Teach Yourself Borland C++ in 14 Days - portal

The C++Builder IDE Explored: Projects and Forms
Step 2: Write Code for the File|Open and
File|Save As Menu Items
So far, so good. Now let’s write the code to implement the File | Open and File | Save As
menu items. C++Builder provides a slick way of writing menu handlers with a minimum
amount of fuss. Keep in mind that we haven’t created the MDI child form yet, but we know
enough about it to write the code for the menu handlers. Here goes:
1. On the main form, choose File | Open from the menu. An event handler is created
for that menu item, and the Code Editor is displayed.
2. Type code so that the event handler looks like this:
NOTE
void __fastcall TMainForm::Open1Click(TObject *Sender)
{
if (OpenDialog->Execute())
{
TChild* child = new TChild(this);
child->SetParent(this);
child->Image->Picture->LoadFromFile(OpenDialog->FileName);
child->ClientWidth = child->Image->Picture->Width;
child->ClientHeight = child->Image->Picture->Height;
child->Caption = OpenDialog->FileName;
child->Show();
}
}
This code first executes the File Open dialog box and gets a filename. If the Cancel
button on the File Open dialog box is clicked, the function returns without doing
anything further. If the OK button on the File Open dialog box is clicked, a new
TChild object is created (TChild will be the name of the MDI child class we’re
going to create later). The image file is loaded into the Image component on the
child form; then the MDI child’s client area is sized to match the size of the image.
Finally, the Caption property is set to the filename selected and the child window is
displayed.
Remember our earlier discussion about calling delete for all objects
created with new? Notice that I appear to be violating that rule in the
preceding code. In reality I am not, because VCL will take the responsibility
of freeing the memory allocated for the MDI child windows.
Notice that the single parameter in the TChild constructor is this. That
tells VCL that the Owner of the MDI child is the MDI form window.
When the MDI form is destroyed (when the application closes), it will
be sure to delete all of its MDI child objects.
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