Drawing and Graphics

Using the Drawing Interface

Changes to View Classes

13

The

icon

slot of a view of the

clPictureView

class can now contain a graphic

shape, in addition to bitmap or picture objects.

Using the Drawing Interface

13

This section describes how to use the drawing interface to perform specific tasks.
See "Drawing and Graphics Reference" (page 10-1) in the Newton Programmer's
Reference for descriptions of the functions and methods discussed in this section.

How to Draw

13

Drawing on the Newton screen is a two-part process. You first create a shape object
by calling one or more graphics functions, such as

MakeRect

,

MakeLine

, and so

on. You then draw the shape object by passing any of the shapes returned by the
shape-creation functions, or an array of such shapes optionally intermixed with
style frames to the

DrawShape

method. If a style frame is included in the shape

array, it applies to all subsequent shapes in the array, until overridden by another
style frame.

In addition to the shape object, the

DrawShape

method accepts a style frame

parameter. The style frame specifies certain characteristics to use when drawing the
shape, such as pen size, pen pattern, fill pattern, transfer mode, and so on.

This system is versatile because it separates the shapes from the styles with which
they are drawn. You can create a single shape and then easily draw it using different
styles at different times.

DrawShape

can also accept as its argument an array of shapes instead of just a

single shape. Therefore, you can create a series of shapes and draw them all at once
with a single call to the

DrawShape

method. Additional style frames can be

included in the shape array to change the drawing style for the shapes that follow
them. "Using Nested Arrays of Shapes" (page 13-10), discusses the use of arrays of
shapes in more detail.

Responding to the ViewDrawScript Message

13

When the system draws a view, it sends a

ViewDrawScript

message to the view.

To perform your own drawing operations at this time, you must provide a

ViewDrawScript

method that calls the appropriate drawing functions.

The system also sends the

ViewDrawScript

message to the view whenever it is

redrawn. Views may be redrawn as the result of a system notification or a user action.