一个使TEdit透明的例子

最新推荐文章于 2017-10-25 10:39:01 发布

原创最新推荐文章于 2017-10-25 10:39:01 发布 · 1.5k 阅读

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CC 4.0 BY-SA版权

文章标签：

#constructor #forms #interface #windows #class #user

该博客主要围绕TBKTransparentEdit类展开，涉及该类的接口定义、构造函数、窗口创建、消息处理等方法的实现。通过对不同消息的处理，实现了透明编辑框的功能，如处理背景擦除、移动等消息，还包含注册组件的过程。

unit BKTransparentEdit;

interface

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

const
TWM_BKInvalidate=WM_USER+1;

type
TBKTransparentEdit = class(TEdit)
private
    { Private declarations }
    procedure BKInvalidate(var Message:TMessage); message
              TWM_BKInvalidate;
    procedure CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT); message
              CN_CTLCOLOREDIT;
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
    procedure WMMove(var Message: TMessage); message WM_MOVE;

protected
    { Protected declarations }
    FTransparent: boolean;
    procedure CreateWnd; override;
    procedure CreateParams(var Params: TCreateParams); override;
    procedure DoExit; override;
    procedure DoEnter; override;
public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    procedure Invalidate; override;

published
{ Published declarations }
end;

procedure Register;

implementation

constructor TBKTransparentEdit.Create(AOwner:TComponent);
begin
inherited Create(AOwner);
FTransparent:=true;
end;

procedure TBKTransparentEdit.CreateWnd;
begin
inherited CreateWnd;
if FTransparent then begin
SetWindowLong(Parent.Handle, GWL_STYLE,GetWindowLong(Parent.Handle, GWL_STYLE) and not WS_CLIPCHILDREN);
end;
end;

procedure TBKTransparentEdit.BKInvalidate(var Message:TMessage);
var
r:TRect;
begin
if (Parent<>nil) and FTransparent then begin
    r:=ClientRect;
    r.TopLeft:=Parent.ScreenToClient(ClientToScreen(r.TopLeft));
    r.BottomRight:=Parent.ScreenToClient(ClientToScreen(r.BottomRight));
    RedrawWindow(Handle,nil,0,RDW_FRAME+RDW_INVALIDATE);
end;
end;

procedure TBKTransparentEdit.CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT);
begin
if FTransparent then
with Message do
begin
    SetBkMode(ChildDC,Windows.TRANSPARENT);
    Result:=GetStockObject(HOLLOW_BRUSH)
end
else
    inherited;
end;

procedure TBKTransparentEdit.WMEraseBkgnd(var Message:TWMERASEBKGND);
begin
if FTransparent and not (csDesigning in ComponentState) then
PostMessage(Handle,TWM_BKInvalidate,0,0)
else
inherited;
end;

procedure TBKTransparentEdit.WMMove(var message:TMessage);
begin
inherited;
if FTransparent then
SendMessage(Handle,TWM_BKInvalidate,0,0)
else
Invalidate;
end;

procedure TBKTransparentEdit.CreateParams(var Params:TCreateParams);
begin
inherited CreateParams(Params);
if (CsDesigning in ComponentState) then exit;
with Params do
begin
ExStyle:=ExStyle or WS_EX_TRANSPARENT;
end;
end;

procedure TBKTransparentEdit.DoExit;
begin
inherited;
   FTransparent:=true;
   SetCursor(0);
   RecreateWnd;
end;

procedure TBKTransparentEdit.DoEnter;
var
exstyle,stdstyle:longint;
begin
inherited;
FTransparent:=false;
StdStyle:= Windows.GetWindowLong(handle, GWL_EXSTYLE);
exStyle:= StdStyle and not WS_EX_TRANSPARENT;
Windows.SetWindowLong(handle, GWL_EXSTYLE, exStyle);
invalidate;
end;

procedure TBKTransparentEdit.Invalidate;
begin
if FTransparent then
SendMessage(Handle,TWM_BKInvalidate,0,0)
else
inherited;
end;

procedure Register;
begin
RegisterComponents('BKTransparentComps', [TBKTransparentEdit]);
end;

end.