Teach Yourself Borland C++ in 14 Days - portal

6
204 Day 6
Rest assured that each property knows what it needs to do to present you with the correct
property editor. You will see different types of property editors as you are introduced to new
components and new properties.
The Events Page
The Events page lists all the events that the property is designed to handle. Using the Events
page is pretty basic. In order to create an event handler for an event, you simply double-click
in the Value column next to the event you want to handle. When you do, C++Builder creates
an event-handling function for you with all the parameters needed to handle that event. The
Code Editor is displayed, and the cursor is placed in the event handler. All you have to do
is start typing code. The name of the function is generated based on the Name property of the
component and the event being handled. If, for instance, you had a button named OK and
were handling the OnClick event, the function name generated would be OKClick().
You can let C++Builder generate the name of the event-handling function for you or you can
provide the function name for C++Builder to use. To provide the function name yourself,
type the name in the Value column next to the event and press Enter. The Code Editor is
displayed, and so is the event-handling function, complete with the name you supplied.
Once you have created an event-handling function for a component, you can use that event
handler for any component that handles the same event. Sometimes it’s convenient to have
several buttons use the same OnClick event, for instance. To take it a step further, you might
have a main menu item, a pop-up menu item, and a speedbar button all use the same OnClick
handler. You will learn to appreciate this kind of code reuse as you gain experience with
C++Builder. Even though you are dealing with three different components, they can still
share a common OnClick handler. The Value column of the Events page contains a dropdown
button that can be used to display a list of all event handlers compatible with the current
event. All you have to do is choose an event from the list.
An MDI Sample Program
To help solidify today’s discussion of projects and forms, let’s create an MDI application.
This application will allow you to open and save graphics files like bitmaps, icons, and
metafiles. In order to complete our task, we’ll have to have a master plan. Here’s what we need
to do:
1. Create the main window form (an MDI parent), including a menu.
2. Write code for the File | Open and File | Save menu selections.
3. Write code for the Cascade, Tile, and Arrange All items on the Window menu.