mouseX and mouseY

Programming Questions

jay_m12

in Programming Questions • 1 year ago

Hi guys,

I'm trying to figure out a way to draw two points in a window, the first one being drawn at the x,y position that the mouse is clicked first, and the second one being drawn at the x,y position of the second mouse click.

For example, you would click at the position (10,10), and an ellipse would be drawn at that point and stay there;

Then you would click at the position (150,200) and an ellipse would be drawn at that point and stay there.

I've tried doing this many different ways, using mousePressed(), mouseClicked(), mouseX, mouseY, pmouseX and pmouseY, and I'm able to draw the initial point at the originally clicked position, but as soon as I click on a new position for the second point, the first one moves to that point as well.

I'm having trouble figuring out a way to get the first point to stay in it's original clicked position and to get the second point to stay in it's own clicked position.

Any ideas on what I can do?

Replies(4)

jbum

Re: mouseX and mouseY

1 year ago

Stop clearing the background in your draw routine.

This will keep the first ellipse from "moving". In other words:

void setup()

{

size(800,600);

background(255); // <-- clear background here

}

void draw()

{

// <-- and not here

ellipse(mouseX, mouseY, 20, 20);

}

If that doesn't fix it, post your code.

jay_m12

Re: mouseX and mouseY

1 year ago

That does exactly what I needed it to, but I've come across another problem.

In order to draw a rectangle using the line between two points as its diagonal, I need some way to save the x,y positions of the two points, yet they're both set to be mouseX and mouseY.

Is there a way to "freeze" a mouseX or mouseY value into a variable for future use?

jbum

Re: mouseX and mouseY

1 year ago

Yes. It's awkward to do this the draw routine, because it is constantly being called, even when you're not clicking on the mouse (and it is called repeatedly even during the brief instant you are holding the mouse button down). It's better to use a mousePressed() function - thus function (or "event handler") will only get called once per mouse click.

This sketch shows the basic idea. I'm using two global variables to store the last position of the mouse. The variables are declared outside any of the functions (or "globally") so that they don't get reinitialized on each call of the function, as interior or "local" variables do.

int lastMouseX = -1;
int lastMouseY = -1;
void setup()
{
size(800,600);
}
void draw()
{
}
void mousePressed()
{
ellipse(mouseX, mouseY, 20, 20);
if (lastMouseX != -1) {
line(lastMouseX, lastMouseY, mouseX, mouseY);
}
lastMouseX = mouseX;
lastMouseY = mouseY;
}

jay_m12

Re: mouseX and mouseY

1 year ago

That's perfect!

Thanks for the help

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