Optionally limit horizontal, vertical autoScroll

[73rhodes]

Suggestion to add the ability to optionally confine autoScroll in the horizontal or vertical direction.

[taye]

I would think it better to change the speed option to velocityX and velocityY so that a 0 value would disable autoScroll in that axis. The autoScroll method could be kept backwards compatible simply by using the given speed (if any) as the values for velocityX/Y.

[73rhodes]

Good call, let me try that.

[73rhodes]

How would you deal with autoScroll.speed = options.speed ?

[taye]

I'm not sure what you mean. When/how would that happen?

[73rhodes]

That line is within the autoScrollMove function. The speed property is passed on this way, and velocityX / velocityY don't translate easily into a single speed property. This is why simple flags to disable horizontal or vertical scrolling appeared to be the simplest progressive enhancement...

[taye]

That line is actually obsolete. Around line 189 is where changes need to be made to something like this:

var dtx = (now - autoScroll.prevTimeX) / 1000,
    dty = (now - autoScroll.prevTimeY) / 1000,
    vx, vy, sx, sy;

// velocity: { x: pxPerS, y: pxPerS }
if (options.velocity) {
    vx = options.velcoity.x;
    vy = options.velcoity.y;
}
else {
    vx = vy = options.speed;
}

sx = vx * dt;
sy = vy * dt;
...

Perfect backwards compatibility can be maintained. I think that having different X and Y velocities for scroll could be useful but I'm not sure. The only use case that I can think of is extending the current autoScroll so that the scroll velocity depends on the distance to the container edge.

[73rhodes]

Thanks for the suggestion. Implemented and tested; works great!

[pumpknhd]

@taye Does the Velocity option still work? I seem to be unable to restrict the auto-scroll to just the Y axis. Thank you.