slides

#!/bin/bash

# Copyright (c) 2018 Stanislav Kontar
# License: MIT
#
# Inspired by https://github.com/fxn/tkn

CODE_STYLE="breeze"
SECTION_DECORATION=" ❧❦☙ "
LEN_DECORATION="${#SECTION_DECORATION}"

FORMATTING=(
    "<b>" "$( tput bold )"
    "<s>" "$( tput smso )"
    "<i>" "$( tput sitm )"
    "<u>" "$( tput smul )"
    "<r>" "$( tput sgr0 )"
    "<R>" "$( tput setaf 196 )"
    "<G>" "$( tput setaf 82 )"
    "<B>" "$( tput setaf 39 )"
    "<Y>" "$( tput setaf 226 )"
    "<V>" "$( tput setaf 129 )"
    "<E>" "$( tput setaf 248 )"
)
NR_FORMATTING="${#FORMATTING[@]}"
for (( i = 0; i < NR_FORMATTING; i += 2 )); do
    SED_DELETE+=" -e s/${FORMATTING[i]}//g"
    SED_REPLACE+=" -e s/${FORMATTING[i]}/${FORMATTING[i + 1]}/g"
done

file="${1:-example}"


prepare_terminal() {
    # Get terminal values, clean terminal and remove cursor
    rows=$( tput lines )
    columns=$( tput cols )
    tput clear
    tput civis
}


restore_terminal() {
    # Clean terminal and show cursor again
    tput clear
    tput cnorm
}


read_slides() {
    local i=0

    slides=0  # slides are indexed starting with 1
    slide_starts=()
    slide_lengths=()
    slide_raw_lines=()
    slide_clean_lines=()
    slide_formatted_lines=()

    prepare_terminal

    readarray -t slide_raw_lines < "$file"
    readarray -t slide_clean_lines <<< "$( sed ${SED_DELETE} "$file" )"
    readarray -t slide_formatted_lines <<< "$( sed ${SED_REPLACE} "$file" )"

    while IFS='' read -r line; do
        if [[ "$line" =~ ={40,} ]]; then
            (( slides++ ))
            slide_formats[slides]="$( sed -r -n 's/([a-zA-Z ]*[a-zA-Z])[[:space:]]*={40,}.*$/\1/p' <<< "$line" )"
            slide_starts[slides]="$(( i + 1 ))"
            slide_lengths[slides]=0
        else
            (( slide_lengths[slides]++ ))
        fi
        (( i++ ))
    done < "$file"

    # Remove empty lines at the end of the slide
    for (( i = 1; i <= slides; i++ )); do
        (( start = slide_starts[i] ))
        (( length = slide_lengths[i] ))
        while [[ "${slide_raw_lines[start + length - 1]}" == "" ]]; do
            (( slide_lengths[i]-- ))
            (( length = slide_lengths[i] ))
        done
    done
}


check_slides() {
    local i
    local j

    for (( i = 1; i <= slides; i++ )); do
        (( start = slide_starts[i] ))
        (( length = slide_lengths[i] ))

        # Check if slide fits in the terminal
        if (( length > rows - 2 )); then
            echo "Slide $i too tall."
            return 1
        fi
        for (( j = start; j < start + length; j++  )); do
            if (( ${#slide_clean_lines[j]} > columns - 4 )); then
                echo "Slide $i too wide."
                return 1
            fi
        done
    done
    return 0
}


show_slide() {
    local i

    prepare_terminal

    start="${slide_starts[slide]}"
    length="${slide_lengths[slide]}"
    format="${slide_formats[slide]}"

    # Compute vertical padding
    lines_padding=$(( (rows - length + 1) / 2 ))  # Add 1 to round up

    # Center slide type
    if [[ "$format" == "center" ]]; then
        for (( i = 0; i < lines_padding; i++ )); do
            echo
        done

        for (( i = start; i < start + length; i++ )); do
            # Compute horizontal padding for every line
            filler=$(( (columns - ${#slide_clean_lines[i]} + 1) / 2 ))  # Add 1 to round up

            printf "%${filler}s" " "
            echo -e "${slide_formatted_lines[i]}"
        done

    # Block slide type
    elif [[ "$format" == "block" ]]; then
        for (( i = 0; i < lines_padding; i++ )); do
            echo
        done

        # Compute horizontal padding for whole block
        longest=0
        for (( i = start; i < start + length; i++ )); do
            if (( ${#slide_clean_lines[i]} > longest )); then
                longest=${#slide_clean_lines[i]}
            fi
        done
        filler=$(( (columns - longest + 1) / 2 ))  # Add 1 to round up

        for (( i = start; i < start + length; i++ )); do
            printf "%${filler}s" " "
            echo -e "${slide_formatted_lines[i]}"
        done

    # Code slide type
    elif [[ "$format" =~ code ]]; then
        code=$( sed -r -n 's/^code[[:space:]]+(.*)$/\1/p' <<< "$format" )
        # Perform code formatting
        text=$( for (( i = start; i < start + length; i++  )); do echo -e "${slide_raw_lines[i]}"; done )
        formatted_text=$( highlight -S "$code" -s "$CODE_STYLE" -O xterm256 <<< "$text" )
        readarray -t formatted_lines <<< "$formatted_text"

        for (( i = 0; i < lines_padding; i++ )); do
            echo
        done

        # Compute horizontal padding for whole code block
        longest=0
        for (( i = start; i < start + length; i++ )); do
            if (( ${#slide_raw_lines[i]} > longest )); then
                longest=${#slide_raw_lines[i]}
            fi
        done
        filler=$(( (columns - longest + 1) / 2 ))  # Add 1 to round up

        for (( i = 0; i < length; i++ )); do
            printf "%${filler}s" " "
            echo -e "${formatted_lines[i]}"
        done

