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Comparing ibx/trunk/runtime/IBEvents.pas (file contents):
Revision 17 by tony, Sat Dec 28 19:22:24 2013 UTC vs.
Revision 47 by tony, Mon Jan 9 15:31:51 2017 UTC

#	Line 1 | Line 1
1	<	{************************************************************************}
2	<	{                                                                        }
3	<	{       Borland Delphi Visual Component Library                          }
4	<	{       InterBase Express core components                                }
5	<	{                                                                        }
6	<	{       Copyright (c) 1998-2000 Inprise Corporation                      }
7	<	{                                                                        }
8	<	{    InterBase Express is based in part on the product                   }
9	<	{    Free IB Components, written by Gregory H. Deatz for                 }
10	<	{    Hoagland, Longo, Moran, Dunst & Doukas Company.                     }
11	<	{    Free IB Components is used under license.                           }
12	<	{                                                                        }
13	<	{    The contents of this file are subject to the InterBase              }
14	<	{    Public License Version 1.0 (the "License"); you may not             }
15	<	{    use this file except in compliance with the License. You            }
16	<	{    may obtain a copy of the License at http://www.Inprise.com/IPL.html }
17	<	{    Software distributed under the License is distributed on            }
18	<	{    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either              }
19	<	{    express or implied. See the License for the specific language       }
20	<	{    governing rights and limitations under the License.                 }
21	<	{    The Original Code was created by InterBase Software Corporation     }
22	<	{       and its successors.                                              }
23	<	{    Portions created by Inprise Corporation are Copyright (C) Inprise   }
24	<	{       Corporation. All Rights Reserved.                                }
25	<	{    Contributor(s): Jeff Overcash                                       }
26	<	{                                                                        }
27	<	{    IBX For Lazarus (Firebird Express)                                  }
28	<	{    Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
29	<	{    Portions created by MWA Software are copyright McCallum Whyman      }
30	<	{    Associates Ltd 2011                                                 }
31	<	{                                                                        }
32	<	{************************************************************************}
33	<
34	<	{
35	<	This unit has been almost completely re-written as the original code was
36	<	not that robust - and I am not even sure if it worked. The IBPP C++ implementation
37	<	was used for guidance and inspiration. A permanent thread is used to receive
38	<	events from the asynchronous event handler. This then uses "Synchronize" to
39	<	process the event in the main thread.
40	<
41	<	Note that an error will occur if the TIBEvent's Registered property is set to
42	<	true before the Database has been opened.
43	<	}
44	<
45	<	unit IBEvents;
46	<
47	<	{$Mode Delphi}
48	<
