preventDefault in mousedown suppresses other interactions

[Deepak Anand]

This may have been reported before because it seems like such an obvious issue in many cases.

The event.preventDefault call in the ui/widgets/mouse.js module's _mouseDown and _mouseUp handler prevents other standard interactions from taking place.

For example, i have a canvas-like view where there are draggable DOM elements. The canvas-like view is a simple div which needs to be focused when it's clicked on or its children (the draggable DOM elements) are clicked.

Please let me know if you would like to see a codepen/jsfiddle to understand the issue.

[Deepak Anand]

Since there are no code comments, i am curious to understand the purpose of the many preventDefaults in the code