getBBox() not updating in group's sub-elements after drag

[ghost]

Currently, dragging a group element will have it's getBBox()'s x and y fields updated. However, child elements of the group will have the original x and y coordinates of where it was drawn.

For example:

<g><rect></rect></g>

g's getBBox() will update the x and y on drag, and rect will not.

[ibrierley]

If I'm reading it right, I think this would be expected behaviour.

The rects coordinates (and hence I would assume its getBBox) will be using the container objects (in this case a group element, but could be an svg element for example) coordinate space.

So if you transform the group in this case t250,250 and the original rect is at x,y 10,10 the rect will stay at 10,10 (but be visually at 260,260 if in a typical setup).

[ghost]

I see. Is there a way to get relative x, y of a subelement after transform in a group then? I really just want the position of an item within the group after drag, but having to get the group's transformed position and then having to find the internal position of a subelement seems roundabout.

[ibrierley]

I guess it maybe depends on your end aim, it can be a bit fiddly without a working example. Maybe add g.transform().localMatrix.e & g.transform().localMatrix.f to the elements x,y to find it (assuming no rotations, scales etc) ?

[arunkumar413]

Hi Ian,

How to get the bbox of child when there is rotation on the parent. How to factor the rotation for calculating bbox.

Thanks Arun

[ibrierley]

You would probably have to get the existing transform with getCTM() and then apply it to the various bb points..eg the following I think may return the points

function matrixXY(m,x,y) { return { x: x * m.a + y * m.c + m.e, y: x * m.b + y * m.d + m.f }; }

Element.prototype.getTransformedBB = function() { var m = this.node.getCTM(); var bb = this.getBBox(); var tpts = [ matrixXY(m,bb.x,bb.y), matrixXY(m,bb.x+bb.width,bb.y), matrixXY(m,bb.x+bb.width,bb.y+bb.height), matrixXY(m,bb.x,bb.y+bb.height) ]

return tpts; }

On Tue, Aug 22, 2017 at 6:54 PM, Arun Kumar [email protected] wrote:

Hi Ian,

How to get the bbox of child when there is rotation on the parent. How to factor the rotation for calculating bbox.

Thanks Arun

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