86 CHAPTER 7. GRAPHICAL USER INTERFACE DESIGN IN SCHEME

yellow

(color 255 255 0)

white

(color 255 255 255)

black

(color 0 0 0)

blue

(color 0 0 255)

lightblue

(color 200 200 255)

darkblue

(color 0 0 150)

You can set the background of a label (or any other component) just by including

the color as one of the arguments of the label. Continuing with our running

example, we can make the label yellow as follows:

(define w

(window "Hello"

(label "Hello again" (HelveticaBold 60) yellow)))

(.pack w)

(.show w)

7.7

Tabular Layouts

So far we have considered windows containing a single label. We now look at

four procedures for specifying the layout of multiple components in a window.

Although these layouts can be applied to any component, we will stick with

labels for simplicity.

The first two layouts we discuss are the row and column layouts. The row

procedure arranges its arguments horizontally across the window. The col

procedures arranges its arguments vertically. For example, the following code

produces a window with labels  red ,  green ,  yellow , and  blue  having the

same color as their label, laid out horizontally across the window:

(define w

(window "Hello"

(row

(label "red" red)

(label "green" green)

(label "yellow" yellow)

(label "blue" blue)

)))

(.pack w)

(.show w)

By swapping  col  for  row , the labels would be arranged vertically.

The row and col procedures also take additional arguments which specify

what should happen when the window is resized. One possibility is to have the

components in the row stay the same size even though the window grows. On

the otherhand, one might want the components in the row to expand as the

window expands (the expansion can be horizontal, or vertical, or both). To

specify this expansion property one adds one of the following to the row or col

argument lists: