Vague open-ended question: it can be useful, at least temporarily and pragmatically, to "simulate" indentations and alignments with as little beginend-, command-, documentclass-, package- and command-overhead as possible.
What do you consider a "good", "robust" way to do so, in LaTeX?
More precise tweak to the question: what do you consider a simple and robust way to tell LaTeX "now insert a horizontal spaces of length precisely lengthof{textpossiblywithsomemathematicsinit}:?
Example of some sort of a solution, but not a good one, it seems to me, due to the use of \textcolor:
This is a line of text containing the greek letter $\pi$.\\
\textcolor{white}{This is a line of text containing the greek letter $\pi$.}And this is a text disjoint from the orthogonal projection of the preceding line of text.
It seems to be preferable to have something like "commandtotakethelengthof(This is a line of text containing the greek letter $\pi$.). Do you think there is a preferred simplest solution?

\hspace{\widthof{.....}}? – Michael Fraiman Jun 20 '17 at 13:27