Apple Newton Utilities User's Guide download pdf (Page 128)

100

101

CHAPTER 3

Views

3-44 Using Views

To lay out a view containing a vertical column of child views, send the view the

message

LayoutColumn.

Optimizing View Performance 3

Drawing, updating, scrolling, and performing other view operations can account

for a signiﬁcant amount of time used during the execution of your application.

Here are some techniques that can help speed up the view performance of your

application.

Using Drawing Functions 3

Use the drawing functions to draw lines, rectangles, polygons, and even text in a

single view, rather than creating these objects as several separate specialized views.

This technique increases drawing performance and reduces the system overhead

used for each view you create. The drawing functions are described in “Drawing

and Graphics” (page 13-1)

View Fill 3

Many views need no ﬁll color, so you may be inclined to set the ﬁll color to “none”

when you create such a view. However, it’s best to ﬁll the view with white, if it

may be individually dirtied and 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; use this technique only if the view is one that is usually dirtied.

Redrawing Views 3

A view is ﬂagged as dirty (needing redrawing) if you send it the Dirty message,

or as a result of some other operation, such as calling the

SetValue function for a

view. All dirty views are redrawn the next time the system event loop executes.

Often this redrawing speed is sufﬁcient since the system event loop usually

executes several times a second (unless a lengthy or slow method is executing).

However, sometimes you want to be able to redraw a view immediately. The fastest

way to update a single view immediately is to send it the

Dirty message and then

call the global function

RefreshViews. In most cases, only the view you dirtied

will be redrawn.

If you call

RefreshViews and there are multiple dirty views, performance can be

signiﬁcantly slower, depending on where the dirty views are on the screen and how

many other views are between them. In this case, what is redrawn is the rectangle

that is the union of all the dirty views (which might include many other nondirty

1 2 ... 123 124 125 126 127 128 129 130 131 132 133 ... 941 942

Comments to this Manuals

No comments

Apple Newton Utilities User's Guide Page 128

Comments to this Manuals

Related products and manuals for Software Apple Newton Utilities