support headlabel and taillabel under tikzedgelabels

[bharath-ravindranath]

As documented in https://dot2tex.readthedocs.io/en/latest/customization_guide.html#customizing-edges

The headlabel and taillabel attributes are currently not affected by the tikzedgelabels option.

Can this support be added? While creating network diagrams, I am trying to add both ends of the interface as head/tail label. The Graphviz does not support rotating any label. But dot2tex can support this (and fairly easily)

Possible Solution:

Currently the generated Latex file will have the following if lblstyle='above, sloped' is configured in dot Graph file.

  \draw [] (53.916bp,143.83bp) .. controls (48.5bp,133.0bp) and (41.644bp,119.29bp)  .. (36.207bp,108.41bp);
  \definecolor{strokecol}{rgb}{0.0,0.0,0.0};
  \pgfsetstrokecolor{strokecol}
  \draw (44.195bp,136.83bp) node[above, sloped] {Et2};
  \draw (26.486bp,115.41bp) node[above, sloped] {Et1};

based on the co-ordinates used to draw the line i.e (53.916bp,143.83bp) and (36.207bp,108.41bp), we can calculate the angle of the line using: math.degrees(math.atan2((53.916,143.83),(36.207,108.41)) using this angle, we can update the above Latex to include the angle (rotate=<degrees calculated>):

  \draw [] (53.916bp,143.83bp) .. controls (48.5bp,133.0bp) and (41.644bp,119.29bp)  .. (36.207bp,108.41bp);
  \definecolor{strokecol}{rgb}{0.0,0.0,0.0};
  \pgfsetstrokecolor{strokecol}
  \draw (44.195bp,136.83bp) node[rotate=63.43] {Et2};
  \draw (26.486bp,115.41bp) node[rotate=63.43] {Et1};