Mega Code Archive
Building a Transparent Edit Control
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Title: Building a Transparent Edit Control
Question: How can I build a transparent edit control?
Answer:
Building a transparent edit control can be the cool face of your application. Why? Because your entry forms can look like "paper forms". Adding this cool features for your application can be very easy, as you will see bellow.
First of all I want to specify that is not my original code. I have found a transparent edit, listbox, checkbox and memo controls in FusedControls, but the main goal of this library is the flicker. Is impossible for anyone to distribute a applicatin with this controls because the flicker is in supportable.
An now, go to work. All we have to do is to overrwide the CreateParams and some common events. In order to resolve the flicker I have decide to let our edit control transparent only when the focus is not on it. So, I have override the DoEnter and DoExit. The entire code is bellow. Just copy, paste in a blank unit and install the component.
unit RbsWiredEdit;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
const
TWM_RbsInvalidate=WM_USER+1;
type
TRbsWiredEdit = class(TEdit)
private
{ Private declarations }
procedure RbsInvalidate(var Message:TMessage); message
TWM_RbsInvalidate;
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 TRbsWiredEdit.Create(AOwner:TComponent);
begin
inherited create(AOwner);
ftransparent:=true;
end;
procedure TRbsWiredEdit.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 TRbsWiredEdit.RbsInvalidate(var Message:TMessage);
var r:TRect;
begin
if (Parentnil) 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 TRbsWiredEdit.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 TRbsWiredEdit.WMEraseBkgnd(var Message:TWMERASEBKGND);
begin
if FTransparent and not (csDesigning in ComponentState) then
PostMessage(Handle,TWM_RbsInvalidate,0,0)
else inherited;
end;
procedure TRbsWiredEdit.WMMove(var message:TMessage);
begin
inherited;
if FTransparent then SendMessage(Handle,TWM_RbsInvalidate,0,0)
else Invalidate;
end;
procedure TRbsWiredEdit.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 TRbsWiredEdit.DoExit;
begin
inherited;
FTransparent:=true;
SetCursor(0);
RecreateWnd;
end;
procedure TRbsWiredEdit.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 TRbsWiredEdit.Invalidate;
begin
if FTransparent then SendMessage(Handle,TWM_RbsInvalidate,0,0)
else inherited;
end;
procedure Register;
begin
RegisterComponents('Rombest', [TRbsWiredEdit]);
end;
end.
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