1. Globalization Services: Spell Checking API

2. Spell Checking API
The Spell Checking API permits developers to consume spell checker capability to check text, get suggestions, and maintain settings and user dictionaries. Developers can also create spell checkers that are integrated into the spell checking framework as providers.

3. Versioning
The Spell Checking API is available beginning with the Windows 8 or Windows Server 2012. Future additions to the API will be handled by creating new interfaces that can be determined using Queryinterface on the existing ones.

4. Interfaces The Spell Checking API contains the following interfaces:
IComprehensiveSpellCheckProvider
IEnumSpellingError
IOptionDescription
ISpellChecker
ISpellChecker2
ISpellCheckerChangedEventHandler
ISpellCheckerFactory
ISpellCheckProvider
ISpellCheckProviderFactory
ISpellingError
IUserDictionariesRegistrar

5. ISpellingError Interface
This inferface provides information about a spelling error. ISpellingError
Interface has these methods.
Method
Description
ISpellingError::get_CorrectiveAction
Indicates which corrective action should be taken for the spelling error.
ISpellingError::get_Length
Gets the length of the erroneous text.
ISpellingError::get_Replacement
Gets the text to use as replacement text when the corrective action is replace.
ISpellingError::get_StartIndex
Gets the position in the checked text where the error begins.

6. Error handling
Errors are returned as HRESULTs. Standard RPC error codes may be returned by any of the API calls because they are out-of-proc. Standard RPC timeouts apply.

7. ISpellCheckerFactory interface
ISpellCheckerFactory is the starting point for clients of the Spell Checking API, which should be created as an in-proc COM Server as shown in the example below.
SpellCheckerFactory interface has these methods.
Method
Description
ISpellCheckerFactory::CreateSpellChecker
Creates a spell checker that supports the specified language.
ISpellCheckerFactory::get_SupportedLanguages
Gets the set of languages/dialects supported by any of the registered spell checkers.
ISpellCheckerFactory::IsSupported
Determines if the specified language is supported by a registered spell checker.

8. Dictionary files
The plaintext that must start with the appropriate Byte Order Mark (BOM). Each line contains a word (in the Added and Exuser-specific dictionaries for a language, which hold the content for the Added, Excluded, and AutoCorrect word lists, are located under %AppData%\Microsoft\Spelling\. The filenames are default.dic (Added), default.exc (Excluded) and default.acl (AutoCorrect).
Other .dic, .exc, and .acl files present in the directory will be detected by the spell checking service and added to the user word lists. These files are considered to be read-only and are not modified by the spell checking API.

9. Installing a spell checking provider
The installation of a spell checking provider must place all the files it uses in a location that allows read access from the SID (security identifier) "ALL APPLICATION PACKAGES". Installing it in a folder under "Program Files" works well. Also, the provider must set some keys in the registry for it to appear to the spell checking API. It can be in either the HKEY_CURRENT_USER hive or the HKEY_LOCAL_MACHINE hive depending on whether it should install only for the current user or all users.

10. These are few provider keys:
Key: <Registry hive>\SOFTWARE\Classes\CLSID\<Server CLSID>
Default (REG_SZ) = <Name of the provider>
Key: <Registry hive>\SOFTWARE\Classes\CLSID\<Server CLSID>\InprocServer32
ThreadingModel (REG_SZ) = "Both"
Key: <Registry hive>\SOFTWARE\Classes\CLSID\<Server CLSID>\Version
Version (REG_SZ) = <Version>
Key: <Registry hive>\SOFTWARE\Microsoft\Spelling\Spellers\<Provider id string>
CLSID (REG_SZ) = <CLSID of the COM Server that implements the provider>
The spell checking provider sample provides an example of the registration needed to install a provider.
If you are creating new spell checking options for a spell checking provider, see IOptionDescription::Id for guidance on naming.

11. Sources

12. Thank you for your attention