Use object bounds to filter mouse interactions.

[gskinner]

There have been a number of questions and Pull Requests regarding using object bounds to reduce draws when calculating mouse targets.

This is possible for Bitmap and Sprite, as they have accurate bounds. However, Text, Shape, and Container do not. The first step here should be benchmarking a rough implementation for Bitmap to see how much of a cost savings it offers in that scenario.

Implementation ideas:
We could add DisplayObject.accurateBounds or similar. This would be false by default, and overwritten to true for Bitmap and Sprite. Likewise, it could be set to true when setBounds() is used. We could then do bounds checks for any object that has it set to true.

Container would be fine set to false by default, I don't think there's any performance benefit to calculating the aggregate bounds if we're going to be checking the bounds of the children anyway.

Feedback on this proposal is welcome.

There are others, but here's a couple of examples: #401, #420

[jahooma]

Sounds good! The cost savings for Bitmaps and Sprites should be substantial.

Some thoughts: It might break some people's code if setBounds() automatically sets accurateBounds to true, and then mouse events only work within those set bounds -- I have a feeling people use the built in bounds for a different purpose than they would mouse interaction bounds, e.g. a mostly rectangular shape with some overflowing parts but bounded by that rectangle will be clipped for mouseover events. Maybe setBounds() could take an optional parameter which would override accurateBounds? Or maybe setBounds() should just not affect accurateBounds. Not sure what the best solution is here.

Also, I just wanted to emphasize that setting bounds for containers is a powerful application which many probably won't think to do. Often times we don't know the bounds of the text or shapes, but we do know the bounds of their parent. Moreover, setting the bounds of one container could prevent having to draw or check the bounds of hundreds of children.

Anyway, looks good.
Jahooma

[timm-gs]

We have also looked into this as part of improving hit test performance.

The improvements with doing this on the container were already promising, though I think that might not always be desired, if the container has a child without bounds which then also draws outside of it.

So I followed @gskinner's advice and moved the bounds check only into the DisplayObject branch of _getObjectsUnderPoint and we continue to keep a massive speed up.

So while this might not be working for every user of CreateJS, it's great for our game which is mostly using Bitmap backed objects.