Views

About Views

For a more detailed technical description of the inner workings of declaring a view,
see Appendix A, "The Inside Story on Declare."

Creating a View

3

A view is created in two stages. First, a view memory object (a frame) is created in
RAM. This view memory object contains a reference to its template, along with
other transient run-time information. In the following discussion, the phrase,
"creating the view" is used to describe just this part of the process. Second, the
graphic representation of the view is created and shown on the screen. In the
following discussion, the phrase, "showing the view" is used to describe just this
part of the process.

A view is created and shown at different times, depending on whether or not it is a
declared view.

If the view is declared in another open (shown) view, it is created when the view
in which it is declared is sent the

Open

message. For example, a child view

declared in the parent of its parent view is created when that "grandparent" view
is opened. Note, however, that the child view is not necessarily shown at the
same time it is created.

If the view is not declared in any view, it is created and also shown when its
immediate parent view is sent the

Open

message. (Note that if a nondeclared

view's

vVisible

flag is not set, that view can never be created.)

Here is the view creation sequence for a typical application installed in the Newton
Extras Drawer and declared in the system root view:

1. When your application is installed on the Newton device, its base view is

automatically created, but not shown.

2. When the user taps on the icon representing your application in the Extras

Drawer, the system sends the

ButtonToggleScript

message to the

application's base view.

3. When the application is launched from the Extras Drawer, a view is created (but

not shown yet) for each template declared in the base view. Slots with the names
of these views are created in the base view. These slots contain references to
their corresponding views.

4. The

ViewSetupFormScript

message is sent to the base view,

viewFlags

,

viewFormat

,

viewBounds

,

viewJustify

, and

declareSelf

slots, and so

on, are read from the view template. The global bounds of the view are adjusted
to reflect the effects of the

viewJustifyflags

, but the

viewBounds

values

are not changed, and the

ViewSetupChildrenScript

message is sent to

the base view.