deck: A Go package for slide decks

Deck is a library for clients to make scalable presentations, using a standard markup language. Clients read deck files into the Deck structure, and traverse the structure for display, publication, etc. Clients may be interactive or produce standard formats such as SVG or PDF.

Also included is a REST API for listing content, uploading, stopping, starting, uploading and removing decks, generating tables, and playing video.

Elements

• deck: enclosing element
• canvas: describe the dimensions of the drawing canvas, one per deck
• metadata elements: title, creator, publisher, subject, description, date
• slide: within a deck, any number of slides, specify the slide background and text colors.

within slides any number of:

• text: plain, textblock, or code
• list: plain, bullet, number
• image: JPEG or PNG images
• line: straight line
• rect: rectangle
• ellipse: ellipse
• curve: quadraticd Bezier curve
• arc: elliptical arc

Markup

Here is a sample deck in XML:

<deck>
	<title>Sample Deck</title>
	<canvas width="1024" height="768"/>
	<slide bg="maroon" fg="white">
		<image xp="20" yp="30" width="256" height="256" name="picture.png"/>
		<text xp="20" yp="80" sp="3">Deck uses these elements</text>
		<line xp1="20" yp1="75" xp2="90" yp2="75" sp="0.3" color="rgb(127,127,127)"/>
		<list xp="20" yp="70" sp="1.5">
			<li>canvas<li>
			<li>slide</li>
			<li>text</li>
			<li>list</li>
			<i>image</li>
			<li>line</li>
			<li>rect</li>
			<li>ellipse</li>
			<li>curve</li>
			<li>arc</li>
		</list>
		<line    xp1="20" yp1="10" xp2="30" yp2="10"/>
		<rect    xp="35"  yp="10" wp="4" hp="3" color="rgb(127,0,0)"/>
		<ellipse xp="45"  yp="10" wp="4" hp="3" color="rgb(0,127,0)"/>
		<arc     xp="55"  yp="10" wp="4" hp="3" a1="0" a2="180" color="rgb(0,0,127)"/>
	</slide>
</deck>

The list and text elements have common attributes:

xp: horizontal percentage
yp: vertical percentage
sp: font size percentage
type: "bullet", "number" (list), "block", "code" (text)
align: "left", "middle", "end"
color: SVG names ("maroon"), or RGB "rgb(127,0,0)"
font: "sans", "serif", "mono"

See the example directory for example decks.

Layout

All layout in done in terms of percentages, using a coordinate system with the origin (0%, 0%) at the lower left. The x (horizontal) direction increases to the right, with the y (vertical) direction increasing to upwards. For example, to place an element in the middle of the canvas, specify xp="50" yp="50". To place an element one-third from the top, and one-third from the bottom: xp="66.6" yp="33.3".

The size of text is also scaled to the width of the canvas. For example sp="3" is a typical size for slide headings. The dimensions of graphical elements (width, height, stroke width) are also scaled to the canvas width.

The content of the slides are automatically scaled based on the specified canvas size (sane defaults are should be set the clients, if dimensions not specified)

Clients

example client

package main

import (
	"fmt"
	"log"

	"github.com/ajstarks/deck"
)

func dotext(x, y, size float64, text deck.Text) {
	fmt.Println("\tText:", x, y, size, text.Tdata)
}

func dolist(x, y, size float64, list deck.List) {
	fmt.Println("\tList:", x, y, size)
	for i, l := range list.Li {
		fmt.Println("\t\titem", i, l)
	}
}
func main() {
	presentation, err := deck.Read("deck.xml", 1024, 768) // open the deck
	if err != nil {
		log.Fatal(err)
	}
	for slidenumber, slide := range presentation.Slide { // for every slide...
		fmt.Println("Processing slide", slidenumber)
		for _, t := range slide.Text { // process the text elements
			x, y, size := deck.Dimen(presentation.Canvas, t.Xp, t.Yp, t.Sp)
			dotext(x, y, size, t)
		}
		for _, l := range slide.List { // process the list elements
			x, y, size := deck.Dimen(presentation.Canvas, l.Xp, l.Yp, l.Sp)
			dolist(x, y, size, l)
		}
	}
}

Currently there are three clients: vgdeck, pdfdeck and svgdeck.

vgdeck is a program for showing presentations on the Raspberry Pi, using the openvg library. To install:

go get github.com/ajstarks/deck/cmd/vgdeck

To run vgdeck, specify one or more files (marked up in deck XML) on the command line, and each will be shown in turn.

vgdeck sales.xml program.xml architecture.xml

Here are the vgdeck commands:

• Next slide: +, Ctrl-N, [Return]
• Previous slide, -, Ctrl-P, [Backspace]
• First slide: ^, Ctrl-A
• Last slide: $, Ctrl-E
• Reload: r, Ctrl-R
• X-Ray: x, Ctrl-X
• Search: /, Ctrl-F
• Save: s, Ctrl-S
• Quit: q

All commands are a single keystroke, acted on immediately (only the search command waits until you hit [Return] after entering your search text) To cycle through the deck, repeatedly tap [Return] key

For PDF decks, install pdfdeck:

go get github.com/ajstarks/deck/cmd/pdfdeck

pdfdeck produces decks in PDF corresponding to the input file:

pdfdeck deck.xml

produces deck.pdf

For SVG decks, install svgdeck:

go get github.com/ajstarks/deck/cmd/svgdeck

This command:

pdfdeck deck.xml

produces one slide per SVG file, with each slide linked to the next.

The shell script, mktbl creates a tabular layout from tab-separated text

The command sex is a server program that provides an API for slide decks. The API supports deck start, stop, listing, upload, and remove. Responses are encoded in JSON.

To install:

go get github.com/ajstarks/deck/cmd/sex

Command line options control the working directory and address:port

-port Address:port (default: localhost:1958)

-dir [name] working directory (default: ".")

-maxupload [bytes] upload limit

GET / lists the API

GET /deck lists information on content, (filename, file size, modification time) in JSON

GET /deck?filter=[type] filter content list by type (std, deck, image, video)

POST /deck/file.xml?cmd=[duration] starts up a deck; the deck, duration, and process id are returned in JSON

POST /deck/file.xml?slide=[number] start at the specified slide

POST /deck?cmd=stop stops the running deck

DELETE /deck/file.xml removes a deck

PUT or POST to /upload uploads the contents of the Deck: header to the server

POST /table with the content of a tab-separated list, creates a slide with a formatted table, the Deck: header specifies the resulting deck file

POST /table/?textsize=[size] -- specify the text size of the generated table

POST /media plays the media file specified in the Media: header

The command deck is a command line interface to the deck Web API. Install it like this:

go get github.com/ajstarks/deck/cmd/deck

$ deck
Usage:
	List:    deck list [image|deck|video]
	Play:    deck play file
	Stop:    deck stop
	Upload:  deck upload files...
	Remove:  deck remove files...
	Video:   deck video file
	Table:   deck table file [textsize]

The shell script version of the command is in deck.sh. This version uses gttp (go get github.com/dgryski/gttp) to make HTTP requests.