Page 245 - Learn To Program With Scratch

which is exactly what we want. When numList contains data from the user,
calling ShowValues displays the data in those same monitors.
Now let’s explore the Draw procedure, which is executed when
the Painter sprite receives the Draw message. You can see this script in
Figure 9-15.



 224 pixels

−164 −82 0 82 164

Figure 9-15: The Draw script of the Painter sprite

The sprite first sets the pen color. Then it sets the pen’s size to a large
value to draw the thick bars. To prepare for drawing the five vertical bars,
the sprite points in the up direction u.
The script starts a repeat loop to draw the five bars v. We knew the
x-position of each bar in advance, so we created a list named xPos to store
those values (also shown in the figure). During each iteration of the loop,
the Painter sprite moves to the x-position for the current bar, puts its pen
down, and then moves up to draw a vertical line.
The height of each line is
proportional to the correspond-
ing value in numList. Our chart
area on the Stage is 224 pixels tall,
and since 40 is the highest value,
an input of 40 should have a bar
as tall as the chart. To find the
height (in pixels) for any number
in numList, we need to multiply that
number by 5.6 (that is, 224/40).
Figure 9-16 shows the output of
the application after getting some
data from the user. Note that the Figure 9-16: A sample output of the Bar
Frame sprite covers the rounded Chart application
tip of the wide drawing pen so
the bars look flat at the bottom.

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