49	<	interface
50	<
51	<	uses
52	<	{$IFDEF WINDOWS }
53	<	Windows,
54	<	{$ELSE}
55	<	unix,
56	<	{$ENDIF}
57	<	Classes, Graphics, Controls,
58	<	Forms, Dialogs, IBHeader, IBExternals, IB, IBDatabase;
59	<
60	<	const
61	<	MaxEvents = 15;
62	<
63	<	type
64	<
65	<	TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
66	<	var CancelAlerts: Boolean) of object;
67	<
68	<	{ TIBEvents }
69	<
70	<	TIBEvents = class(TComponent)
71	<	private
72	<	FIBLoaded: Boolean;
73	<	FBase: TIBBase;
74	<	FEvents: TStrings;
75	<	FOnEventAlert: TEventAlert;
76	<	FEventHandler: TObject;
77	<	FRegistered: boolean;
78	<	FDeferredRegister: boolean;
79	<	procedure EventChange(sender: TObject);
80	<	function GetDatabase: TIBDatabase;
81	<	function GetDatabaseHandle: TISC_DB_HANDLE;
82	<	procedure SetDatabase( value: TIBDatabase);
83	<	procedure ValidateDatabase( Database: TIBDatabase);
84	<	procedure DoBeforeDatabaseDisconnect(Sender: TObject);
85	<	procedure DoAfterDatabaseConnect(Sender: TObject);
86	<	protected
87	<	procedure Notification( AComponent: TComponent; Operation: TOperation); override;
88	<	procedure SetEvents( value: TStrings);
89	<	procedure SetRegistered( value: boolean);
90	<
91	<	public
92	<	constructor Create( AOwner: TComponent); override;
93	<	destructor Destroy; override;
94	<	procedure RegisterEvents;
95	<	procedure UnRegisterEvents;
96	<	property DatabaseHandle: TISC_DB_HANDLE read GetDatabaseHandle;
97	<	property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
98	<	published
99	<	property Database: TIBDatabase read GetDatabase write SetDatabase;
100	<	property Events: TStrings read FEvents write SetEvents;
101	<	property Registered: Boolean read FRegistered write SetRegistered;
102	<	property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
103	<	end;
104	<
105	<
106	<	implementation
107	<
108	<	uses
109	<	IBIntf, syncobjs;
110	<
111	<	type
112	<
113	<	TEventHandlerStates = (
114	<	stIdle,           {Events not monitored}
115	<	stHasEvb,         {Event Block Allocated but not queued}
116	<	stQueued,         {Waiting for Event}
117	<	stSignalled       {Event Callback signalled Event}
118	<	);
119	<
120	<	{ TEventHandler }
121	<
122	<	TEventHandler = class(TThread)
123	<	private
124	<	FOwner: TIBEvents;
125	<	FCriticalSection: TCriticalSection;   {protects race conditions in stQueued state}
126	<	{$IFDEF WINDOWS}
127	<	{Make direct use of Windows API as TEventObject don't seem to work under
128	<	Windows!}
129	<	FEventHandler: THandle;
130	<	{$ELSE}
131	<	FEventWaiting: TEventObject;
132	<	{$ENDIF}
133	<	FState: TEventHandlerStates;
134	<	FEventBuffer: PChar;
135	<	FEventBufferLen: integer;
136	<	FEventID: ISC_LONG;
137	<	FRegisteredState: Boolean;
138	<	FResultBuffer: PChar;
139	<	FEvents: TStringList;
140	<	FSignalFired: boolean;
141	<	procedure QueueEvents;
142	<	procedure CancelEvents;
143	<	procedure HandleEventSignalled(length: short; updated: PChar);
144	<	procedure DoEventSignalled;
145	<	protected
146	<	procedure Execute; override;
147	<	public
148	<	constructor Create(Owner: TIBEvents);
149	<	destructor Destroy; override;
150	<	procedure Terminate;
151	<	procedure RegisterEvents(Events: TStrings);
152	<	procedure UnregisterEvents;
153	<	end;
154	<
155	<	{This procedure is used for the event call back - note the cdecl }
156	<
157	<	procedure IBEventCallback( ptr: pointer; length: short; updated: PChar); cdecl;
