Change mouseX/mouseY handling

[mattdesl]

Hello!

This changes the way mouse and touch values are stored to address the following two tickets:
#1176
#1269

Currently, mouseX and mouseY values are always lagging behind the real system values when the mouse is moving.

The new approach works like this:

• On mouse events, set the mouseX and mouseY values so that they represent the actual mouse value at that event
• After we draw() a frame, we set the pmouseX and pmouseY to the value of mouseX and mouseY, the next time the draw is called it will have the previous mouse position
• The first time we change mouseX and mouseY, we also set the pmouseX/pmouseY to the same value. This way they don't start at (0, 0) which is a bit arbitrary.
• Same logic applied for touch events and pwinMouseX / pwinMouseY

Some tests, I'm using the p5js editor.

Example 1

function setup() {
  createCanvas(windowWidth, windowHeight);
}

function draw () {
  line(mouseX, mouseY, pmouseX, pmouseY);
}

Before PR:

After PR:

Example 2

function setup() {
  createCanvas(windowWidth, windowHeight);
}

function mouseMoved() {
  ellipse(mouseX, mouseY, 50, 50);
}

Before PR:

After PR:

Let me know what you think! 😄

[lmccart]

this is great and makes a lot of sense, thank you!