Tutorial

This tutorial assumes you have access to the slipshow compiler. If you are only interested in trying out slipshow before deciding to install it (or not), you can use the `sliphub editor<sliphub.choum.net/new>`_: it requires no installation on your computer, nor to create any account!

If you do want to use slipshow, we recommand completing the Getting Started part of the document.

Introduction

Slipshow is a compiler from a source file to a source language to a slipshow presentation, so you simply write a text file to describe your presentation. This makes it portable, lightweight and lets you use your favorite text editor instead of forcing you into one. It has also drawbacks: it can be less visual than other solutions such as “power-point” style presentations.

When you turn your source file into a presentation (you compile the presentation), the file created is actually an html file: the format used to describe websites. So, even if it is a local file, you need to open it with a web browser with javascript enabled: most web browsers will work. An important thing to know is that (unless special setup) the file is fully self-contained: it can be viewed offline, and if you want to send your presentation to someone, you just need to send them the file. It is also highly portable: it will work on any OS with a web browser (virtually all of them!).

In this tutorial, you will create your first slipshow presentation. It is entirely self-contained, and introduces both the usage, the syntax and the different features of slipshow. Once you are familiar with the basics, for a complete overview of each of these, you should refer to the reference: the syntax, and API.

A minimal example

We start by considering a simple but complete example. This allows us to cover the basic usage of the tools, the basic syntax, and the basic features of slipshow. The next parts of the tutorial will build on this example to explain the more advanced workflows!

To start, copy the following lines in a file, named for instance prime-numbers.md:

# Prime numbers

What is a prime number?

{pause}

{.definition}
A **prime number** is an integer divisible by exactly two integers: 1, and itself.

Note

The extension of the file (.md) is for markdown. Many editors will open files with such extension in a special mode that will help you read and write it. Slipshow’s syntax is an extension of markdown.

Compiling and viewing your presentation

The file that we just created is the source for a minimal prime-numbers. In order to get the presentation itself, we need to compile it, using the slipshow tool.

This step depends on the way you have access to the slipshow compiler.

In the command palette (Cmd + Maj + P), write Compile slipshow. This will create a file in the same directory, with the same name but the .html extension.

To view this file, opening it in a browser is sufficient! However, the file won’t automatically update to new modifications on your source file. For this, open the command palette again and this time, write Preview slipshow. This will open a preview of the presentation, which will automatically update to the newest changes!

In conclusion: use the preview command when writing your presentation, and use the compile one when your presentation is finished!

On the slipshow preview, you should see the familiar format for slide-based presentations (4:3 rectangle with black borders). Click on it to be sure you have the window focused, and hit the right arrow key (or equivalently, the down-arrow key) to step through the presentation! Right now, it has only two steps: the initial one, and the last one.

Try to make a modification in prime-numbers.md and save the file. The preview should refresh automatically with the new content!

The syntax used

Slipshow uses an extension of Markdown for its main syntax. So, knowing Markdown is a prerequisite to using slipshow. Fortunately, Markdown is very simple! And is already widely used. So instead of explaining the markdown syntax in this tutorial, I’ll link to some great resources to learn Markdown, and only explain the additions:

The Learn Markdown in 60 seconds is from CommonMark, the organization that proposed a well-defined specification for Markdown. They also have a 10-minute tutorial to learn but also train!

The slipshow syntax is defined in syntax. In this tutorial, let’s only focus on the syntax used in the example.

Pauses

The fifth line is the first one that is not regular markdown:

{pause}

This line won’t appear as is in the rendered presentation. In fact, any content inside curly braces {...} is considered “metadata” and will be interpreted in specific ways, but not displayed in the presentation.

The purpose of this line is to inform the slipshow engine that the presentation should “pause” here. Indeed, when opening the presentation, only the title and the first paragraph were shown. The rest of the presentation was shown only after the “right” key was pressed.

Blocks

Following the {pause} keyword, we have the following content:

{.definition}
A **prime number** is a number divisible by exactly two integers: 1, and itself.

The meaning should be clear from the rendered presentation: this is a “definition” block. As you can see, we use the “metadata” syntax once again: the {.definition} part is not rendered, but is used to describe the content. In this case, there is a . followed by a word: such syntax is used for add a “class” to an element, an information which is used only to alter the rendering of an element.

There are several classes available. To describe blocks, in addition to the “definition” block, you can chose from .theorem, .proof, .alert, and .block.

Note

Blocks support the display of a title. You can provide the title in the metadata: {.definition title="Prime numbers"}. Try it in the example!

If your block includes multiple paragraphs or elements, just indent all those elements using >. For instance, try the following in the examples:

{.definition}
> A **prime number** is a number divisible by exactly two integers: 1, and itself.
>
> We consider 1 not to be a prime number, as it is divisible only by one integer.

Your presentation as a papyrus

In the minimal example, we haven’t yet touched the core of slipshow. But we are close to that!

Let’s expand our basic example with the fact and proof that there are infinitely many prime numbers. This is one of the first important fact to know!

Append the following lines to the example file. (If you are dissatisfied with the proof, feel free to improve it 🙂.)

{pause}

{.theorem}
There are infinitely many prime numbers.