158	<	begin
159	<	if (ptr = nil) or (length = 0) or (updated = nil) then
160	<	Exit;
161	<	{ Handle events asynchronously in second thread }
162	<	TEventHandler(ptr).HandleEventSignalled(length,updated);
163	<	end;
164	<
165	<
166	<
167	<	{ TEventHandler }
168	<
169	<	procedure TEventHandler.QueueEvents;
170	<	var
171	<	callback: pointer;
172	<	DBH: TISC_DB_HANDLE;
173	<	begin
174	<	if FState <> stHasEvb then
175	<	Exit;
176	<	FCriticalSection.Enter;
177	<	try
178	<	callback := @IBEventCallback;
179	<	DBH := FOwner.DatabaseHandle;
180	<	if (isc_que_events( StatusVector, @DBH, @FEventID, FEventBufferLen,
181	<	FEventBuffer, TISC_CALLBACK(callback), PVoid(Self)) <> 0) then
182	<	IBDatabaseError;
183	<	FState := stQueued
184	<	finally
185	<	FCriticalSection.Leave
186	<	end;
187	<	end;
188	<
189	<	procedure TEventHandler.CancelEvents;
190	<	var
191	<	DBH: TISC_DB_HANDLE;
192	<	begin
193	<	if FState in [stQueued,stSignalled] then
194	<	begin
195	<	FCriticalSection.Enter;
196	<	try
197	<	DBH := FOwner.DatabaseHandle;
198	<	if (isc_Cancel_events( StatusVector, @DBH, @FEventID) <> 0) then
199	<	IBDatabaseError;
200	<	FState := stHasEvb;
201	<	finally
202	<	FCriticalSection.Leave
203	<	end;
204	<	end;
205	<
206	<	if FState = stHasEvb then
207	<	begin
208	<	isc_free( FEventBuffer);
209	<	FEventBuffer := nil;
210	<	isc_free( FResultBuffer);
211	<	FResultBuffer := nil;
212	<	FState := stIdle
213	<	end;
214	<	FSignalFired := false
215	<	end;
216	<
217	<	procedure TEventHandler.HandleEventSignalled(length: short; updated: PChar);
218	<	begin
219	<	FCriticalSection.Enter;
220	<	try
221	<	if FState <> stQueued then
222	<	Exit;
223	<	Move(Updated[0], FResultBuffer[0], Length);
224	<	FState := stSignalled;
225	<	{$IFDEF WINDOWS}
226	<	SetEVent(FEventHandler);
227	<	{$ELSE}
228	<	FEventWaiting.SetEvent;
229	<	{$ENDIF}
230	<	finally
231	<	FCriticalSection.Leave
232	<	end;
233	<	end;
234	<
235	<	procedure TEventHandler.DoEventSignalled;
236	<	var
237	<	i: integer;
238	<	CancelAlerts: boolean;
239	<	Status: array[0..19] of ISC_LONG; {Note in 64 implementation the ibase.h implementation
240	<	is different from Interbase 6.0 API documentatoin}
241	<	begin
242	<	if FState <> stSignalled then
243	<	Exit;
244	<	isc_event_counts( @Status, FEventBufferLen, FEventBuffer, FResultBuffer);
245	<	CancelAlerts := false;
246	<	if not FSignalFired then
247	<	FSignalFired := true   {Ignore first time}
248	<	else
249	<	if assigned(FOwner.FOnEventAlert)  then
250	<	begin
251	<	for i := 0 to FEvents.Count - 1 do
252	<	begin
253	<	try
254	<	if (Status[i] <> 0) and not CancelAlerts then
255	<	FOwner.FOnEventAlert( self, FEvents[i], Status[i], CancelAlerts);
256	<	except
257	<	Application.HandleException( nil);
258	<	end;
259	<	end;
260	<	end;
261	<	FState := stHasEvb;
262	<	if  CancelAlerts then
263	<	CancelEvents
264	<	else
265	<	QueueEvents
266	<	end;
267	<
268	<	procedure TEventHandler.Execute;
269	<	begin
270	<	while not Terminated do
271	<	begin
272	<	{$IFDEF WINDOWS}
273	<	WaitForSingleObject(FEventHandler,INFINITE);
274	<	{$ELSE}
275	<	FEventWaiting.WaitFor(INFINITE);
276	<	{$ENDIF}
277	<
278	<	if not Terminated and (FState = stSignalled) then
279	<	Synchronize(DoEventSignalled)
280	<	end;
281	<	end;
282	<
283	<
284	<
285	<	constructor TEventHandler.Create(Owner: TIBEvents);
286	<	var
287	<	PSa : PSecurityAttributes;
