Node coordinates

[kalliopeargentina]

Hi, I've been experimenting with your program (awesome by the way) and added some features I needed for my app for personal use (i added some display filters and touch gestures). I was thinking of adding a feature to add nodes and edges (ie: adding a node where I click with the mouse or tap). If this is likekly to happen I would need to understand how do you map position from the gexf coordinates to the canvas. I see that you use a function called calcCoord but I am not understanding how it works. could you provide some pointers or general ideas so I can understand this? what i would try to make is an inverse function so i can get the gexf coordinates from the mouse position.

By the way if you are curious about my app here is a link (its in spanish):

http://www.kalliope.com.ar/gexf-js-master/index.html

And an article explaining it (sadly also in spanish only):

http://vikingobjj.blogspot.com.ar/2014/01/war-inside-my-head.html

[raphv]

Hello,

There is a function called nodeFromPos that looks up nodes at the mouse position.

I know the code for that part is a bit complicated and tends to mix french and english and that the words I use to describe coordinate properties may be improper.

The coordinates are transformed 3 times to convert node positions from the Gexf file to screen positions:

1 - First, when the GEXF file is loaded, the coordinates are normalised, that gives the coords.base property https://github.com/raphv/gexf-js/blob/master/js/gexfjs.js#L442
2 - Then, when the scale is changed, the coordinates are recalculated to what I call coords.actual https://github.com/raphv/gexf-js/blob/master/js/gexfjs.js#L611
3 - Finally, and only if the lens mode is activated, the node positions that are under the lens are transformed again to coords.real https://github.com/raphv/gexf-js/blob/master/js/gexfjs.js#L663

I hope this helps,

Regards,

Raphael

[kalliopeargentina]

Thanks! I'll let you know how it goes