Apple Newton Utilities Uživatelská příručka stáhnout pdf (Strana 94)

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CHAPTER 3

Views

3-10 About Views

Handling Pen Input 3

The use of the vClickable viewFlags constant to control pen input is

important to understand, so it is worth covering here, even though it is discussed in

more detail in “Recognition” (page 9-1). The

vClickable ﬂag must be set for a

view to receive input. If this ﬂag is not set for a view, that view cannot accept any

pen input.

If you have a view whose

vClickable ﬂag is not set, pen events, such as a tap,

will “fall through” that view and be registered in a background view that does

accept pen input. This can cause unexpected results if you are not careful. You

can prevent pen events from registering in the wrong view by setting the

vClickable flag for a view and providing a ViewClickScript method in the

view that returns non-

nil. This causes the view to capture all pen input within

itself, instead of letting it “fall through” to a different view. If you want to capture

pen events in a view but still prevent input (and electronic ink), do not specify any

other recognition ﬂags besides

vClickable.

If you want strokes or gestures but want to prevent clicks from falling through up

the parent chain, return the symbol

'skip. This symbol tells the view system not

to allow the stroke to be processed by the parent chain, but instead allows the

stroke to be processed by the view itself for recognition behavior.

Several other viewFlags constants are used to control and constrain the recognition

of text, the recognition of shapes, the use of dictionaries, and other input-related

features of views. For more information, refer to “Recognition” (page 9-1).

Location, Size, and Alignment 3

The location and size of a view are speciﬁed in the viewBounds slot of the view

template. The

viewJustify slot affects the location of a view relative to other

views. The

viewJustify slot also controls how text and pictures within the view

are aligned and limits how much text can appear in the view (one line, one word,

and so on).

The

viewOriginX and viewOriginY slots control the offset of child views

within a view.

View Bounds 3

The viewBounds slot deﬁnes the size and location of the view on the screen. The

value of the

viewBounds slot is a frame that contains four slots giving the view

coordinates (all distances are in pixels). For example:

{left: leftValue,

top: topValue,

right: rightValue,

bottom: bottomValue

}

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