288	<	{$IFDEF WINDOWS}
289	<	Sd : TSecurityDescriptor;
290	<	Sa : TSecurityAttributes;
291	<	begin
292	<	InitializeSecurityDescriptor(@Sd,SECURITY_DESCRIPTOR_REVISION);
293	<	SetSecurityDescriptorDacl(@Sd,true,nil,false);
294	<	Sa.nLength := SizeOf(Sa);
295	<	Sa.lpSecurityDescriptor := @Sd;
296	<	Sa.bInheritHandle := true;
297	<	PSa := @Sa;
298	<	{$ELSE}
299	<	begin
300	<	PSa:= nil;
301	<	{$ENDIF}
302	<	inherited Create(true);
303	<	FOwner := Owner;
304	<	FState := stIdle;
305	<	FCriticalSection := TCriticalSection.Create;
306	<	{$IFDEF WINDOWS}
307	<	FEventHandler := CreateEvent(PSa,false,true,nil);
308	<	{$ELSE}
309	<	FEventWaiting := TEventObject.Create(PSa,false,true,FOwner.Name+'.Events');
310	<	{$ENDIF}
311	<	FEvents := TStringList.Create;
312	<	FreeOnTerminate := true;
313	<	Resume
314	<	end;
315	<
316	<	destructor TEventHandler.Destroy;
317	<	begin
318	<	if assigned(FCriticalSection) then FCriticalSection.Free;
319	<	{$IFDEF WINDOWS}
320	<	CloseHandle(FEventHandler);
321	<	{$ELSE}
322	<	if assigned(FEventWaiting) then FEventWaiting.Free;
323	<	{$ENDIF}
324	<	if assigned(FEvents) then FEvents.Free;
325	<	inherited Destroy;
326	<	end;
327	<
328	<	procedure TEventHandler.Terminate;
329	<	begin
330	<	inherited Terminate;
331	<	{$IFDEF WINDOWS}
332	<	SetEvent(FEventHandler);
333	<	{$ELSE}
334	<	FEventWaiting.SetEvent;
335	<	{$ENDIF}
336	<	CancelEvents;
337	<	end;
338	<
339	<	procedure TEventHandler.RegisterEvents(Events: TStrings);
340	<	var
341	<	i: integer;
342	<	EventNames: array of PChar;
343	<	begin
344	<	UnregisterEvents;
345	<
346	<	if Events.Count = 0 then
347	<	exit;
348	<
349	<	setlength(EventNames,MaxEvents);
350	<	try
351	<	for i := 0 to Events.Count-1 do
352	<	EventNames[i] := PChar(Events[i]);
353	<	FEvents.Assign(Events);
354	<	FEventBufferlen := isc_event_block(@FEventBuffer,@FResultBuffer,
355	<	Events.Count,
356	<	EventNames[0],EventNames[1],EventNames[2],
357	<	EventNames[3],EventNames[4],EventNames[5],
358	<	EventNames[6],EventNames[7],EventNames[8],
359	<	EventNames[9],EventNames[10],EventNames[11],
360	<	EventNames[12],EventNames[13],EventNames[14]
361	<	);
362	<	FState := stHasEvb;
363	<	FRegisteredState := true;
364	<	QueueEvents
365	<	finally
366	<	SetLength(EventNames,0)
367	<	end;
368	<	end;
369	<
370	<	procedure TEventHandler.UnregisterEvents;
371	<	begin
372	<	if FRegisteredState then
373	<	begin
374	<	CancelEvents;
375	<	FRegisteredState := false;
376	<	end;
377	<	end;
378	<
379	<	{ TIBEvents }
380	<
381	<	procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
382	<	begin
383	<	if not assigned( Database) then
384	<	IBError(ibxeDatabaseNameMissing, [nil]);
385	<	if not Database.Connected then
386	<	IBError(ibxeDatabaseClosed, [nil]);
387	<	end;
388	<
389	<	constructor TIBEvents.Create( AOwner: TComponent);
390	<	begin
391	<	inherited Create( AOwner);
392	<	FIBLoaded := False;
393	<	CheckIBLoaded;
394	<	FIBLoaded := True;
395	<	FBase := TIBBase.Create(Self);
396	<	FBase.BeforeDatabaseDisconnect := DoBeforeDatabaseDisconnect;
397	<	FBase.AfterDatabaseConnect := DoAfterDatabaseConnect;
398	<	FEvents := TStringList.Create;
399	<	with TStringList( FEvents) do
400	<	begin
401	<	OnChange := EventChange;
402	<	Duplicates := dupIgnore;
403	<	end;
404	<	FEventHandler := TEventHandler.Create(self)
405	<	end;
406	<
407	<	destructor TIBEvents.Destroy;
408	<	begin
409	<	if FIBLoaded then
