Graphics preview in parallel

[Scott Kostyshak]

On Tue, Jun 23, 2026 at 03:52:12PM +0200, Pavel Sanda wrote:
> Hi all,
> 
> it's my long-term pain to wait for lyx loading the graphics when conversion
> chain is needed for the view. With longer reports with tons of images one has
> to wait while most of the cores are idling. Years back I created some patch
> to parallelize the preview chain, but it kept crashing for strange reason.
> 
> I looked into the issue again now with claude and have decent version which
> does not crash anymore. 

Great! I also have a patch that loads images in parallel that I have
been locally testing for a while. But I don't have a good understanding
and I just hacked things together. Yours seems well thought out.

> 1. The attached code triggers in parallel min(4, #of threads on your machine)
>    conversion chains and thus process the conversions fater. I kept the cap on 4 
>    so we don't overload the machine because of RAM.
>    Might slow initial load times on some machines.
>    I prefer it this way but I could see someone might not like it, objections?

I personally would like the option to be able to increase the threads.
But this can be figured out later.

> 2. I am introducing lfun which would trigger autoload of all previews. I found
>    myself regularly to scroll through the whole document, just that the load
>    process start and I dont have to wait later when working with the rest of
>    document. That's somewhat ridiculous. I do not propose to add this to UI
>    and keep it for power user who can bind it by shortcut.
> 
>    Completely different approach would be just autoload everything on start
>    by default, but I don't like that option - the preview can take on longer
>    documents quite a while and slows down all editation.
> 
>    It's in the second patch, and it does not interfere with the rest of the
>    codebase, so should be less controversial. Currently childern are included,
>    but I am thinking of striping that part.
>    Anyway are there some objections to include this lfun?

Not from me. I also find myself scrolling down just to trigger loading.

Not sure if related, but I also find it annoying that the scrollbar
length is not accurate. I don't like scrolling down and it gets
constantly readjusted as the document is loaded on-the-fly. I would
prefer an option to just have everything load at the beginning.

Okular has a nice "performance" tab of preferences. I attach a
screenshot.

Scott
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