Improve the accuracy of the docs for beforeMouseDown

[stampyzfanz]

There was a bug in an application I was working on where I used beforeMouseDown to disable panning and it was very hard to debug why it still panned using touch. This change will allow users to know exactly what beforeMouseDown does. Evidence that it doesn't disable panning using touch located in this fiddle: https://jsfiddle.net/thg2brxe/.

[stampyzfanz]

Updating the docs to reflect what it does is a nice first step, but it would also be nice for there to be a documented function that conditionally disables panning when it is initiated via a touch screen as well.

[anvaka]

Thank you for your comment. I agree, the API is not symmetrical which can lead to unmet expectations. We could add beforeTouchDown() to make it symmetrical - would this help?

[taibhse-designs]

Thank you for your comment. I agree, the API is not symmetrical which can lead to unmet expectations. We could add beforeTouchDown() to make it symmetrical - would this help?

For an application I am building, beforeTouchDown would be highly appreciated, I need to be able to disable panning on touch devices unless my canvas has been zoomed into, or atleast be able to disable left right panning,

[stampyzfanz]

Im my project, I ended up editing the source code to get the beforeMouseDown check to both touch events and scroll events. I didn't want the user to be able to pan in any way or scroll while hovering over a button.

Adding a beforeTouchDown would be helpful would assist in this, yes.