Monday, April 10, 2006

Beware of Using AutoComplete for everything

(note: Yes, I know the first version refered to using .T. - it's been updated)

VFP's AutoComplete feature totally rocks. You turn it on and you've immediately provided a valuable tool for any data entry application where repetition is almost always a way of life. So valuable that you might be tempted to turn it on in your base text box class. In a word (ok it's a contraction so maybe two words) , don't.

The reason? AutoComplete works with password fields.

Huh?

AutoComplete has several properties but the most common one is simply to set AutoComplete property to a value other than 0. When this happens, FoxPro "magically" remembers the previous entry and recalls them in a selectable list each time the user comes back into it and enters the same first letter.

This "magic" isn't all that special : default, the file AUTOCOMP (located in your application data folder or current folder for runtime) contains 7 fields: source (the object name), data (the value entered), count (number of times used), weight (if using the value of 4 for AutoComplete), Created timestamp, Updated timestamp and a custom user field. When you enter the key, FoxPro looks into this table (which you can change by specifying the AutoCompTable property) for the object name (which may be overridden with the AutoCompSource property) and then displays it.

The real problem? AutoComplete still runs even when the PasswordChar property is set.

PasswordChar is the property that changes all of the text entered into a text box into that character (typically a star). While you can still refer to the Value property to refer to what the user entered in, the user can't see it directly - it appears like a "password" would in "*****".

BUT if you have AutoComplete set to work (a value of 1,2,3,4) , FoxPro continues to think you want that extra feature turned on. So you have a form prompting for a password, and if your password was FoxPro, as soon as you enter F, FoxPro shows up in the list (not hidden behind the Password character).

Now, in most cases, a developer may have their own txtPassword class or something similar, but it may still be based on a common text class.

Does using AutoComplete make for a good User interface? It's hard to say - many users like it - while others may find it distracting. However, just "trying" it in your application will make this definitely unwanted effect appear.

Consider yourself warned.

I wonder if it's the same with other languages...

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