    # Section slide type
    elif [[ "$format" == "section" ]]; then
        # Shorter vertical padding because of decorations
        for (( i = 0; i < lines_padding - 2; i++ )); do
            echo
        done

        # Compute horizontal decoration padding
        longest=0
        for (( i = start; i < start + length; i++ )); do
            if (( ${#slide_clean_lines[i]} > longest )); then
                longest=${#slide_clean_lines[i]}
            fi
        done
        line_filler=$(( (columns - longest + 1) / 2 - 1 ))  # Add 1 to round up
        line_length=$(( (longest - LEN_DECORATION + 1) / 2 + 1 ))  # Add 1 to round up

        # Upper decoration
        printf "%${line_filler}s" " "
        for (( i = 0; i < line_length; i++ )); do
            printf "─"
        done
        printf "%s" "$SECTION_DECORATION"
        for (( i = 0; i < line_length; i++ )); do
            printf "─"
        done
        echo
        echo

        for (( i = start; i < start + length; i++ )); do
            # Compute horizontal padding for every line
            filler=$(( (columns - ${#slide_clean_lines[i]} + 1) / 2 ))  # Add 1 to round up
            # Also need to move one char right if line is one character longer
            (( (longest - LEN_DECORATION) % 2 && filler++ ))

            printf "%${filler}s" " "
            echo -e "${slide_formatted_lines[i]}"
        done

        # Lower decoration
        echo
        printf "%${line_filler}s" " "
        for (( i = 0; i < line_length; i++ )); do
            printf "─"
        done
        printf "%s" "$SECTION_DECORATION"
        for (( i = 0; i < line_length; i++ )); do
            printf "─"
        done
    fi
}


show_status() {
    local i

    skip=$(( rows - length - lines_padding - 1 ))
    if [[ "$format" == "section" ]]; then
        (( skip-- ))
    fi
    for (( i = 0; i < skip; i++ )); do
        echo
    done
    status_slide="$slide/$slides [${file##*/}]"
    status_time=$( date +"%-k:%M" )
    status_filler=$(( columns - ${#status_slide} - ${#status_time} - 2 ))
    printf " %s%s%${status_filler}s%s%s" "$( tput setaf 240 )" "$status_slide" " " "$status_time" "$( tput sgr0 )"
}


hide_mouse_cursor() {
    if (( unclutter_installed )); then
        unclutter -idle 1 &
        PID="$!"
    fi
}

show_mouse_cursor() {
    if (( unclutter_installed )); then
        kill "$PID"
        sleep 0.1
    fi
}


# Check if syntax highlighter is installed
if ! command -v highlight &> /dev/null; then
    echo "'highlight' command is required, but not installed. Exiting."
    exit 1
fi

# Check if unclutter is installed
if command -v unclutter &> /dev/null; then
    unclutter_installed=1
else
    unclutter_installed=0
fi

slide=1  # Current slide
status=0  # Status line
read_slides
check_slides
should_show="!$?"

hide_mouse_cursor

while true; do
    # Do not allow current slide number outside bounds
    (( slide < 1 )) && (( slide = 1 ))
    (( slide > slides )) && (( slide = slides ))

    # Only show slide if checks passed
    if (( should_show )); then
        show_slide
        if (( status )); then
            show_status
        fi
    fi

    # Read just one key press
    read -rsn1 response

    # Handle arrows, Page Up, Page Down, Home, End, and ESC
    if [[ "$response" == $'\x1b' ]]; then
        read -rsn1 -t "0.1" response
        if [[ "$response" == "[" ]]; then
            read -rsn1 -t "0.1" response
            if [[ "$response" == "D" || "$response" == "5" ]]; then
                (( slide-- ))
            elif [[ "$response" == "C" || "$response" == "6" ]]; then
                (( slide++ ))
            elif [[ "$response" == "A" || "$response" == "H"  ]]; then
                (( slide = 1 ))
            elif [[ "$response" == "B" || "$response" == "F" ]]; then
                (( slide = slides ))
            fi
        else
            break
        fi
    # Space or Enter, K
    elif [[ "$response" == "" || "$response" == "k" ]]; then
        (( slide++ ))
    # Backspace, J
    elif [[ "$response" == $'\x7F' || "$response" == "j" ]]; then
        (( slide-- ))
    # R
    elif [[ "$response" == "r" ]]; then
        read_slides
        check_slides
        should_show="!$?"
    # B
    elif [[ "$response" == "b" ]]; then
        should_show=$(( ! should_show ))
        prepare_terminal
    # S
    elif [[ "$response" == "s" ]]; then
        (( status = ! status ))
    # Q
    elif [[ "$response" == "q" ]]; then
        break
    # P
    elif [[ "$response" == "p" ]]; then
        # Check if ImageMagick is installed
        if ! command -v import &> /dev/null && ! command -v convert &> /dev/null; then
            echo "ImageMagick is required, but not installed. Export to PDF disabled."
            sleep 2
        # Check if xprop is installed
        elif ! command -v xprop &> /dev/null; then
            echo "'xprop' is required, but not installed. Export to PDF disabled."
            sleep 2
        else
            rm -rf export
            mkdir -p export
            active_window=$( xprop -root 32x '\t$0' _NET_ACTIVE_WINDOW | cut -f 2 )
            for (( slide = 1; slide <= slides; slide++ )); do
                show_slide
                sleep 0.1
                import -window "$active_window" "export/$( printf "%04d" "$slide" ).png"
            done
            convert "export/*.png" "${file}.pdf"
            restore_terminal
            break
        fi
    fi
done

show_mouse_cursor
restore_terminal