3

The question is in the title.

(needless to say I tried texdoc synctex|etex_man|pdftex|pdftex-a|xetex|luatex and the only thing I found is that it's enabled by the extraprimitives function in LuaTeX. And it looks like one of the internal number registers, but documentation should ideally/hopefully include e.g. can we turn it on and off during the compilation itself/between pages, etc.)

user202729
  • 7,143
  • With some quick testing it appears that locally setting \synctex=0 will not stop the file from being included in the final synctex output. – user202729 Dec 11 '22 at 13:18

1 Answers1

4

extensions.c in the luatex source has

int synctexoption;

/*tex


A convenient primitive is provided: \.{\\synctex=1} in the input source file
enables synchronization whereas \.{\\synctex=0} disables it. Its memory
address is |synctex_code|. It is initialized by the {\sl Sync\TeX} controller
to the command-line option if given. The controller may filter some reserved
bits.

In order to give the {\sl Sync\TeX} controller read and write access to the
contents of the \.{\\synctex} primitive, we declare |synctexoffset|, such
that |mem[synctexoffset]| and \.{\\synctex} correspond to the same memory
storage. |synctexoffset| is initialized to the correct value when quite
everything is initialized.




*/


/tex Holds the true value of |synctex_code|: /

unlike say the primitive corresponding to shell-escape) it is not read-only and may be set locally.

David Carlisle
  • 757,742
  • Given that (if I recalled correctly) the ability to typeset TeX in comments in the source code has not been restored since the source code is converted from web to C, I think this is all there is. Other engine source code may have similar things. – user202729 Dec 11 '22 at 12:58
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    @user202729 texdoc pdftex-changes (and texdoc xetex-changes) has the above quote typeset, in the current version on page 215. – Marijn Dec 11 '22 at 18:21