getBoundingBox improvements

[padolsey]

What was previously the getComputed method is now getBoundingBox.

It takes on optional argument, a Matrix instance which will be used to apply transforms to the calculated bounding-box.

var shape = new Rect(50, 50, 100, 100);

// No transform applied, -- it'll return the bounding-box
// within shape's own coordinate system:
shape.getBoundingBox(); // ~ 0,0,100,100

// Apply shape's own matrix to the calculation
// (gives position in outer coordinate system):
shape.getBoundingBox( shape.attr('matrix') ); // ~ 50,50,100,100

getBoundingBox always returns an object in the form:

{
  top: n,
  left: n,
  width: n,
  height: n,
  bottom: n,
  right: n
}

Included in this pull request is also an algorithm to determine the correct extrema of cubic bezier curves. Checkout the branch and open the bounding-box.js example to see a demonstration of the new getBoundingBox calculation.

[basecode]

• Afaik we agreed on x and y as aliases for top and left.
• API wise I think we should think about a convenient wrapper for shape.getBoundingBox( shape.attr('matrix') );
  maybe shape.getBoundingBox(true); => I know true says nothing, but you get the point.

[basecode]

Could you add a URL that points to the origin of this approach and if possible add some comments?

[padolsey]

This is the worst part of the implementation because I am not sure how it works. I ported it from a python script I found here: http://blog.hackers-cafe.net/2009/06/how-to-calculate-bezier-curves-bounding.html

I tried understanding the math on the article you linked to but in the end, after struggling, I grabbed this and ported it and it seemed to work.

[klipstein]

@padolsey please add his MIT License note to our LICENSE file.

[iamdustan]

For related issues and discussions:

• getComputed #74 — getComputed
• getComputed('width') doesn't respect borders #2 — getComputed('width') doesn't respect borders
• getComputed() wrong with negative values #116 — getComputed() wrong with negative values

These should all be closable when this is merged.

[davidaurelio]

The doc block still has the key parameter

[davidaurelio]

Awesome demo. I’ve added a few remarks. Can’t verify the bounds algorithm for cubic bezier curves (no time), but it seems to work.

[davidaurelio]

ready for merge? further objections?

[padolsey]

Just to note: This pull request does not fix #2

[iamdustan]

@padolsey very nice demo, indeed! 👍
I think that would be worth adding to http://demos.bonsaijs.org/