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{************************************************************************}
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{ }
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{ Borland Delphi Visual Component Library }
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{ InterBase Express core components }
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{ }
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{ Copyright (c) 1998-2000 Inprise Corporation }
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{ }
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{ InterBase Express is based in part on the product }
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{ Free IB Components, written by Gregory H. Deatz for }
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{ Hoagland, Longo, Moran, Dunst & Doukas Company. }
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{ Free IB Components is used under license. }
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{ }
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{ The contents of this file are subject to the InterBase }
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{ Public License Version 1.0 (the "License"); you may not }
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{ use this file except in compliance with the License. You }
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{ may obtain a copy of the License at http://www.Inprise.com/IPL.html }
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{ Software distributed under the License is distributed on }
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{ an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either }
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{ express or implied. See the License for the specific language }
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{ governing rights and limitations under the License. }
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{ The Original Code was created by InterBase Software Corporation }
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{ and its successors. }
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{ Portions created by Inprise Corporation are Copyright (C) Inprise }
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{ Corporation. All Rights Reserved. }
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{ Contributor(s): Jeff Overcash }
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{ }
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{ IBX For Lazarus (Firebird Express) }
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{ Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
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{ Portions created by MWA Software are copyright McCallum Whyman }
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{ Associates Ltd 2011 - 2018 }
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{ }
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{************************************************************************}
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{
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This unit has been almost completely re-written as the original code was
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not that robust - and I am not even sure if it worked. The IBPP C++ implementation
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was used for guidance and inspiration. A permanent thread is used to receive
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events from the asynchronous event handler. This then uses "Synchronize" to
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process the event in the main thread.
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Note that an error will occur if the TIBEvent's Registered property is set to
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true before the Database has been opened.
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}
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unit IBEvents;
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{$mode objfpc}{$H+}
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interface
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uses
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{$IFDEF WINDOWS }
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Windows,
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{$ELSE}
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unix,
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{$ENDIF}
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Classes, IB, IBDatabase;
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const
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MaxEvents = 15;
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type
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TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
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var CancelAlerts: Boolean) of object;
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{ TIBEvents }
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TIBEvents = class(TComponent)
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private
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FBase: TIBBase;
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FEventIntf: IEvents;
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FEvents: TStrings;
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FOnEventAlert: TEventAlert;
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FRegistered: boolean;
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FDeferredRegister: boolean;
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FStartEvent: boolean;
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procedure EventHandler(Sender: IEvents);
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procedure ProcessEvents;
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procedure EventChange(sender: TObject);
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function GetDatabase: TIBDatabase;
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procedure SetDatabase( value: TIBDatabase);
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procedure ValidateDatabase( Database: TIBDatabase);
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procedure DoBeforeDatabaseDisconnect(Sender: TObject);
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procedure DoAfterDatabaseConnect(Sender: TObject);
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protected
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procedure Notification( AComponent: TComponent; Operation: TOperation); override;
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procedure SetEvents( value: TStrings);
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procedure SetRegistered( value: boolean);
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public
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constructor Create( AOwner: TComponent); override;
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destructor Destroy; override;
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procedure RegisterEvents;
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procedure UnRegisterEvents;
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property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
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property EventIntf: IEvents read FEventIntf;
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published
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property Database: TIBDatabase read GetDatabase write SetDatabase;
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property Events: TStrings read FEvents write SetEvents;
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property Registered: Boolean read FRegistered write SetRegistered;
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property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
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end;
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implementation
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uses SysUtils, FBMessages;
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{ TIBEvents }
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procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
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begin
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if not assigned( Database) then
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IBError(ibxeDatabaseNameMissing, [nil]);
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if not Database.Connected then
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IBError(ibxeDatabaseClosed, [nil]);
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end;
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constructor TIBEvents.Create( AOwner: TComponent);
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begin
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inherited Create( AOwner);
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FBase := TIBBase.Create(Self);
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FBase.BeforeDatabaseDisconnect := @DoBeforeDatabaseDisconnect;
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FBase.AfterDatabaseConnect := @DoAfterDatabaseConnect;
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FEvents := TStringList.Create;
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FStartEvent := true;
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with TStringList( FEvents) do
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begin
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OnChange := @EventChange;
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Duplicates := dupIgnore;
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end;
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end;
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destructor TIBEvents.Destroy;
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begin
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UnregisterEvents;
