horizontal legend overlaps x-axis title

[salim-b]

The problem occurs if the legend is positioned below (rather than to the right of) the plot area using legend = list(orientation = "h"). It aggravates in combination with multiline x-axis titles (using <br> tags).

Currently there's no way to control the spacing between the legend and the plotting area. Everything is auto-scaled, it is useless to set the bottom margin (margin = list(b = ...)) in this case because it refers to the space below the legend. The only way to make the whole x-axis title visible is to increase the height of the whole plot until the autoscaling sufficiently spreads the legend and the plotting area apart.

I try to illustrate the problem with the following 3 images which differ only in frame height:

height 700px:

height 1000px:

height 1300px:

Here is the above plot hosted on plot.ly.

Update
Due to the suggestion of #812 (comment) I've also reported this over at plotly/plotly.js#1199