forgit: Delta side-by-side not displayed correctly on fzf preview window

A workaround based on @Kr1ss-XD 's comment:

NOTE I’ve just noticed a paragraph in the fzf(1) manual, which might be relevant for this ticket :

fzf exports $FZF_PREVIEW_LINES and $FZF_PREVIEW_COLUMNS so that they represent the exact size of the preview window. (It also overrides $LINES and $COLUMNS with the same values but they can be reset by the default shell, so prefer to refer to the ones with FZF_PREVIEW_ prefix.)

It’s in the “Preview” section.

export FORGIT_PAGER='delta --side-by-side -w ${FZF_PREVIEW_COLUMNS:-$COLUMNS}' 

<strike>The only cons of this solution is it need to be set manually instead of reading from git’s config automatically. </strike>

EDIT: You can also make it work by changing git’s config:

pager = delta --side-by-side -w ${FZF_PREVIEW_COLUMNS:-$COLUMNS}

@mrswats @crivotz

@wfxr this worked for me

[core]
pager = bash -c 'delta --side-by-side --width ${FZF_PREVIEW_COLUMNS:-$COLUMNS}'

it seems that git uses sh to run this command, and ${var:-word} is a bashism, so this explicitly uses bash

@mrswats Thanks for your help and suggestion. I will pin this issue (until it gets fixed more elgantly) so that others with the same problem will easily find the solution.

BTW I like delta’s side-by-side view but it is not suitable when the window is narrow. So I use the following config that can auto switch to the classic view when the with of window is less than 160. Hope it can help you too.

pager = "{ [ $COLUMNS -lt 160 ] && delta || delta --side-by-side -w ${FZF_PREVIEW_COLUMNS:-$COLUMNS}; }"

EDIT: A little more complicated but better config:

pager = "{                                                           \
    COLUMNS=$(tput cols);                                            \
    if [ $COLUMNS -ge 80 ] && [ -z $FZF_PREVIEW_COLUMNS ]; then      \
        delta --side-by-side -w $COLUMNS;                            \
    elif [ $COLUMNS -ge 160 ] && [ ! -z $FZF_PREVIEW_COLUMNS ]; then \
        delta --side-by-side -w $FZF_PREVIEW_COLUMNS;                \
    else                                                             \
        delta;                                                       \
    fi                                                               \
}"

Nice ! If that is the issue, it might also suffice to simply omit the : :

[core]
	pager	=	delta --side-by-side --width ${FZF_PREVIEW_COLUMNS-$COLUMNS}

I think that’s valid sh syntax. Not tested though - I’m on mobile right now.

Okay, just right after comenting the other issue the first open issue in delta is this one: https://github.com/dandavison/delta/issues/368 which is exactly the issue I reported.

@0xRZ Have you exported your FZF_PREVIEW_COLUMNS and COLUMNS variables? Otherwise forgit has no access to them.

This solution stopped working for me on fzf 0.35.1, delta 0.15.1: pager = delta --width ${FZF_PREVIEW_COLUMNS-$COLUMNS}

It says error: The argument '--width <N>' requires a value but none was supplied when trying to open diff with forgit::diff