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>> SPEAKER 1: Let's write a program that
has a graphical user interface that

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includes a slider that a user can move
left to right in order to choose some

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value between two integers.

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>> To do so, I've begun with
some placeholder code.

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And now let's fill in a blank.

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Let's first allocate a GSlider, calling
it slider, and assign to it

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the return value of getGSlider.

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And now let's specify that I want the
lower bound of the slider to be an

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integer of 0, the upper bound of the
slider to be an integer of 100, and

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the default initial value to be 50.

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>> Next, let's go ahead and associate an
action command with this slider by

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calling setActionCommand, passing in
slider, and passing in an arbitrary

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but unique string like quote unquote
"slide." In other words, "slide" is

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going to be the identifier uniquely
associated with this slider.

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Just in case my user interface had
multiple sliders, I could distinguish

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among them with this technique.

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>> Next, let's call addToRegion, passing in
window, passing in slider, passing

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in quote unquote "SOUTH," in order to
add the slider to the southernmost

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region of our user interface.

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Where quote unquote "SOUTH" happens to
be unique identifier defined in the

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Stanford Portable Library.

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>> But now, for clarity, to the left
of the slider let's hard

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code the number 0.

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And to the right of the slider let's
hard code the number 100.

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So that the user knows by sliding the
thing to the left or to the right how

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they're changing its value.

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>> Before we allocate that slider, let's
go back here and allocate a GLabel,

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calling it left.

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And assign it the return value of
newGLabel, passing in quote unquote--

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in other words--

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of "0." Let's now call addToRegion,
passing in window, passing in left,

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passing in quote unquote "SOUTH." So
that this label is inserted into that

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southern region before the slider.

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>> And now after the slider, let's go
ahead and declare another GLabel.

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Calling it right, assigning it the
return value of newGLabel.

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Quote unquote-- another string--

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"100." And then call addToRegion,
passing in window, passing in right,

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passing in "SOUTH" as well.

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In other words, we've just declared a
label, a slider, and another label and

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inserted them into the southern region
in that order, so that the user knows

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when he or she moves it to the right
or to the left roughly what value

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they'll be approaching.

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>> Let's now induce an infinite loop.

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And inside of this loop,
lets first check for a

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GActionEvent, calling it event.

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Assigning it the return
value of waitForEvent.

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Passing in ACTION-EVENT, a constant
declared in the Stanford Portable

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Library that indicates that you indeed
want to wait for an action.

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>> Let's next check if getEventType,
passing in event, equals

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WINDOW_CLOSED, another constant declared
in the Stanford Portable

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Library that indicates that the action
is the closing of a window.

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Then let's go ahead and break out
of this otherwise infinite loop.

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>> Else, let's check if the user
has slid that slider.

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If string compare of getActionCommand,
passing in event, comma, quote unquote

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"slide" equals equals 0.

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In other words, if the unique identifier
associated with the slider

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that has been slid equals quote unquote
"slide," the unique identifier

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that we provided earlier, then
I want to do the following.

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>> Printf "slider was slid to %i backslash
n," indicating that I'd like

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to plug in the integral
value of the slider.

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So comma getValue of slider.

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>> Let's now save, compile, run this
program, and slide that slider.

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Make slider.

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./slider.

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There's my user interface.

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There's my slider, to the left of which
is a 0, to the right of which is

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100, both of them labels.

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And as I slide the slider to the left
and the right, notice that in my

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console window I'll see
the integer value.

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>> Now, I don't necessarily see all of the
numbers between 0 and 100, because

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depending on the speed with which
I move the slider, my

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program might not notice.

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But indeed, if I move it to any
particular location, that's the value

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that will print.

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