;
var
R: TRect;
rop: LongInt;
begin
R := Rect(0, 0, Width, Height);
Buffer.Width := Width;
Buffer.Height := Height;
Buffer.Canvas.Brush.Style := bsSolid;
Buffer.Canvas.Brush.Color := FColor;
Buffer.Canvas.FillRect(Rect(0, 0, Width, Height));
rop := GlassStyleToInt(FStyle);
StretchBlt(Buffer.Canvas.Handle, 0, 0, Width, Height,
Canvas.Handle, 0, 0, Width, Height, rop);
if Ctl3D then DrawEdge(Buffer.Canvas.Handle, R, BDR_RAISEDINNER, BF_RECT);
Buffer.Canvas.Pen.Mode := pmCopy;
Buffer.Canvas.Pen.Style := psSolid;
Canvas.Draw(0, 0, Buffer);
if Assigned(FOnPaint) then FOnPaint(Self);
end;

procedure TGlass.SetColor(Value: TColor);
begin
if Value <> FColor then
begin
FColor := Value;
RecreateWnd;
end;
end;

procedure TGlass.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);

Params.ExStyle := Params.ExStyle + WS_EX_TRANSPARENT;
end;

procedure TGlass.WMWindowPosChanging(var Message: TWMWindowPosChanging);
begin
Invalidate;

inherited;
end;

procedure TGlass.WMEraseBkgnd(var Message: TMessage);
begin
Message.Result := 0;
end;

procedure TGlass.Resize;
begin
Invalidate;

inherited;
end;

procedure TGlass.CMCtl3DChanged(var Message: TMessage);
begin
inherited;

RecreateWnd;
end;

procedure TGlass.SetStyle(Value: TGlassStyle);
begin
if Value <> FStyle then
begin
FStyle := Value;
RecreateWnd;
end;
end;

end.

lxhong1980 2003-11-19

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hongqi162 2003-11-19

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使panel自身变成透明:
如果自己做个控件继承自TPanel的话比较容易:
1. override createparams方法:
procedure CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(params);
Params.exstyles := Params.exstyles or WS_EX_TRANSPARENT; // 设置为透明窗
end;

2. 截取WM_ERASEBKGND消息.
procedure WMEraseBkgnd(var Message: TMessage);
begin
Message.result := 1; // 什么都不做既返回. panel默认的erasebkgnd将
// fillrect, 所以需要去掉它
end;
3. 最重要的一步: 需要通过SetWindowLong修改parent control的style:
procedure SetParentStyle;
begin
SetWindowLong(Parent.Handle, GWL_STYLE,
GetWindowLong(Parent.Handle, GWL_STYLE) and
not WS_CLIPCHILDREN);
// 如果没有这步, parent在repaint时不会画上被当前panel遮住的部分. 不过在
// 第一次建立时也能取到背景, 不过不是parent的图案, 而是透明到Desktop上去了,
// 显示的是当前Desktop上的图案, 效果就象在你的form上挖了个洞.
RecreateWnd; // 重建当前panel的handle, 系统将自动重画, 这时panel的
// 背景已经是原先被遮住的部分了
end;
以上各步是建立透明TWinControl类可视控件的必备步骤.

如果想在外界实现也是可行的(不继承), 完全可以在程序运行过程中将一个标准panel变成透明.

主要思路和上面一样, 只是需用SetWindowLong(Panel.handle, GWL_EXSTYLE, ....)
替换上述override CreateParams步骤, 然后替换panel的windowproc(需要保存原来的
windowproc地址), 用如下代码:
SetWindowLong(Panel.handle, GWL_WNDPROC, integer(@NewWindowProc));
在NewWindowProc过程中判断接受的消息是否是WM_ERASEBKGND, 如果是, 则直接返回, 否
则用CallWindowProc调用原来panel的windowproc处理)

最后RecreateWnd, 重建整个form, 你就会发觉原来不透明的panel变透明了(对其他控件没有
影响)

boatzm 2003-11-19