Autocomplection in RichEdit Control

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CAutocomplectionCtrl is a control designed to add the auto completion feature in a CRichEditCtrl. You can easily modify the code to add the auto completion feature in a CRichEditView.

You can specify options such as displaying all known words or only the matching ones.

User can start the auto completion feature pressing Ctrl+space; he can confirm the selected word pressing space, Enter or a non-alpha char; he can use up, down, pgUp, pgDown, home, end, Ctrl+Space or mouse-wheel to switch between the words in the list; he can use left, right to modify the matching part of the word.

Using the control

Using ClassWizard add a variable in your dialog class; the variable must be a CAutocomplectionCtrl control; if the ClassWizard displays only CRichEdit select it, and change it to CAutocomplectionCtrl in the .h file.

Remember to include "Autocomplection.h" in your .h file and to insert the line

AfxInitRichEdit();

in the Initinstance() function of your application.

Then you must define your dictionary using the AddKeyword() funcion; usually you'll do that in the OnInitDialog function. In the sample application I read the words from a file, so resulting code is:

while (file.ReadString(keyword))
	m_edit.AddKeyword(keyword);

Well, your work is done :)

If you like you can specify some options...

Option functions

void Enable(BOOL);

You can enable or disable the auto completion feature; by default it's enabled.

void ShowListBox(BOOL);

You can select if to display the listbox or not

void ListAllWords(BOOL);

You can select if to display in the listbox all known words, or only the matching ones

void TrapEnter(BOOL);

Pressing Enter, the selected word is confirmed.

If TrapEnter is set to FALSE, when pressing Enter, the control will add a new line char, if TrapEnter is set to TRUE, the new line char will not be displayed

void CaseSensitive(BOOL);

You can select if the matching function must be case sensitive or not.

void AutoLearn(BOOL);

That feature isn't very useful; if enabled, when the user types an unknown word, the control will add it to the dictionary; that could be nice if the user never mistakes typing words...

void LearnOnDblClick(BOOL);

If this feature is enabled, when the user double-clicks over a word, the control learns it.

Dictionary functions

void GetDictionary(CStringArray& dictionary);

This function fills the given CStringArray with all known words.

void ResetDictionary();

This function empties the dictionary.

BOOL AddKeyword(const CString& str);

This function adds the specified word in the dictionary.

BOOL IsKeyword(const CString& str);

This function checks if the specified word is in the dictionary.

Developing notes

The code compiles cleanly under the warning level 4.

Search

I chose to insert word in alphabetic order and to find them using a binary search, so the search function is O(log(n)).

Case sense

Word matching can be case sensitive or not case sensitive. Instead of checking anytime or duplicate the code I decided to use function pointers...

Word recognition

Word recognition is done looking for the left-nearest "space" character. You can easily change your word recognition modifying the line

while (from && buffer[from]!=' ')

with a such line

while (from && buffer[from]!=' ' && buffer[from]!='(' && buffer[from]!='=')

Further improvements (aka TODO)

The learn feature could be improved; anyhow the applicative context suggests different improvement modalities: e.g., you could want to learn only frequent typed words, or only the # nearest words, or....

You could like to display an icon near the word (yes, like Visual Studio)... so you should replace the CArrayString with an array class and a class containing the string and an ID specifying the icon.

Sometimes (when there are many matching words) filling CListBox is slow. It could be useful to replace the CListBox with a faster one (maybe a owner data listbox...)

History

12 July 2002 - First public release