LazActiveX: what changed

Revision 1 to 2. Removed lines have a minus sign; added lines have a plus sign.

Old	New		Line
1	1		## Overview
2	2
3	3		The LazActiveX package contains the TActiveXContainer component and the IDE integration of the necessary tools to create ActiveX components from a type library or directly from the object (exe or dll). ActiveX is a Microsoft Windows technology and can only be used on that platform. Cross compilation to windows is possible but the typelib importer used to create the COM bindings works only on Windows (wine not tested).
4	4
5	5		## Installing
6	6
7	7		> Warning: LazActiveX needs FPC newer than 2.6.1. Importing type libraries only works on Windows XP or newer.
8	8
9	9		From the 'Package'/'Install/Uninstall Packages ...' window, select LazActiveX 0.1, click 'Install Selected' and then 'Save and Rebuild IDE'. Alternatively, open the LazActiveX.lpk package and click on 'Use \>\>'/'Install'.
10	10
11	11		When the installation succeeds, a new 'ActiveX' tab is added to your component palette.
12	12
13		-	~~<figure>~~
14		-	~~<img src="LazActiveX-Install1.png" title="LazActiveX-Install1.png" />~~
15		-	~~<figcaption>LazActiveX-Install1.png</figcaption>~~
16		-	~~</figure>~~
	13	+	![](/wiki-images/9/91/LazActiveX-Install1.png)
17	14
18	15		## Usage
19	16
20	17		There are 3 different ways of using ActiveX components:
21	18
22	19		1. drop the TActiveXContainer on a form and assign the ActiveX ClassName to the OleClassName property. Suitable for late binding and without direct event support.
23	20		2. import the ActiveX type library, drop the TActiveXContainer on a form, instantiate the ActiveX object and assign it to the ComServer property. Suitable for early binding and with event support.
24	21		3. create a new component from the type library or the object and drop that new component on the form. This also uses early binding and has full event support. Event handlers can be assigned from the IDE.
25	22
26	23		### TActiveXContainer late binding
27	24
28	25		Although the theory is quite complex, late binding is the fastest way to get an ActiveX component running.
29	26
30	27		Late binding refers to the fact that the interfacing to the object is all done at run-time. References to objects are stored as dispinterfaces in variants and the methods and properties of the objects are "discovered" at run-time.
31	28
32	29		The compiler generates all the run-time magic for you, but the downside is that the compiler isn't able to help you in finding the names of methods or properties at design time.
33	30
34	31		Good documentation for the ActiveX object is very important (sample code for VB can easily be translated to Pascal). All errors in method names and their parameters are run-time errors. The run-time "discovery" also adds quite some overhead.
35	32
36	33		Example: Embed VLC player in a form. VLC has to be installed !!
37	34
38	35		- Drop a TActiveXContainer, a TButton and a TFileNameEdit on a form.
39	36		- Resize and position TActiveXContainer to your liking and enter 'VideoLAN.VLCPlugin.2' as OleClassName, set Active to true. This will give a form that resembles the following:
40	37
41		-	~~<figure>~~
42		-	~~<img src="LazActiveX-VLC-Form.png" title="LazActiveX-VLC-Form.png" />~~
43		-	~~<figcaption>LazActiveX-VLC-Form.png</figcaption>~~
44		-	~~</figure>~~
	38	+	![](/wiki-images/3/37/LazActiveX-VLC-Form.png)
45	39
46	40		- create an Onclick event for the button and enter
47	41
48	42		``` pascal
49	43		procedure TForm1.Button1Click(Sender: TObject);
50	44		var
51	45		actx: variant;
52	46		fn: widestring;
53	47		begin
54	48		actx := ActiveXContainer1.ComServer;
55	49		fn := UTF8Decode('file:///'+StringReplace(FileNameEdit1.FileName, '\', '/', [rfReplaceAll]));
56	50		// or using uriparser (add uriparser unit to uses clause)
57	51		// fn := UTF8Decode(UriParser.FilenameToURI(FileNameEdit1.FileName));
58	52		actx.playlist.add(fn);
59	53		actx.playlist.play;
60	54		end;
61	55		```
62	56
63	57		- Run the program, select a movie and click the button to view the movie. Note that VLC and gdb seem to cause some problems (slow start-up in the best case, hangs or crashes). Run the program preferably outside the IDE.
64	58
65	59		### TActiveXContainer early binding
66	60
67	61		Early binding means that all interfaces are known to the compiler. So we need to create the pascal bindings for the ActiveX object. The importtl.exe tool in the fpc utils directory does that for you and creates coclasses and event listeners to facilitate the use of the objects in pascal. A GUI for the importtl.exe tool is integrated with the LazActiveX package and is accessible in the Tools menu: Import Type Library.
