Mouse over the screen; a red square fol… by wclang

function u(t) {

c.width=1920 // clear the canvas
for(i=0;i<9;i++)
x.fillRect(400+i*100+S(t)*300,400,50,200) // draw 50x200 rects

} // 122/140

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    u(t) is called 60 times per second.
    t: Elapsed time in seconds.
    S: Shorthand for Math.sin.
    C: Shorthand for Math.cos.
    T: Shorthand for Math.tan.
    R: Function that generates rgba-strings, usage ex.: R(255, 255, 255, 0.5)
    c: A 1920x1080 canvas.
    x: A 2D context for that canvas.

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wclang

function u(t) {

c.onmousemove=function(e){X=e.clientX;Y=e.clientY;}
x.clearRect(0,0,1920,1080);x.fillStyle="red";x.fillRect(3.3*X,3.3*Y,100,100);

Dec 28 2017 7:06 PM UTC

}// 129/140

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Mouse over the screen; a red square follows the mouse.

u/wclang

Note, you'll get an error message until you mouse over the screen.
u/wclang

There's a magic number, 3.3, that keeps the square under the mouse. This doesn't work in full-screen mode (the square is offset from the mouse).
u/wclang

I should mention I learned that mouse events are accessible from FireFly #1629. (I had to figure out what was going on in that dweet, so I could get X and Y off of the mouse.)
u/iverjo

#interactive


      u(t) is called 60 times per second.
      t: elapsed time in seconds.
      c: A 1920x1080 canvas.
      x: A 2D context for that canvas.
      S: Math.sin
      C: Math.cos
      T: Math.tan
      R: Generates rgba-strings, ex.: R(255, 255, 255, 0.5)

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