Views

About Views

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.

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:

,

top:

,

right:

,

bottom:

}