Teach Yourself Borland C++ in 14 Days - portal

338 Day 9
WARNING
NOTE
Placing any code between the published keyword and the private
keyword can cause problems with your program. In some cases, you
might just get compiler or linker errors. In other cases, your program
might be beyond repair (unusual but possible). Get in the habit of
avoiding the published section like the plague.
If you’re an astute student, you may be scratching your head right now.
In the first four chapters we covered the basics of the C++ language.
You learned about private, protected, and public class access, but not
a word about the published keyword. The reason is simple: published
is not a C++ keyword. The published keyword is a Borland extension
to C++ and doesn’t exist in ANSI standard C++. This keyword was
added to allow the C++ language to take advantage of the power of
components.
Notice that lines 59 and 60 in Listing 9.1 have comments that say User declarations. You
can safely place any of your own class data members or class member function declarations
in either the private or the public section of the class declaration.
A Word About Status Bars and Hints
In a moment we’re going to add support for hint text displayed in the status bar of the
ScratchPad program. Before we do, though, you need a brief primer on how hint text is
handled.
When the Application object’s ShowHint property is set to true (the default), and the mouse
cursor is placed over a component that also has its ShowHint property set to true, a hint event
is triggered. The Application object has an event called OnHint that occurs whenever a hint
event is triggered. The Application’s Hint property will contain the hint text for the control
that generated the hint event. An application can use the OnHint event to display the hint on
a status bar.
The problem is that you can’t directly access the OnHint event of the Application object.
What you can do, however, is reassign the value of OnHint to point to one of your own
functions. Then, when the hint event occurs, the event gets rerouted to your own OnHint
handler. To do that, you have to write your own event handler for the OnHint event. Let’s do
that next.