Zero width

Programming Questions

hatsaresi..

in Programming Questions • 1 year ago

Why does this code print "0" for the variable dwidth?

void setup () {
size(1900, 1020);
background(0);
}

int dwidth = width;

void draw() {
println(dwidth);
}

Replies(4)

tfguy44

Re: Zero width

1 year ago

// "width" has no value until after size() is called.

// But global variables are defined before setup() is run!
int dwidth = width;

int ewidth;

void setup () {
size(1900, 1020);
background(0);

ewidth = width;
}

void draw() {
println(dwidth);
println(ewidth);

}

hatsaresi..

Re: Zero width

1 year ago

But in my code, dwidth=width; comes after void setup(), should it not have already been called?

tfguy44

Re: Zero width

1 year ago

No. Things aren't executed in the order that you type them. Functions run at specific times.

First thing's first: Global variables - those defined outside of any function - are defined. They are global because they are not inside a function. Where they are located relative to functions being defined doesn't matter.

Then setup() runs once when the program starts.

When the program needs to refresh what is seen in the window, draw() is called.

If the mouse is clicked, mouseClicked() is called.

If a key is pressed, keyPressed() is called.

And so on...

These functions are event-driven. The order that you list then in doesn't matter.

In any case, global variables won't be able to access the value of width.

To set a global variable to width, do as I have shown with my variable ewidth.

hatsaresi..

Re: Zero width

1 year ago

Ok, that clears things up. Thanks a lot!

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