Bash prompt (PS1) not working as intended

Question

This is my .bashrc file, I'll explain my problem in a bit.

#!/usr/bin/env bash

PS_LINE=`printf -- '  %.0s' {1..200}`

function parse_git_branch {
    PS_BRANCH=''
    PS_FILL=${PS_LINE:0:$COLUMNS}

    if [ -d .svn ] ; then
        PS_BRANCH="(svn r$(svn info|awk '/Revision/{print $2}'))"
        return

    elif [ -f _FOSSIL_ -o -f .fslckout ] ; then
        PS_BRANCH="(fossil $(fossil status|awk '/tags/{print $2}')) "
        return

    elif [ -d .hg ] ; then
        PS_BRANCH="(hg $(hg branch))"
        return
    
    fi

    ref=$(git symbolic-ref HEAD 2> /dev/null) || return
    PS_BRANCH="(git ${ref#refs/heads/}) "
}

PROMPT_COMMAND=parse_git_branch

PS_INFO="$GREEN$USER$RESET@$GREEN$HOSTNAME$RESET:$BLUE\w"
PS_VCS="$YELLOW\$PS_BRANCH"
PS_TIME="\[\033[\$((COLUMNS-10))G\] $RED[\t]"

export PS1="\${PS_FILL}\[\033[0G\]${PS_INFO} ${PS_GIT}${PS_TIME}\n${RESET}\$ "

Ok. So what I want is there's an empty line between my current directory and time (like this). As you can see, that works fine but when I restart my shell (not resource my .bashrc), it looks like this (there's no whitespace between them)

Edit

Based on @chepner answer, I got something like this

Updated code:

function parse_git_branch {
    PS_BRANCH=''
    PS_FILL=${PS_LINE:0:$COLUMNS}

    if [ -d .svn ] ; then
        PS_BRANCH="(svn r$(svn info|awk '/Revision/{print $2}'))"
        return

    elif [ -f _FOSSIL_ -o -f .fslckout ] ; then
        PS_BRANCH="(fossil $(fossil status|awk '/tags/{print $2}')) "
        return

    elif [ -d .hg ] ; then
        PS_BRANCH="(hg $(hg branch))"
        return
    
    fi

    ref=$(git symbolic-ref HEAD 2> /dev/null) || return
    PS_BRANCH="(git ${ref#refs/heads/}) "
}

function set_prompt {
    PS_INFO="$GREEN$USER$RESET@$GREEN$HOSTNAME$RESET:$BLUE\w"
    PS_VCS="$YELLOW\$PS_BRANCH"
    PS_TIME="\[\033[\$((COLUMNS-10))G\] $RED[\t]"
}

PROMPT_COMMAND=set_prompt

export PS1="\${PS_FILL}\[\033[0G\]${PS_INFO} ${PS_GIT}${PS_TIME}\n${RESET}\$ "

Answer 1

Apparently the actual number of columns in the terminal window is assigned to the COLUMNS variable only after the first prompt is issued - I could reproduce this. (It might depend on the time when a window resize signal is handled.) A not quite nice, but effective remedy is to put a delay in .bashrc - for me, sleep .2 worked. Another way is, if the number of columns of the opening terminal is known in advance, to set COLUMNS to that.