Teach Yourself Borland C++ in 14 Days - portal

364 Day 10
At the top of the Forms page is the Main form combo box. This is where you tell C++Builder
which form to display when the application starts. By default, the first form you create will
be the main form. If you change your project in such a way that a different form becomes the
main form, you will need to change this setting so that the new form becomes the
application’s main form.
In the middle of the dialog box, you see two list boxes. The list box on the left is labeled Autocreate
forms; the one on the right is labeled Available forms. Before I talk about how to use
these two list boxes, let’s take a moment to talk about auto-creation of forms.
Each time you create a form, C++Builder places that form in the auto-create list for the
application. Auto-creation means that C++Builder will construct the form during the
application startup process. Forms that are auto-created will display more quickly than forms
that are not auto-created. The disadvantage to auto-creation of forms is that your application
will use more memory than it would if your forms were not auto-created. Another
disadvantage, although probably insignificant, is that your application will take slightly
longer to load if you are auto-creating a lot of forms.
NOTE
The first form in the Auto-create forms list box is always the main
form. If you change the main form, the new form selected will move to
the top of the Auto-create forms list box. Another way to set the main
form is to drag-and-drop any one of the forms in the Auto-create forms
list box to the top of the list.
The nice thing about auto-creation is that displaying an auto-created form is easy. All you
have to do is call that form’s Show() or ShowModal() function:
AboutBox->ShowModal();
If you do not have your forms auto-created by C++Builder, you will have to take the
responsibility of creating the form before you use it:
TAboutBox* aboutBox = new TAboutBox(this);
aboutBox->ShowModal();
delete aboutBox;
This example does not use the C++Builder-generated pointer to the About box. It creates a
local pointer, displays the form, and then deletes the pointer as soon as the form is no longer
needed. As is often the case in C++ programming, there are several ways to perform this
particular task. Because C++Builder always creates a pointer to the form object, I could have
written the previous code like this: