In this sample code, the author does the following
\draw ($(closedStart.south) + (-.5em,0)$)
edge[stateEdge] node[edgeLabel, xshift=-3em]{\emph{Passive open}}
($(listen.north) + (-.5em,0)$);
What annoys me the most about these markup-based drawing tools is that I have to measure the value and indicate. In this case, the author indicates .5em
I still do not understand how to understand this? How much is .5em? I don’t even know the size of the base object, since I can be sure that if I give a value, will it be valid?
Is there any approach for this? How do I select a value as well as a block? Is em always the best device to use?
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