68	62
69		-	~~<figure>~~
70		-	~~<img src="LazActiveX-Importtl.png" title="LazActiveX-Importtl.png" />~~
71		-	~~<figcaption>LazActiveX-Importtl.png</figcaption>~~
72		-	~~</figure>~~
	63	+	![](/wiki-images/4/47/LazActiveX-Importtl.png)
73	64
74	65		Check 'Convert dependent typelibs' to convert also the typelibs for the COM objects that are eventually used by the selected object. Clicking OK will start the typelib import and create new units in the IDE. The units have the following naming: LibraryName_MajorVersion_MinorVersion_TLB. Ex: Access_9_0_TLB.
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76	67
77	68		Delphi users: Delphi unit naming does not use version numbers.
78	69
79	70		Instantiating an ActiveX object is done at run-time by calling the Create method for the appropriate CoClass created for the library. Some ActiveX libraries expose several objects and multiple CoClasses are created. Consult the documentation for the ActiveX library in case of doubt. Assigning the instantiated ActiveX object to the ComServer property of an TActiveXContainer on a form and setting it's active property to true is all that is needed to embed it in the application.
80	71
81	72		Example: Embed VLC player in a form. VLC has to be installed !!
82	73
83	74		\- Drop a TActiveXContainer, a TButton and a TFileNameEdit on a form. Resize and position TActiveXContainer to your liking
84	75
85	76		\- Open 'Import Type Library' from the tools menu and select 'axvlc.dll' in your VLC installation directory. Click OK. The AXVLC_1_0_TLB unit is created.
86	77
87	78		\- Add AXVLC_1_0_TLB to the uses clause.
88	79
89	80		\- Create an OnClick event for the button and an OnCreate event for the form. Enter the following code:
90	81
91	82		``` pascal
92	83		uses ..., variants, ....
93	84
94	85		var
95	86		VLC:IVLCControl2;
96	87
97	88		procedure TForm1.Button1Click(Sender: TObject);
98	89		var fn: widestring;
99	90		begin
100	91		fn := UTF8Decode('file:///'+StringReplace(FileNameEdit1.FileName, '\', '/', [rfReplaceAll]));
101	92		VLC.playlist.add(fn,'',vararrayof([':aspect-ratio=16:9']));
102	93		VLC.playlist.play;
103	94		end;
104	95
105	96		procedure TForm1.FormCreate(Sender: TObject);
106	97		begin
107	98		VLC:=CoVLCPlugin2.Create;
108	99		ActiveXContainer1.ComServer:=VLC;
109	100		ActiveXContainer1.Active:=true;
110	101		end;
111	102		```
112	103
113	104		\- Run the program, select a movie and click the button to view the movie.
114	105
115	106		The typelib importer adds also event support for ActiveX that generate them. In that case, alongside the CoClass a TEventSink descendant is defined that implements the ActiveX object and all its OnEvent properties. Use the TEventSink descendant instead of the CoClass if you want to use the events. Its name starts with TEvs followed by the class name.
116	107
117	108		Example: Internet Explorer in a form with event support.
118	109
119	110		\- Drop a TActiveXContainer, a TButton, TLabel and a TEdit on a form. Resize and position TActiveXContainer to your liking
120	111
121	112		\- Open 'Import Type Library' from the tools menu and select 'C:\WINDOWS\system32\ieframe.dll'. Click OK. The SHDocVw_1_1_TLB unit is created.
122	113
123	114		\- Add SHDocVw_1_1_TLB to the uses clause.
124	115
125	116		\- Create an OnClick event for the button and an OnCreate event for the form.
126	117
127	118		\- Create in class TForm1 the private procedure OnStatusTextChange(Sender: TObject;Text_:WideString);
128	119
129	120		\- Enter the following code:
130	121
131	122		``` pascal
132	123		var
133	124		Browser:TEvsWebBrowser;
134	125
135	126		procedure TForm1.Button1Click(Sender: TObject);
136	127		var
137	128		url,onull:Olevariant;
138	129
139	130		begin
140	131		url:=Utf8decode(Edit1.Text);
141	132		onull:=NULL;
142	133		Browser.ComServer.Navigate2(url,onull,onull,onull,onull);
143	134		end;
144	135
145	136		procedure TForm1.FormCreate(Sender: TObject);
146	137		begin
147	138		Browser:=TEvsWebBrowser.Create(Self);
148	139		ActiveXContainer1.ComServer:=Browser.ComServer;
149	140		ActiveXContainer1.Active:=true;
150	141		Browser.OnStatusTextChange:=@OnStatusTextChange;
151	142		end;
152	143
153	144		procedure TForm1.FormDestroy(Sender: TObject);
154	145		begin
155	146		Browser.Free;
156	147		end;
157	148
158	149		procedure TForm1.OnStatusTextChange(Sender: TObject; Text_: WideString);
159	150		begin
160	151		Label1.Caption:=UTF8Encode(Text_);
161	152		end;
162	153		```
163	154
164	155		\- Run the program, enter an URL in the Edit control and click the button to navigate to the URL. Label1 will show the status messages sent by the browser.
