如何辨别拖动开始和选择开始HTML5-Canvas

Question

Is there a trivial way to discern between the start of a drag operation, and the start of a select operation on a HTML5-canvas?

I've produced code for both, but both involved setting a boolean with a onmousedown event, processing information when the onmousemove event is fired(if the boolean was set), and then setting the boolean back to false and performing final processing with a onmouseup event. Is there a better way to do either of these?

Thank you for your time, hoping that I was just using the wrong word combinations when trying to Google(as well as looking on stack-overflow) the topic, and sincerely apologize if I missed a post/forum when searching.

Answer 1

When working with mouse primitives, there is no way to know if a mouse-down is part of a click, a double-click, or a drag until a subsequent event is fired.

• A mouse-down followed by a mouse-move is a drag (if the move is greater than some threshold, to allow for human motion while clicking)
• A mouse-down followed by a mouse-up is a click if the time span is too great to be a double-click.
• A mouse-down is a double-click if the down/up/down/up falls withing the double-click threshold.

The difference between a drag and a rect-select is based (usually) on whether or not an object is present under the mouse position when the down is fired.