slack-thread-full-screenshot.sh

#!/bin/bash

UUID=$(uuidgen)
WORKDIR="$HOME/Desktop/$UUID"
mkdir -p "$WORKDIR"

osascript -e 'activate application "Slack"'
sleep 0.5

i=0
while true
do
    i=$(printf "%.3d" $i)
    filename=$(printf "%.3d.png" $i)
    screencapture -o "$WORKDIR/$filename"
    i=$((i + 1))

    # display dialog
    # if "Cancel" is clicked or ESC key is pressed, the following `osascript` command exits with status code 1 (error).
    # if "OK" is clicked or RETURN key is pressed, the following `osascript` command exits with status code 0 (success).
    if osascript -e 'display dialog "Continue taking screenshot?" default button "OK"' 1>/dev/null 2>/dev/null
    then
        osascript -e 'activate application "Slack"'
        osascript -e 'tell application "System Events" to key code 121' # page down
        sleep 0.5
    else
        break
    fi
done

osascript -e "display notification \"It will open the working folder $WORKDIR soon.\" with title \"Concatenating screenshots\""

convert -append "$WORKDIR/*.png" "$WORKDIR/out.png"
open "$WORKDIR"