Apple Newton Utilities User's Guide download pdf (Page 105)

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CHAPTER 3

Views

About Views 3-21

IMPORTANT

Many views need no ﬁll pattern, so you may be inclined to set the

ﬁll pattern to “none” when you create such a view. However, it’s

best to ﬁll the view with white, if the view may be explicitly

dirtied (in need of redrawing) and if you don’t need a transparent

view. This increases the performance of your application because

when the system is redrawing the screen, it doesn’t have to update

views behind those ﬁlled with a solid color such as white.

However, don’t ﬁll all views with white, since there is some small

overhead associated with ﬁlls; only use this technique if the view

is one that is usually dirtied.

Also, note that the application base view always appears opaque,

as do all child views of the root view. That is, if no ﬁll is set for

the application base view, it automatically appears to be ﬁlled

with white.

▲

The view format attributes are listed and described in Table 2-5 (page 2-13) in the

Newton Programmer’s Reference.

Custom Fill and Frame Patterns 3

Custom ﬁll and custom view frame patterns are set for a view by using the

vfCustom flag, as shown in Table 2-5 (page 2-13) in the Newton Programmer’s

Reference, and by using following two slots:

viewFillPattern

Sets a custom ﬁll pattern that is used to ﬁll the view.

viewFramePattern

Sets a custom pattern that is used to draw the frame lines

around the view, if the view has a frame.

You can use custom ﬁll and frame patterns by setting the value of the

viewFillPattern and viewFramePattern slots to a binary data structure

containing a custom pattern. A pattern is simply an eight-byte binary data structure

with the class

'pattern.

You can use this NewtonScript trick to create binary pattern data structures “on

the ﬂy”:

DefineGlobalConstant('myPat,SetLength(SetClass(Clone

("\uAAAAAAAAAAAAAAAA"),'pattern), 8));

This code clones a string, which is already a binary object, and changes its class to

'pattern. The string is specified with hexadecimal character codes whose binary

representation is used to create the pattern. Each two-digit hex code creates one

byte of the pattern.

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