[NTG-context] future versions - synctex

Hans Hagen j.hagen at xs4all.nl
Tue Aug 21 10:33:09 CEST 2018

On 8/21/2018 10:00 AM, Procházka Lukáš Ing. wrote:

> When building a document (or more precisely: documentation which 
> consists of many documents), I'm widely referring to other files via 
> \input, \component etc., I'm widely using \defs, \defines and \buffers 
> defined in separate files (as these defs are used at more places - so 
> let them being defined in one source file) and I'm often generating 
> texts by Lua (e.g. tables - being read and parsed from a text in a 
> \start/\stopluacode block or e.g. Excel named range read via LuaXls or 
> from a .xml - and typeset by a Lua function, which allows simply change 
> all \NC into \VL in a particular place).
> The lengthy process is to EDIT (almost) finished docs/documentation. And 
> at this place, it would be very handy if synctex worked. So I vote for a 
> better click-in-PDF-go-to-source support.

in principle you can push  / pop input states but for such a variety of 
input you have to do that yourself in the styles ... and it will quickly 
become a performance issue then

the core will not get that kind of hard coded synctex flip-flopping

fwiw, the xml sub mechanism does support that kind of functionality as 
option (only because a collegue uses xml with deeply nested inclusions 
spread all over a direcory structure)

> I don't know anything deep about how sync is provided. But my layman 
> point of view would be that whenever a character (or a "box") is to be 
> placed on the page (or into output stream), ConTeXt should know which is 
> the "deepest - currently read" source file, the line, moreover the 
> column - and that position could result into "pick-and-go" position.

only partly ... you don't know where a macro comes from (or what lua 
code generated something) and it makes no sense either to go bakc to 
some macro ... in fact, synctex support in context blocks going to 
styles because those who edit files are not supposed to change styles

things like headers and footers come from styles, not user input

and even much structure stuff comes from elsewhere (like titles of 
sections: they go via lua so there we already need to cheat input 

> In this approach - "boxes" generated by Lua-in-ConTeXt should "jump" on 
> \startluacode, \ctxlua, \cldcommand statement...

won't happen ... way too much overhead and it would polute the source 
too (i follow the principle that any new mechanism that gets added will 
not slow down compilation in a measurable way)

>> Anyway, i can cheat at the tex/lua end if needed and support e.g. titles
>> but i'm not going to pollute the code with every place where we come
>> from lua (also because in most cases there is no relation with the
>> source anyway then). Also, I will not add code that can have an impact
>> on performance when synctex is turned off.
> Synctex should be turned on/off before source files are compiled into 
> PDF - via command line option "--synctex" or 
> \enabledirectives[system.synctex] before \starttext 
> (\enabledirectives[system.synctex] after \starttext (\startcomponent) 
> should be ignored?) - that could cause hooking picked Lua functions (or 
> taking their "synctex-on" alternatives) - so normally (with synctex off) 
> there wouldn't be any performance impact; worse performance would come 
> only with synctex on - but it's user's choice.
>> But for a subset of
>> constructs that are relatively short in usage it is doable (but doesn't
>> really qualify as fun -- also, i don't use it myself).
> Anyway, a better support for "pick-in-PDF-and-go-to-source" (synctex), 
> namely when user "tunes" the docs to their final stage, would be great.
I think that the current approach to hard code synctex libraries into a 
viewer is a limitation (instead an editor should call an external 
program with the page and coordinates so that an external program can 
then look at the synctex file and decide where to go in the editor. That 
way more sophisticated support is possible than the now hard coded 
heuristics. Keep in mind that these heuristics are tuned for latex and 
from context we generate the real minimal amount of synctex code that 
works without clashing with these heuristics. If that were not that case 
is would be unuseable.

Anyhow, there's only so much i can do about it (i'm not going to patch 
viewers). Currently synctex is mostly working for decent structured 
source (can be multiple files).


                                           Hans Hagen | PRAGMA ADE
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        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl

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