fcl-registry: what changed

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Title: fcl-registry

New		Line
1	+	fcl-registry is an [[FCL]] unit that provides access to the Windows registry. It is cross-platform. How? In non-Windows operating systems it creates a `reg.xml` file. For example, under non-Windows operating systems it creates the per user XML file (HKEY_CURRENT_USER) `reg.xml` in the `/home/[user]/.config/application_name/` directory; the global XML file (HKEY_LOCAL_MACHINE) `reg.xml` is created in the `/etc/application_name/` directory which is invariably a read-only location unless you are the root or Admin user.
2	+
3	+	## Registry terms
4	+
5	+	RootKey: registry hive where you want to start accessing the registry. Examples: HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER
6	+
7	+	Key: the path to the "directory" that contains individual data. This is a bit counter-intuitive but a holdover from compatibility with earlier versions of the registry.
8	+
9	+	Name/value: the actual name/value pairs in the Key "directory". Each key can have a default value, whose name is (an empty string).
10	+
11	+	## Example
12	+
13	+	Example that tries to get a value:
14	+
15	+	``` pascal
16	+	uses ... registry...
17	+
18	+	var
19	+	CompileCommand: string='';
20	+	Registry: TRegistry;
21	+	begin
22	+	Registry := TRegistry.Create;
23	+	try
24	+	// Navigate to proper "directory":
25	+	Registry.RootKey := HKEY_LOCAL_MACHINE;
26	+	if Registry.OpenKeyReadOnly('\SOFTWARE\Classes\InnoSetupScriptFile\shell\Compile\Command') then
27	+	CompileCommand:=Registry.ReadString(''); //read the value of the default name
28	+	finally
29	+	Registry.Free; // In non-Windows operating systems this flushes the reg.xml file to disk
30	+	end;
31	+	end;
32	+	```
33	+
34	+	## Accessing 64 bit and 32 bit registry views
35	+
36	+	If you have 64 bit Windows, the registry is split up into a 64 bit and 32 bit (compatibility) part. By default, if you run a 32 bit process, you see the 32 bit part; if you run a 64 bit application, you see the 64 bit part.
37	+
38	+	You can also access the 32 bit part from 64 bit applications and vice versa. From [MSDN](http://msdn.microsoft.com/en-us/library/windows/desktop/aa384129%28v=vs.85%29.aspx)
39	+
40	+	- KEY_WOW64_64KEY: Access a 64-bit key from either a 32-bit or 64-bit application.
41	+	- KEY_WOW64_32KEY: Access a 32-bit key from either a 32-bit or 64-bit application.
42	+
43	+	These keys are defined in the registry unit so you can just use them: eg in the registry object's Access property, like this:
44	+
45	+	``` pascal
46	+	Registry := TRegistry.Create;
47	+	Try
48	+	Registry.Access:=Registry.Access or KEY_WOW64_64KEY;
49	+	```
50	+
51	+	or in the registry.create call, eg:
52	+
53	+	``` pascal
54	+	TRegistry.Create(KEY_READ or KEY_WOW64_64KEY);
55	+	```
56	+
57	+	## Administrative privileges
58	+
59	+	Depending on what you want to read/write in the Windows registry, you may need administrator rights and elevation (Windows Vista+). Please see [[IDE Window: Project Options\|Use manifest file to set execution level]]
60	+
61	+	## See also
62	+
63	+	[[Package List\|Packages List]]
64	+
65	+	---
66	+	From the Free Pascal wiki, page "fcl-registry", as it stood on 2020-05-06 after a change by Trev, 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).

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