A Spell Checking Engine

Description:

This project is an evolution of the spell checking engine project I submitted earlier. This project includes numerous enhancements to the core spelling engine plus the addition of a "check-as-you-type" edit control and the related support dialogs (see above).

This project is not complete, it is a work-in-progress. There are numerous issues with the current version which need to be addressed. My long term goal is to develop this to "commercial quality".

I am going to continue to improve this engine toward my goal. I will continue to post updates as I feel necessary.

Changes from previous version:

1. Reorganized class architecture. Added CFPSSpellCheckEngineOptions, CFPSDictionary to core engine.
2. Created CFPSSpellingEditCtrl CEdit derived class to implement "check-as-you-type" edit control.
3. Created options property pages (see above)
4. Created spelling dialog (see above)
5. Created common-use dictionary. (Download available above)
6. Updated US English dictionary w/improved word list + proper names.
7. Incremental changes to the MetaphoneEx function.
8. Addition of the EditDistance function.
9. Added support for case-sensitive dictionary entries.
10. Added file header to dictionaries.

To-do-list:

1. Re-write EditDistance algorithm for performance.
2. Research compression options for dictionaries
3. Create ATL ActiveX control from edit control
4. Create COM based dictionary support for language independence
5. Create Rich Edit "check-as-you-type" control.
6. Add auto-correct capability.
7. Add sentence begin recognition for automatic upper case decisions.
8. Continue to improve US English dictionary.
9. Implement a binary-search mechanism on dictionary look-ups.
10. Continue to improve MetaphoneEx function.
11. Create C# (.net) version (when C# stabilizes)
12. ETC...

Classes:

Support functions of importance:

CDlgSpellChecker

CDlgSpellChecker

void MetaphoneEx(const char *szInput, char *szOutput, int
        iMaxLen)

<a href="http://www.cuj.com/archive/1806/feature.html">Lawrence
        Philips.</a> 

Architecture:

CORE ENGINE

The core spell checking engine consists of the three classes: CFPSSpellCheckEngine,

CFPSSpellCheckEngineOptions

and CFPSDictionary. These classes provide support for dictionary related functions such as add a word, remove a word, ignore a word, load dictionary, save dictionary, Is a word in the dictionary, suggest possible matches, etc.

The core engine is implemented as a strict back-end engine. It has no user-interface components. Most of the functions exposed by these classes where an error might occur return an int return code. These return codes are defined in 1) FPSSpellCheckerInclude.h and 2) the header file for a given class. The return codes should always be examined to determine the completion status of these functions.

Special care has been taken to insure that these classes are very stable and robust. Also, performance considerations weigh heavy on the implementation of these classes. Very little MFC code is used in these classes and functions.

CHECK-AS-YOU-TYPE EDIT CONTROL

The check-as-you-type edit control is contained in the CFPSSpellingEditCtrl class. It is derived off of CEdit and works by subclassing an existing edit control through the AttachEdit function.

To improve performance, this control implements a timer and whenever there is no user activity (typing, mouse clicking, scrolling, etc) checks the spelling of the displayed portion of the edit control. The function RedrawSpellingErrors is called to perform the checking. It checks only the displayed portion of the edit control and calls DrawSpellingError for each displayed word. If a word is not found in the dictionary, this function calls DrawSquiglyI to draw the squigly underline for the word. DrawSquigly creates a structure of type FPSSPELLEDIT_ERRORS and adds it to the m_SpellingErrors member list.

The OnRButtonDown function checks the m_SpellingErrors to determine when to display the normal popup menu and when to display the spell check popup menu. Suggestions returned from the core engine are sorted using the SortMatches function to display them in order of edit-distance.

The PreTranslateMessage checks for a hot key (defaults to F7). This can be customized by calling the SetHotKey static member function. When the hot key is pressed the CheckSpellingEdit function is called to display the spell checking dialog box.

SPELL CHECK DIALOG BOX

The spell checking dialog box is implemented in the CDlgSpellChecker class. This is a standard CDialog derived class based on the IDD_SPELL_CHECK dialog resource.

The spell checking dialog is modelled after the Microsoft Word implementation of spell checking. It is laid out the same and functions (for the most part) the same. This dialog searches an edit control (or rich edit control) for sentences misspelled words and displays the sentence with the misspelled word highlighted.

Suggestions returned from the core engine are sorted using the SortMatches function to display them in order of edit-distance.

How to use the demo:

1. Unzip the provided file into a directory (be sure to extract the sub directories.)
2. Make sure that the USMain.dic file is in the \Release directory.
3. Make sure that the USCommon.dic file is in the \Release directory.
4. Execute the FPSSpellChecker.exe from the \Release directory.

How to incorporate the spell checker into an application:

1. In your applications InitInstance function, add a call to CFPSSpellingEditCtrl::InitSpellingEngine(NULL) static member function; OR, instead of NULL, pass in a string containing a fully qualified path to a spell checking engine options file.
2. In your applications ExitInstance function, add a call to CFPSSpellingEditCtrl::Terminate static member function
3. Add the following files to your project.

   DlgSpellChecker.cpp	DlgSpellChecker.h
   DlgSpellingEditCtrl.cpp	DlgSpellingEditCtrl.h
   FPSDictionary.cpp	FPSDictionary.h
   FPSSpellCheckEngine.cpp	FPSSpellCheckEngine.h
   FPSSpellCheckEngineOptions.cpp	FPSSpellCheckEngineOptions.h
   FPSSpellCheckerInclude.cpp	FPSSpellCheckerInclude.h
   FPSSpellingEditCtrl.cpp	FPSSpellingEditCtrl.h
   PrPgeSpellOptions_Common.cpp	PrPgeSpellOptions_Common.h
   PrPgeSpellOptions_General.cpp	PrPgeSpellOptions_General.h
   PrPgeSpellOptions_User.cpp	PrPgeSpellOptions_User.h
   PrShtSpellOptions.cpp	PrShtSpellOptions.h

4. Copy the following resource items to your project.

   IDD_SPELL_CHECK
   IDD_SPELL_OPTION_COMMON
   IDD_SPELL_OPTION_GENERAL
   IDD_SPELL_OPTION_USER

5. Include the "FPSSpellCheckerInclude.h" file in your stdafx.h file.

   #include "FPSSpellCheckerInclude.h"

6. Place a standard edit control on a form or dialog resource and give it a unique control id (ie. ID_TEST_EDIT)
7. Add a member variable of type CFPSSpellingEditCtrl to the dialog/form class file (ie. m_editTest)
8. In the OnInitDialog function, call the

   AttachEdit
   

   member function of CFPSSpellingEditCtrl (ie.

   m_editTest.AttachEdit(this,
       ID_TEST_EDIT);

Known Issues

1. Performance is still not as good as it needs to be.
2. Language support is limited to US English.
3. The EditDistance function needs work.
4. The MetaphoneEx function needs work.
5. There is a painting problem with the edit control when scrolling the control while the spelling error "squigly" lines are displayed.
6. No complete support for rich edit control.