Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 535)

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CHAPTER 13

Drawing and Graphics

Using the Drawing Interface 13-9

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.

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Apple Newton Utilities Guide de l'utilisateur Page 535

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