165	156
166	157		\- To access the document object (DOM) you have to import also the typelib from C:\WINDOWS\system32\mshtml.tlb and add the created MSHTML_4_0_TLB to the uses clause. To display for example the contents of the \<body\> tag of the downloaded page, add a TMemo and a second TButton to the form and add the following code:
167	158
168	159		``` pascal
169	160		procedure TForm1.Button2Click(Sender: TObject);
170	161		var Doc: IHTMLDocument2; //defined in MSHTML_4_0_TLB
171	162		begin
172	163		Doc := Browser.ComServer.Document as IHTMLDocument2;
173	164		Memo1.Lines.Text := utf8encode(Doc.parentWindow.document.Get_body.innerHTML);
174	165		end;
175	166		```
176	167
177	168		Note that CoClasses are not destroyed. As all COM objects they are reference counted and destroy themselves when the last reference goes out of scope. The TEventSink descendant has to be destroyed.
178	169
179	170		### Creating visual ActiveX components from type libraries or objects
180	171
181	172		Instead of using the TActiveXContainer component directly the importtl tool can create TActiveXContainer descendants for every ActiveX object embedded in the type library and create a lpk package for you. The descendants have full support for events generated by the objects. To create a package with the ActiveX components open the 'Import Type Library' window in the 'Tools' menu. Select the library to import, check 'Create package' and eventually 'Convert dependent typelibs', click on 'OK' to create the package. You will be prompted for a directory to store the package. Install the new package. After the Lazarus rebuild you'll find the new components in the ActiveX tab of the component palette.
182	173
183		-	~~<figure>~~
184		-	~~<img src="LazActiveX-Install2.png" title="LazActiveX-Install2.png" />~~
185		-	~~<figcaption>LazActiveX-Install2.png</figcaption>~~
186		-	~~</figure>~~
	174	+	![](/wiki-images/2/21/LazActiveX-Install2.png)
187	175
188	176		Example: Embed VLC player in a form. VLC has to be installed !!
189	177
190	178		\- Open 'Import Type Library' from the tools menu and select 'axvlc.dll' in your VLC installation directory. Check 'Create package'. Click OK. Select a directory to store the package. The AXVLC_1_0_TLBP package and all the needed units are created. Install the AXVLC_1_0_TLBP package and rebuild the IDE.
191	179
192	180		\- Drop a TAxcVLCPlugin2 (from ActiveX component tab), a TButton and a TFileNameEdit on a form.
193	181
194	182		\- Set TAxcVLCPlugin2.Active to true and resize and position TActiveXContainer to your liking.
195	183
196	184		\- Create an Onclick event for the button and enter:
197	185
198	186		``` pascal
199	187		uses variants, URIParser;
200	188		...
201	189		procedure TForm1.Button1Click(Sender: TObject);
202	190		begin
203	191		AxcVLCPlugin2_1.OleServer.playlist.add(URIParser.FilenameToURI(FileNameEdit1.FileName),'',vararrayof([':aspect-ratio=16:9']));
204	192		AxcVLCPlugin2_1.OleServer.playlist.play;
205	193		end;
206	194		```
207	195
208	196		\- Run the program, select a movie and click the button to view the movie.
209	197
210	198		Event handlers for the components can be created directly from the Object Inspector. (Note the VLC version 1.1.5.0 typelib advertises events but fails to establish a connection point. This appears to be a bug in VLC).
211	199
212	200
213	201		Delphi users: Delphi creates a stub for every method and property in its ActiveX components. importtl does not add this additional layer and the AxctiveX methods are called through the components OleServer property. Fe. AxcVLCPlugin2_1.OleServer.playlist.play is the equivalent to VLCPlugin21.playlist.play in Delphi.
214	202
215	203		---
216	204		From the Free Pascal wiki, page "LazActiveX", as it stood on 2023-04-09 after a change by Serbod, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
217	205		Category: Components
218	206		Category: Lazarus
219	207		Category: Lazarus IDE plugins

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