410	<	begin
411	<	UnregisterEvents;
412	<	SetDatabase(nil);
413	<	TStringList(FEvents).OnChange := nil;
414	<	FBase.Free;
415	<	FEvents.Free;
416	<	end;
417	<	if assigned(FEventHandler) then
418	<	TEventHandler(FEventHandler).Terminate;
419	<	FEventHandler := nil;
420	<	inherited Destroy;
421	<	end;
422	<
423	<
424	<
425	<	procedure TIBEvents.EventChange( sender: TObject);
426	<	begin
427	<	{ check for blank event }
428	<	if TStringList(Events).IndexOf( '') <> -1 then
429	<	IBError(ibxeInvalidEvent, [nil]);
430	<	{ check for too many events }
431	<	if Events.Count > MaxEvents then
432	<	begin
433	<	TStringList(Events).OnChange := nil;
434	<	Events.Delete( MaxEvents);
435	<	TStringList(Events).OnChange := EventChange;
436	<	IBError(ibxeMaximumEvents, [nil]);
437	<	end;
438	<	if Registered then
439	<	TEventHandler(FEventHandler).RegisterEvents(Events);
440	<	end;
441	<
442	<	procedure TIBEvents.Notification( AComponent: TComponent;
443	<	Operation: TOperation);
444	<	begin
445	<	inherited Notification( AComponent, Operation);
446	<	if (Operation = opRemove) and (AComponent = FBase.Database) then
447	<	begin
448	<	UnregisterEvents;
449	<	FBase.Database := nil;
450	<	end;
451	<	end;
452	<
453	<	procedure TIBEvents.RegisterEvents;
454	<	begin
455	<	ValidateDatabase( Database);
456	<	if csDesigning in ComponentState then FRegistered := true
457	<	else
458	<	begin
459	<	if not FBase.Database.Connected then
460	<	FDeferredRegister := true
461	<	else
462	<	begin
463	<	TEventHandler(FEventHandler).RegisterEvents(Events);
464	<	FRegistered := true;
465	<	end;
466	<	end;
467	<	end;
468	<
469	<	procedure TIBEvents.SetEvents( value: TStrings);
470	<	begin
471	<	FEvents.Assign( value);
472	<	end;
473	<
474	<	procedure TIBEvents.SetDatabase( value: TIBDatabase);
475	<	begin
476	<	if value <> FBase.Database then
477	<	begin
478	<	if Registered then UnregisterEvents;
479	<	if assigned( value) and value.Connected then ValidateDatabase( value);
480	<	FBase.Database := value;
481	<	if (FBase.Database <> nil) and FBase.Database.Connected then
482	<	DoAfterDatabaseConnect(FBase.Database)
483	<	end;
484	<	end;
485	<
486	<	function TIBEvents.GetDatabase: TIBDatabase;
487	<	begin
488	<	Result := FBase.Database
489	<	end;
490	<
491	<	procedure TIBEvents.SetRegistered( value: Boolean);
492	<	begin
493	<	FDeferredRegister := false;
494	<	if not assigned(FBase) or (FBase.Database = nil) then
495	<	begin
496	<	FDeferredRegister := value;
497	<	Exit;
498	<	end;
499	<
500	<	if value then RegisterEvents else UnregisterEvents;
501	<	end;
502	<
503	<	procedure TIBEvents.UnregisterEvents;
504	<	begin
505	<	FDeferredRegister := false;
506	<	if not FRegistered then
507	<	Exit;
508	<	if csDesigning in ComponentState then
509	<	FRegistered := false
510	<	else
511	<	begin
512	<	TEventHandler(FEventHandler).UnRegisterEvents;
513	<	FRegistered := false;
514	<	end;
515	<	end;
516	<
517	<	procedure TIBEvents.DoBeforeDatabaseDisconnect(Sender: TObject);
518	<	begin
519	<	UnregisterEvents;
520	<	end;
521	<
522	<	procedure TIBEvents.DoAfterDatabaseConnect(Sender: TObject);
523	<	begin
524	<	if FDeferredRegister then
525	<	Registered := true
526	<	end;
527	<
528	<	function TIBEvents.GetDatabaseHandle: TISC_DB_HANDLE;
529	<	begin
530	<	ValidateDatabase(FBase.Database);
531	<	Result := FBase.Database.Handle;
532	<	end;
533	<
534	<
535	<	end.