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SetDatabase(nil);
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TStringList(FEvents).OnChange := nil;
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FBase.Free;
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FEvents.Free;
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inherited Destroy;
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end;
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procedure TIBEvents.EventHandler(Sender: IEvents);
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begin
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TThread.Synchronize(nil,@ProcessEvents);
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end;
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procedure TIBEvents.ProcessEvents;
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var EventCounts: TEventCounts;
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CancelAlerts: Boolean;
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i: integer;
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begin
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if (csDestroying in ComponentState) or (FEventIntf = nil) then Exit;
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CancelAlerts := false;
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EventCounts := FEventIntf.ExtractEventCounts;
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if FStartEvent then
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FStartEvent := false {ignore the first one}
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else
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if assigned(FOnEventAlert) then
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begin
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CancelAlerts := false;
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for i := 0 to Length(EventCounts) -1 do
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begin
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OnEventAlert(self,EventCounts[i].EventName,EventCounts[i].Count,CancelAlerts);
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if CancelAlerts then break;
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end;
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end;
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if CancelAlerts then
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UnRegisterEvents
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else
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FEventIntf.AsyncWaitForEvent(@EventHandler);
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end;
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procedure TIBEvents.EventChange( sender: TObject);
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begin
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{ check for blank event }
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if TStringList(Events).IndexOf( '') <> -1 then
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IBError(ibxeInvalidEvent, [nil]);
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{ check for too many events }
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if Events.Count > MaxEvents then
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begin
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TStringList(Events).OnChange := nil;
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Events.Delete( MaxEvents);
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TStringList(Events).OnChange := @EventChange;
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IBError(ibxeMaximumEvents, [nil]);
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end;
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if Registered and (FEventIntf <> nil) then
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begin
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FEventIntf.SetEvents(Events);
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FEventIntf.AsyncWaitForEvent(@EventHandler);
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end;
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end;
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procedure TIBEvents.Notification( AComponent: TComponent;
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Operation: TOperation);
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begin
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inherited Notification( AComponent, Operation);
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if (Operation = opRemove) and (AComponent = FBase.Database) then
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begin
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UnregisterEvents;
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FBase.Database := nil;
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end;
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end;
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procedure TIBEvents.RegisterEvents;
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begin
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if FRegistered then Exit;
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ValidateDatabase( Database);
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if csDesigning in ComponentState then FRegistered := true
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else
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begin
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if not FBase.Database.Connected then
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FDeferredRegister := true
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else
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begin
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FEventIntf := Database.Attachment.GetEventHandler(Events);
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FEventIntf.AsyncWaitForEvent(@EventHandler);
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FRegistered := true;
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end;
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end;
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end;
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procedure TIBEvents.SetEvents( value: TStrings);
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begin
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FEvents.Assign( value);
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end;
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procedure TIBEvents.SetDatabase( value: TIBDatabase);
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begin
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if value <> FBase.Database then
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begin
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if Registered then UnregisterEvents;
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if assigned( value) and value.Connected then ValidateDatabase( value);
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FBase.Database := value;
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if (FBase.Database <> nil) and FBase.Database.Connected then
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DoAfterDatabaseConnect(FBase.Database)
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end;
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end;
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function TIBEvents.GetDatabase: TIBDatabase;
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begin
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Result := FBase.Database
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end;
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procedure TIBEvents.SetRegistered(value: boolean);
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begin
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FDeferredRegister := false;
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if not assigned(FBase) or (FBase.Database = nil) then
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begin
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FDeferredRegister := value;
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Exit;
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end;
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if value then RegisterEvents else UnregisterEvents;
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end;
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procedure TIBEvents.UnRegisterEvents;
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begin
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FDeferredRegister := false;
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if not FRegistered then
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Exit;
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if csDesigning in ComponentState then
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FRegistered := false
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else
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begin
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FEventIntf := nil;
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FRegistered := false;
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end;
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end;
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procedure TIBEvents.DoBeforeDatabaseDisconnect(Sender: TObject);
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begin
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UnregisterEvents;
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end;
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procedure TIBEvents.DoAfterDatabaseConnect(Sender: TObject);
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begin
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if FDeferredRegister then
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Registered := true
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end;
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end.
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