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PegPresentationManager. Next() would return PegWindow2. Since all lists are

terminated with a NULL, Previous() would return NULL. So, if we wanted traverse all

of the children of an object, we could use the following code:

PegThing *pTest = Parent()->First(); // first child of my parent

int iSiblings = 0;

// Since all lists are NULL terminated,

// we can loop on while ptest!=NULL

while(pTest)

{

if (pTest != this)

{

iSiblings++;

}

pTest = pTest->Next();

}

Adding to and Removing from the Tree

PEG provides two functions to add PegThings to the presentation tree:

void PegThing::Add(PegThing *Who, BOOL bDraw = TRUE);

void PegThing::AddToEnd(PegThing *Who, BOOL bDraw = TRUE);

Add() always adds the child to the beginning of the linked list of children. If you would

like to add to the end, use AddToEnd().

Let’s look at some example code and see what the tree it creates will look like:

PegRect Rect(10, 10, 40, 40);

PegWindow *child_window = new PegWindow(Rect);

PegWindow *parent_window = new PegWindow(Rect + 50);

PegPrompt *prompt1 = new PegPrompt(0, 0, “Prompt1”);

PegPrompt *prompt2 = new PegPrompt(0,30, “”Prompt2”);

prent_window->Add(child_window);

child_window->Add(prompt1);

child_window->AddToEnd(prompt2);

child_window

rompt1

rompt2

arent_window

There are also two functions to remove an object from the tree:

Casio ClassPad 300 Programming Guide

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