1	>	{************************************************************************}
2	>	{                                                                        }
3	>	{       Borland Delphi Visual Component Library                          }
4	>	{       InterBase Express core components                                }
5	>	{                                                                        }
6	>	{       Copyright (c) 1998-2000 Inprise Corporation                      }
7	>	{                                                                        }
8	>	{    InterBase Express is based in part on the product                   }
9	>	{    Free IB Components, written by Gregory H. Deatz for                 }
10	>	{    Hoagland, Longo, Moran, Dunst & Doukas Company.                     }
11	>	{    Free IB Components is used under license.                           }
12	>	{                                                                        }
13	>	{    The contents of this file are subject to the InterBase              }
14	>	{    Public License Version 1.0 (the "License"); you may not             }
15	>	{    use this file except in compliance with the License. You            }
16	>	{    may obtain a copy of the License at http://www.Inprise.com/IPL.html }
17	>	{    Software distributed under the License is distributed on            }
18	>	{    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either              }
19	>	{    express or implied. See the License for the specific language       }
20	>	{    governing rights and limitations under the License.                 }
21	>	{    The Original Code was created by InterBase Software Corporation     }
22	>	{       and its successors.                                              }
23	>	{    Portions created by Inprise Corporation are Copyright (C) Inprise   }
24	>	{       Corporation. All Rights Reserved.                                }
25	>	{    Contributor(s): Jeff Overcash                                       }
26	>	{                                                                        }
27	>	{    IBX For Lazarus (Firebird Express)                                  }
28	>	{    Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
29	>	{    Portions created by MWA Software are copyright McCallum Whyman      }
30	>	{    Associates Ltd 2011                                                 }
31	>	{                                                                        }
32	>	{************************************************************************}
33	>
34	>	{
35	>	This unit has been almost completely re-written as the original code was
36	>	not that robust - and I am not even sure if it worked. The IBPP C++ implementation
37	>	was used for guidance and inspiration. A permanent thread is used to receive
38	>	events from the asynchronous event handler. This then uses "Synchronize" to
39	>	process the event in the main thread.
40	>
41	>	Note that an error will occur if the TIBEvent's Registered property is set to
42	>	true before the Database has been opened.
