The Unofficial Newsletter 
of Delphi Users
March 13th, 1995

by Robert Vivrette

CIS: 76416,1373

Component Design

Component Design is one of the most fascinating aspects of Delphi. I hadn't
even thought of developing my own custom controls in BP7, VB, or C++, yet
with Delphi I have already created 4. Below is my first custom control, so
please be merciful.  I needed a simple currency edit field, and the 
MaskEdit field simply does not cut it. I feel the CurrencyEdit field is a
small step forward in usability. It isn't perfect and can definitely be
improved on.

Essentially, the CurrencyEdit field is a modified memo field. I have put in
keyboard restrictions, so the user cannot enter invalid characters. When the
user leaves the field, the number is reformatted to display appropriately. 
You can left-, center-, or right-justify the field, and you can also specify
its display format - see the FormatFloat command. Since an modifiable
display format is used, it really doesnt even need to hold a currency value.
It could just as easily be a percentage, or a high-precision real value with
fixed digits to the right of the decimal. The field value is stored in a
property called Value so you should read and write to that in your program.
This field is of type Extended.

If you like this control you can feel free to use it, however, if you modify
it, I would like you to send me whatever you did to it. If you send me your
CIS ID, I will send you copies of my custom controls that I develop in the 
future. Please feel free to send me anything you are working on as well.
Perhaps we can spark ideas!