A new perl script is spawned each time latexmk is called

[pvonmoradi]

I'm using texlab v3.1.0 alongside coc-texlab with these options:

    // coc-texlab
    "texlab.build.args": [
        "-pdf",
        "-interaction=nonstopmode",
        "-synctex=1",
        "-pvc",
        "%f"
    ],
    "texlab.build.isContinuous": true,
    "texlab.build.onSave": true,
    "texlab.chktex.onOpenAndSave": true,
    "texlab.chktex.onEdit": true,
    "texlab.forwardSearch.executable": "zathura",
    "texlab.forwardSearch.args": [
        "--synctex-forward",
        "%l:1:%f",
        "%p"
    ],

Each time a build command is initiated (manually or by saving the file), a perl script related to latexmk is invoked. Now, since I'm using -pvc switch for a continuous build I also used "texlab.build.isContinuous": true which I thought would prevent these excessive perl scripts which would eventually result in a memory leak.

Here is a screen-cast of the situation:
(Note the htop window with the \tex filter)

Peek.2021-06-03.19-25.mp4

[pfoerster]

Thanks for the very detailed report. The problem is that you should not combine texlab.build.onSave and the -pvc flag at the moment. They basically do the same. -pvc causes latexmk to never stop and run a build each time a document is saved. texlab.build.onSave triggers the build command specified by texlab.build.args, which causes a new instance of latexmk each time. For now, you can set the continous build to false and replace -pvc with -pv. Perhaps, I should include a "fail-safe" to prevent this issue from happening.

[pvonmoradi]

@pfoerster Thanks for your quick reply.
If I use -pv and isContinuous": false, on each build, a new previewer window (Zathura in my case) is spawned instead of it getting updated.
If I use this setting instead:

// coc-texlab
    "texlab.build.args": [
        "-pdf",
        "-interaction=nonstopmode",
        "-synctex=1",
        "-pvc",
        "%f"
    ],
    "texlab.build.isContinuous": false,
    "texlab.build.onSave": false,

It works fine (without re-spawning perl) but I have to issue latex.Build one time to create the previewer window.
Also, It seems "texlab.build.onSave": true, checks the file for diffs faster than the polling mechanism latexmk has implemented. So the above solution causes a ~1 sec delay.

[pfoerster]

It works fine (without re-spawning perl) but I have to issue latex.Build one time to create the previewer window.

From the documentation, I can see that Zathura reloads the file automatically so we do not need to issue another call to the executable when the PDF changes. It looks like #436 needs to be implemented and we need to move away from configuring the PDF viewer in latexmkrc files.

Also, It seems "texlab.build.onSave": true, checks the file for diffs faster than whatever polling mechanism latexmk has implemented. So the above solution causes a ~1 sec delay.

That's because texlab is notified by the editor when a file is saved (textDocument/didSave). latexmk does not have that information. So I think there is definitely a benefit in replacing -pvc.

Thinking about it, I think there is a way to reliably re-implement texlab.build.forwardSearchAfter while we are at it.
I will take a look at it this weekend.

[pfoerster]

texlab 3.2.0 and coc-texlab 3.2.0 have been released in the meantime.
Can you try the latest version with the following settings?

"texlab.build.args": [
    "-pdf",
    "-interaction=nonstopmode",
    "-synctex=1",
    "%f"
],
"texlab.build.forwardSearchAfter": true,
"texlab.build.onSave": true,
"texlab.forwardSearch.executable": "zathura",
"texlab.forwardSearch.args": [
    "--synctex-forward",
    "%l:1:%f",
    "%p"
]    ​

​With this configuration, texlab will recompile your document after saving and keep the viewer synchronized with the cursor.
Note that you do not need a latexmkrc file and the -pv(c) flags anymore.

[pvonmoradi]

@pfoerster Thanks for the new release 😉
Used your config and updated the plugin and binary. Now the output pdf is updated on every save. Moreover, that perl script is not even run once.

A minor problem persists though. Zathura is not executed by the plugin on any of the commands latex.Build or latex.ForwardSearch or saving the file. I have to manually open the output pdf once. Actually, I don't think latex.ForwardSearch is functioning. I've tested this with and without the .latexmkrc file in the project dir.

λ cat .latexmkrc
$pdf_previewer = 'start zathura';

[pfoerster]

@pvonmoradi Can you try running the forward search command

zathura --synctex-forward 42:1:somefile.tex somefile.pdf

manually and see if it works? Did you configure your zathurarc file?

[pvonmoradi]

@pfoerster
I think my zathura is not built with synctex support:
error: Built without synctex support, but synctex specific option was specified.
So the forwardSearch problem is unrelated to texlab.

[pfoerster]

@pvonmoradi Is there anything else that needs to be done from the side of texlab or can we close this issue?