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//------------------------------------------------------------------------------
//This Source Code Form is subject to the terms of the Mozilla Public
//License, v. 2.0. If a copy of the MPL was not distributed with this
//file, You can obtain one at http://mozilla.org/MPL/2.0/.
//------------------------------------------------------------------------------
unit BaseComp;
{$MODE Delphi}
interface
uses
LCLIntf, LCLType, LMessages, Messages, SysUtils, Classes, Controls, Forms;
type
{this component adds a window handle to the standard TControl
in order to receive windows messages and makes sure that
DoSetEnabled is called only at run time}
TBaseComponent = class (TComponent)
private
FHandle: THandle;
FEnabled : boolean;
procedure SetEnabled(AEnabled: boolean);
procedure WndProc(var Message: TMessage);
//procedure WMQueryEndSession(var Message: TMessage); message WM_QUERYENDSESSION;
protected
procedure DoSetEnabled(AEnabled: boolean); virtual;
procedure Loaded; override;
property Handle: THandle read FHandle;
public
property Enabled: boolean read FEnabled write SetEnabled default false;
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
end;
implementation
{ TBaseComponent }
constructor TBaseComponent.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FHandle := 0;
FEnabled := false;
end;
destructor TBaseComponent.Destroy;
begin
Enabled := false;
inherited Destroy;
end;
procedure TBaseComponent.Loaded;
begin
inherited Loaded;
if FEnabled then
begin
FEnabled := false;
SetEnabled(true);
end;
end;
procedure TBaseComponent.WndProc(var Message: TMessage);
begin
try
Dispatch(Message);
except
Application.HandleException(Self);
end;
end;
//procedure TBaseComponent.WMQueryEndSession(var Message: TMessage);
//begin
// try Enabled := false; except; end;
// inherited;
// Message.Result := integer(true);
//end;
procedure TBaseComponent.SetEnabled (AEnabled: boolean);
begin
if (not (csDesigning in ComponentState)) and
(not (csLoading in ComponentState)) and
(AEnabled <> FEnabled)
then DoSetEnabled(AEnabled);
FEnabled := AEnabled;
end;
procedure TBaseComponent.DoSetEnabled (AEnabled: boolean);
begin
if AEnabled
then
FHandle := AllocateHwnd(WndProc)
else
begin
if FHandle <> 0 then DeallocateHwnd(FHandle);
FHandle := 0;
end;
end;
end.
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