43	>	}
44	>
45	>	unit IBEvents;
46	>
47	>	{$mode objfpc}{$H+}
48	>
49	>	interface
50	>
51	>	uses
52	>	{$IFDEF WINDOWS }
53	>	Windows,
54	>	{$ELSE}
55	>	unix,
56	>	{$ENDIF}
57	>	Classes, IBExternals, IB, IBDatabase;
58	>
59	>	const
60	>	MaxEvents = 15;
61	>
62	>	type
63	>
64	>	TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
65	>	var CancelAlerts: Boolean) of object;
66	>
67	>	{ TIBEvents }
68	>
69	>	TIBEvents = class(TComponent)
70	>	private
71	>	FBase: TIBBase;
72	>	FEventIntf: IEvents;
73	>	FEvents: TStrings;
74	>	FOnEventAlert: TEventAlert;
75	>	FRegistered: boolean;
76	>	FDeferredRegister: boolean;
77	>	FStartEvent: boolean;
78	>	procedure EventHandler(Sender: IEvents);
79	>	procedure ProcessEvents;
80	>	procedure EventChange(sender: TObject);
81	>	function GetDatabase: TIBDatabase;
82	>	procedure SetDatabase( value: TIBDatabase);
83	>	procedure ValidateDatabase( Database: TIBDatabase);
84	>	procedure DoBeforeDatabaseDisconnect(Sender: TObject);
85	>	procedure DoAfterDatabaseConnect(Sender: TObject);
86	>	protected
87	>	procedure Notification( AComponent: TComponent; Operation: TOperation); override;
88	>	procedure SetEvents( value: TStrings);
89	>	procedure SetRegistered( value: boolean);
90	>
91	>	public
92	>	constructor Create( AOwner: TComponent); override;
93	>	destructor Destroy; override;
94	>	procedure RegisterEvents;
95	>	procedure UnRegisterEvents;
96	>	property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
97	>	property EventIntf: IEvents read FEventIntf;
98	>	published
99	>	property Database: TIBDatabase read GetDatabase write SetDatabase;
100	>	property Events: TStrings read FEvents write SetEvents;
101	>	property Registered: Boolean read FRegistered write SetRegistered;
102	>	property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
103	>	end;
104	>
105	>
106	>	implementation
107	>
108	>	uses SysUtils, FBMessages;
109	>
110	>	{ TIBEvents }
111	>
112	>	procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
113	>	begin
114	>	if not assigned( Database) then
115	>	IBError(ibxeDatabaseNameMissing, [nil]);
116	>	if not Database.Connected then
117	>	IBError(ibxeDatabaseClosed, [nil]);
118	>	end;
119	>
120	>	constructor TIBEvents.Create( AOwner: TComponent);
121	>	begin
122	>	inherited Create( AOwner);
123	>	FBase := TIBBase.Create(Self);
124	>	FBase.BeforeDatabaseDisconnect := @DoBeforeDatabaseDisconnect;
125	>	FBase.AfterDatabaseConnect := @DoAfterDatabaseConnect;
126	>	FEvents := TStringList.Create;
127	>	FStartEvent := true;
128	>	with TStringList( FEvents) do
129	>	begin
130	>	OnChange := @EventChange;
131	>	Duplicates := dupIgnore;
132	>	end;
133	>	end;
134	>
135	>	destructor TIBEvents.Destroy;
136	>	begin
137	>	UnregisterEvents;
138	>	SetDatabase(nil);
139	>	TStringList(FEvents).OnChange := nil;
140	>	FBase.Free;
141	>	FEvents.Free;
142	>	end;
143	>
144	>	procedure TIBEvents.EventHandler(Sender: IEvents);
145	>	begin
146	>	TThread.Synchronize(nil,@ProcessEvents);
147	>	end;
148	>
149	>	procedure TIBEvents.ProcessEvents;
150	>	var EventCounts: TEventCounts;
151	>	CancelAlerts: Boolean;
152	>	i: integer;
153	>	begin
154	>	if (csDestroying in ComponentState) or (FEventIntf = nil) then Exit;
155	>	CancelAlerts := false;
156	>	EventCounts := FEventIntf.ExtractEventCounts;
157	>	if FStartEvent then
158	>	FStartEvent := false {ignore the first one}
159	>	else
160	>	if assigned(FOnEventAlert) then
161	>	begin
162	>	CancelAlerts := false;
