Recognition: Advanced Topics

Using Advanced Topics in Recognition

Customized Processing of Input Strokes

10

Setting the

vStrokesAllowed

flag provides the view with a means of intercepting

raw input data for application-specific processing. If this flag is set, strokes are
passed one at a time as the argument to the view's

ViewStrokeScript

method.

Your

ViewStrokeScript

method can then process the strokes in any manner

that is appropriate. The view's

ViewStrokeScript

method is invoked when the

user lifts the pen from the screen at the end of each input stroke.

Both the

vGesturesAllowed

and

vStrokesAllowed

flags invoke methods

that can be used to provide application-specific handling of gestures. However, the

vGesturesAllowed

flag supplies system-defined behavior for the gestures tap,

double-tap, highlight, and scrub in

clEditView

and

clParagraphView

views,

while the

vStrokesAllowed

flag does not provide any behavior that you don't

implement yourself, regardless of the kind of view performing recognition.

For example,

clEditView

and

clParagraphView

views handle system-

defined gestures automatically. Thus, scrubbing in a

clParagraphView

view that

sets the

vGesturesAllowed

flag does not invoke the

ViewGestureScript

method because the view handles this gesture automatically. On the other hand, a

clView

view would need to supply a

ViewGestureScript

method to process

the scrub gesture because this kind of view does not provide any gesture-handling
behavior of its own. Finally, remember that any view setting the

vStrokesAllowed

flag must also supply a

ViewStrokeScript

method.

Setting these flags causes the recognition system to send messages such as

ViewClickScript

or

ViewStrokeScript

, passing a unit (an object that

describes the interaction of the pen with the tablet) as the argument to the
corresponding methods. Units are only valid when accessed from within the
methods invoked during the recognition process--you cannot save them for later
use. However, you can distribute the processing of unit data as appropriate; for
example, you might call the

GetPointsArray

function from within your

ViewClickScript

method and use the result later in your

ViewIdleScript

method.

Do not save units for later use--they are valid only during the
recognition process. After the user interaction is complete and the
various scripts utilizing a particular unit have returned, the
memory allocated for that unit is freed explicitly. Subsequent use
of the unit may produce bus errors or loss of significant data.