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Chapter: Hello
World Program 1.0
Display
Window
In our Hello World 1.0 program after pressing the Run button you will
notice that a new smaller window was created. This is the Display
Window and because Processing is a visually oriented language it
automatically creates this window which you will usually use to draw to.
The default
Display Window has dimensions 100 pixels in width by 100 pixels in
height and it is automatically created when we run a sketch.
The size() function.
The size() function allows you to specify the dimensions of the Display
Window in pixels. You use the size() function by supplying two
parameters to it, a width value which defines the horizontal dimension
of the Display Window and a height value which defines the vertical
dimension of the Display Window. Just like the println() function,
parameters for the size() function are entered between the function's
parenthesis. For example if we wanted the dimension of the Display
Window to be 640 pixels across by 480 pixels down we would type:
size(640,480);
Note that because we have just entered a statement telling Processing
how big we want the Display Window to be we must terminate this
statement with a semi-colon. You might also have noted that the two
values 640 and 480 are separated with a comma. Do not try to separate
parameter values such as these with a semi-colon because the statement
is incomplete at that point and you are therefore attempting to
terminate it prematurely. This will most commonly result in a syntax
error or even worse in a logical error in some cases.
Parenthesis following a function's name is usually reserved for
parameters relating to the function and these parameters are most
commonly separated by commas. This is pretty easy to remember because
in English you generally list items by separating them with a comma in
Processing and many other higher level languages you separate parameter
values for a function with a comma.
The two values 640 and 480 have been “listed” in this particular order
because when Processing accepts parameters of dimensional type like X
and Y or width and height in 2 dimensions, or X, Y and Z or width,
height and depth in 3 dimensions it will generally accept values in the
order X or width first, Y or height second and Z or depth third. This
is with the exception of a trigonometric function called atan2() in
which Y is read first followed by X due to the special circumstances of
how this function works. Incidentally many other programming languages
besides Processing accept parameters in that particular order for the
atan2() function and in the standard format of X, Y, Z or width,
height, depth for most other functions. Below the first statement type
the second statement so that your code now reads:
println("Hello World");
size(640,480);
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