Subject: bug#65786: 13.2; Indentation problem when left brace is closed with null

From: James Tappin <[email-masked]>
Date: Wed, 6 Sep 2023 16:51:33 +0100

--text follows this line--

When, within an equation environment, a \left\{ is closed with a
\right. as with a display of alternative cases, the \end{equation}
leaves the input indented by one level.

Example:
cumulative sum of the point to point phase shifts, after these are
mapped into $-\pi < \Delta \phi_i \le \pi$, i.e.:
\begin{equation}
  \label{eq:contiguation}
  \phi^{\mathrm{(c)}}_{\mathrm{i}} = \left\{
    \begin{array}[c]{lll}
      \phi^{\mathrm{(c)}}_{\mathrm{i-1}} +
      (\phi_{\mathrm{i}}-\phi_{\mathrm{i-1}}) & \mbox{if}
      & -\pi < \phi_{\mathrm{i}}-\phi_{\mathrm{i-1}} \leqslant \pi \\
      \phi^{\mathrm{(c)}}_{\mathrm{i-1}} +
      (\phi_{\mathrm{i}}-\phi_{\mathrm{i-1}}) - 2 \pi & \mbox{if}
      & \phi_{\mathrm{i}}-\phi_{\mathrm{i-1}} > \pi \\
      \phi^{\mathrm{(c)}}_{\mathrm{i-1}} +
      (\phi_{\mathrm{i}}-\phi_{\mathrm{i-1}}) + 2\pi & \mbox{if}
      & \phi_{\mathrm{i}}-\phi_{\mathrm{i-1}} \leqslant -\pi
    \end{array}
    \right. .
  \end{equation}
  This has the property that there are qualitative changes to the
  behaviour if aliasing occurs.

Not sure if it is as simple as not counting \{ when computing the
indentation or if that would open a whole other can of worms.

Emacs  : GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version
3.24.38, cairo version 1.17.8)
Package: 13.2

current state:
==============
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