Edge tooltips not behaving correctly, nor matching the documentation

Steps to reproduce

  1. Given the following graph:

tooltip_example.gv

digraph  {
  node1 -> node2 [label="via tooltip, no URL", tooltip="this is a tooltip, via tooltip!"]
  node1 -> node2 [label="via tooltip, with URL", URL="https://gitlab.com/graphviz/graphviz", tooltip="this is a tooltip, via tooltip!"]
  node1 -> node2 [label="via edgetooltip", edgetooltip="this is a tooltip, via edgetooltip!"]
  node1 -> node2 [label="via labeltooltip", labeltooltip="this is a tooltip, via labeltooltip!"]
}

  1. Convert it to an SVG: dot -Tsvg tooltip_example.gv -o tooltip_example.svg

  2. Load the SVG into a web browser to hover with the mouse above each edge and each of their labels, to view their tooltips.

tooltip_example.svg

Expected Behaviour

The edges with an edgetooltip and labeltooltip should show tooltips only on their edge or label, respectively. The two edges defined with a tooltip should show tooltips on both their edges and labels, because the label is part of the edge.

Actual Behaviour

  • Good: The edges with an edgetooltip or labeltooltip behave as expected. Note that this is in constrast to the documentation (https://graphviz.org/doc/info/attrs.html#d:edgetooltip and https://graphviz.org/doc/info/attrs.html#d:labeltooltip), because supposedly these tooltips should only appear if there's a URL defined. Please don't change this behavior! Why should it even matter whether there's a URL? For my use cases, sometimes I don't have a URL but I still want to show a tooltip..

  • Good: The contents of tooltip is indeed always applied to the edge itself (best checked by hovering above the arrows).

  • Bad: The contents of tooltip is never applied to the edge's label, however the label does receive a tooltip containing the contents of the label, if there's a URL defined for that edge. Not only is this redundant (why show the same thing twice?), but also a bit confusing because it's not showing the standard contents.

Long story short, the only way to show a tooltip also on the label for an edge is to define both the tooltip (or edgetooltip) as well as its labeltooltip. It's not a critical bug, but very annoying for maintenance/development.

Documentation Fix

From the attrs.html page, remove both of the following sentences, because they aren't true (nor should they be):

  1. For edgetooltip remove the sentence Used only if the edge has a URL or edgeURL attribute.

  2. For labeltooltip remove the sentence Used only if the edge has a URL or labelURL attribute.

OS Version

Linux

Graphviz Version

$ dot -V
dot - graphviz version 2.43.0 (0)

Related Issues

On first glance, one might see graphviz#1425 (closed) as a duplicate but it's not, because that ticket is only about adding support for tooltips embedded within HTML labels.