Preload size issue

[valoq]

Sometime text files are shown in the preview only in parts, with the lower half if the lf preview pane being empty.
This appears to be caused by a race condition between the terminal size and lf, where the preload feature runs before the full size has been reached. Consequently it only happens to files that are in the startup directory.

It also does not happen reliably. I noticed recently there were more cases of the lf borders being drawn halfway across the terminal at startup, which may indicate that some changes lead to a slower startup or perhaps its a terminal issue. I will look further into it.

Not sure how to best solve this though

[valoq]

One simple solution would be to use a large default terminal size for the preloaded preview that fits most use cases (like vertical 4k screen with small font) before switching to the real size after the first change of directory. There would be theoretical cases where this issue still persists like very large 8k screen walls with font size 6 but ... it seems to be no worse a solution then the 200ms we currently wait for the preloader.

[valoq]

Tested with lf v41 and git version on foot and alacritty, kitty seems to be unaffected.
Im pretty sure its related to synchronized updates. This was supposedly added in tcell, but it does not actually seem to be the case gdamore/tcell#797 Or do we maybe have to change our tcell implementation? but we actually have to use the feature too :)
afaik kitty and a few other terminal emulators use some sort of hack to avoid these issues but the real solution should use synchronized updates since that is what most terminals support now: https://github.com/contour-terminal/vt-extensions/blob/master/synchronized-output.md

related issue: #1962

[valoq]

After looking into synchronized updates and adding

fmt.Fprint(os.Stderr, "\033[?2026h")
defer fmt.Fprint(os.Stderr, "\033[?2026l")

to the draw() function, this actually solved the issue and probably quite a few others like #1962

Update:
I tested the wrong file and it turns out this didnt fix the preload issue. But Im pretty sure synchronized updates could be used to solve it somehow

[valoq]

I tried setting the timer to 2 seconds

lf/nav.go

Line 687 in 21ac6c1

nav.preloadTimer.Reset(200 * time.Millisecond)

But even that did not fix the issue either, despite lf being ready in far less time, so this timer probably does not work.

Maybe choosing a large default for the starting directory is still the better solution.

Update:
When I remove the line above completely, the bug disappears and the entire preload feature seems to work perfectly.
Removing the line above does not change anything.
Which begs the question if its still needed, or if we should remove the entire timer.

Note: to reproduce the bug, lf needs to be started as the initial terminal application along with the terminal:
$terminal -e lf
The issue is only visible in the starting directory for files that should fill the preview pane for more then half.

[CatsDeservePets]

Could you share a screen recording of the bug happening?

[valoq]

here is a screen recording with an example testfile that has 100 lines. After a moment, "Crtl +r" is used to manually reload lf which shows the real content.
https://github.com/user-attachments/assets/34ac9281-3e6c-44b7-9b98-c44df950f25c

Edit: I keep finding apparent causes and solution but this is just plain unreliable to reproduce. Still looking into it

[valoq]

It seems the solution in #2491 works to address this issue.

I'm still not sure why the delay timer does not work though and that should probably get a closer look as well.