163	>	for i := 0 to Length(EventCounts) -1 do
164	>	begin
165	>	OnEventAlert(self,EventCounts[i].EventName,EventCounts[i].Count,CancelAlerts);
166	>	if CancelAlerts then break;
167	>	end;
168	>	end;
169	>	if CancelAlerts then
170	>	UnRegisterEvents
171	>	else
172	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
173	>	end;
174	>
175	>	procedure TIBEvents.EventChange( sender: TObject);
176	>	begin
177	>	{ check for blank event }
178	>	if TStringList(Events).IndexOf( '') <> -1 then
179	>	IBError(ibxeInvalidEvent, [nil]);
180	>	{ check for too many events }
181	>	if Events.Count > MaxEvents then
182	>	begin
183	>	TStringList(Events).OnChange := nil;
184	>	Events.Delete( MaxEvents);
185	>	TStringList(Events).OnChange := @EventChange;
186	>	IBError(ibxeMaximumEvents, [nil]);
187	>	end;
188	>	if Registered  and (FEventIntf <> nil) then
189	>	begin
190	>	FEventIntf.SetEvents(Events);
191	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
192	>	end;
193	>	end;
194	>
195	>	procedure TIBEvents.Notification( AComponent: TComponent;
196	>	Operation: TOperation);
197	>	begin
198	>	inherited Notification( AComponent, Operation);
199	>	if (Operation = opRemove) and (AComponent = FBase.Database) then
200	>	begin
201	>	UnregisterEvents;
202	>	FBase.Database := nil;
203	>	end;
204	>	end;
205	>
206	>	procedure TIBEvents.RegisterEvents;
207	>	begin
208	>	if FRegistered then Exit;
209	>	ValidateDatabase( Database);
210	>	if csDesigning in ComponentState then FRegistered := true
211	>	else
212	>	begin
213	>	if not FBase.Database.Connected then
214	>	FDeferredRegister := true
215	>	else
216	>	begin
217	>	FEventIntf := Database.Attachment.GetEventHandler(Events);
218	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
219	>	FRegistered := true;
220	>	end;
221	>	end;
222	>	end;
223	>
224	>	procedure TIBEvents.SetEvents( value: TStrings);
225	>	begin
226	>	FEvents.Assign( value);
227	>	end;
228	>
229	>	procedure TIBEvents.SetDatabase( value: TIBDatabase);
230	>	begin
231	>	if value <> FBase.Database then
232	>	begin
233	>	if Registered then UnregisterEvents;
234	>	if assigned( value) and value.Connected then ValidateDatabase( value);
235	>	FBase.Database := value;
236	>	if (FBase.Database <> nil) and FBase.Database.Connected then
237	>	DoAfterDatabaseConnect(FBase.Database)
238	>	end;
239	>	end;
240	>
241	>	function TIBEvents.GetDatabase: TIBDatabase;
242	>	begin
243	>	Result := FBase.Database
244	>	end;
245	>
246	>	procedure TIBEvents.SetRegistered(value: boolean);
247	>	begin
248	>	FDeferredRegister := false;
249	>	if not assigned(FBase) or (FBase.Database = nil) then
250	>	begin
251	>	FDeferredRegister := value;
252	>	Exit;
253	>	end;
254	>
255	>	if value then RegisterEvents else UnregisterEvents;
256	>	end;
257	>
258	>	procedure TIBEvents.UnRegisterEvents;
259	>	begin
260	>	FDeferredRegister := false;
261	>	if not FRegistered then
262	>	Exit;
263	>	if csDesigning in ComponentState then
264	>	FRegistered := false
265	>	else
266	>	begin
267	>	FEventIntf := nil;
268	>	FRegistered := false;
269	>	end;
270	>	end;
271	>
272	>	procedure TIBEvents.DoBeforeDatabaseDisconnect(Sender: TObject);
273	>	begin
274	>	UnregisterEvents;
275	>	end;
276	>
277	>	procedure TIBEvents.DoAfterDatabaseConnect(Sender: TObject);
278	>	begin
279	>	if FDeferredRegister then
280	>	Registered := true
281	>	end;
282	>
283	>
284	>	end.

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