{pause .proof}
> Suppose there are finitely many prime numbers.
>
> Let's write $p_0, p_1, \dots, p_{n-1}$ a list of all prime numbers. We define:
>
> ```math
> P = \prod_{i=0}^{n-1}p_i, \quad
> N = P + 1.
> ```
>
> {pause}
>
> Let $p$ be a prime divisor of $N$. We claim that:
>
> ```math
> \forall i, p\neq p_i
> ```
> {pause}
> Indeed,
>
> ```math
> p \text{ divides } N \land\ p\text{ divides } P \implies p\text{ divides } 1
> ```
>
> So $p$ is a prime that is not part of the $p_i$, a contradiction. {pause}
> **Therefore, there must exists infinitely many prime numbers.**

Let’s look at the updated rendering of the presentation: What you see is quite disapointing. There is too many content for the space available, and the last part of the proof overflows and is invisible. Most presentations would solve this problem by creating a new slide, but slipshow does it very differently, which is what makes it unique!

The problem of uncovering new content

Recall the problem here. There is too much content for the space we have: the proof of the infinity of prime numbers overflow through the bottom end!

The usual answer from traditional slideshow programs are to create a new slide to hold the new content. But that does not come without problems. For instance, what to put in this new slide? Obviously, we don’t want to put only the overflown content in the new slide: this content should be seen in some context, that you want to have on screen.

So, one way would be to duplicate some content from the previous slide on the second slide. This works reasonably well, but is often difficult to follow for the viewer: it takes cognitive load to distinguish between what is new and what is just duplicated content in a new slide.

Moreover, it is also a problem for the author: duplicated content means duplicated work when, for instance, rewording the duplicated content.

Slipshow’s way

Slipshow’s solution is to, instead of clearing the whole screen and duplicating some content, just “scroll” the window down to get more space for the new content, hiding only what you do not need anymore!

Let’s focus on our specific case here. We don’t have enough space for the whole proof, but we do not need to see the presentation title, nor the (kind of useless) rhetorical question. However, we do want to keep the “prime number” definition, as long as possible, and the theorem statement as well, of course.

So what we want to do is to “scroll” (I also like the idea of a papyrus being unrolled), until the definition is at the top of the screen. We need two things for that:

  1. Be able to refer to a part of your presentation (in our case, the definition),

  2. Tell the slipshow engine when to move the screen (in our case: when we start displaying the proof),

  3. Tell the slipshow engine where to move the screen (in our case: such that the definition is on top).

Unsurprisingly, all these information are put in the metadatas parts of slipshow syntax: everything enclosed in {}.

Be able to refer to a part of your presentation

For the first point, slipshow uses a system of ids. An id is just a string without space, that must be unique amongst all ids. In order to assign an id to a block, one must adds the id prepended with a # inside the metadata of the block. For instance, let’s add the prime-def id to the definition. The source should look like this now:

{.definition #prime-def}
A **prime number** is a number divisible by exactly two integers: 1, and itself.

Tell the engine when to move the screen

For the second point, we use the at-unpause metadata kind. Such metadata should only be grouped with a pause metadata. It says that a specific action must be taken when stepping through this pause.

Tell the engine where to move the screen

For the third point, slipshow has several commands to move the screen. In our case, we want to put something on top of the screen, so we use up keyword.

Putting everything together

So, we want to add up-at-unpause=prime-def to the pause associated to the proof. The modified source should look like this:

{.definition #prime-def}
A **prime number** is a number divisible by exactly two integers: 1, and itself.

[...]

{pause .proof up-at-unpause=prime-def}
> Suppose there are finitely many prime numbers.
> [...]

Try the rendered version of this new source: by getting rid of anything not useful, there is enough space in the screen to display the definition, theorem statement and whole proof!

The source is still readable, the flow is not broken, and the presentation is easy to follow for the viewer.

Note

The main instructions to move the window are up to put some element on top of the screen, down to put it at the bottom, and center to center it.

If no id is given, the instruction is considered to apply on the element itself. For instance, down-at-unpause without id is a useful command, that we could have used on the proof element.

Note

It is not always best to remove everything that you don’t need. For instance, in the example above, suppose that you continue by giving an example of a very big prime number. Technically, you could start fresh, the example does not need the proof to be on screen. However, for any viewer that is a little bit late, it is very good to keep at least the end of the proof visible, in order to let them finish their note-taking and catch up with the presentation.

Making your presentation live

The previous sections cover most of the first phase of making a presentation: the preparation. Slipshow has also several important features regarding the presentation in itself!

Writing on the screen

One of the design goal of slipshow is to make digital presentations “less bad” compared to the blackboard ones.

One of the great features of boards is that you can write on them while explaining, doodle, make arrows all over the place. To try to do something similar, the slipshow rendering engine allows you to write on your presentation, using the tools present on the top left of your presentation.

The best is still to use the shortcuts:

  • w to write,

  • W to erase,

  • H to erase the highlighted parts,

  • x to go back to a normal cursor,

  • X to clear all annotations.

Add the following content to your presentation, which creates a table in slipshow, following markdown “GFM” syntax:

|1|2|3|4|5|6|7|8|9|10|
|11|12|13|14|15|16|17|18|19|20|
|21|22|23|24|25|26|27|28|29|30|
|31|32|33|34|35|36|37|38|39|40|
|41|42|43|44|45|46|47|48|49|50|
|51|52|53|54|55|56|57|58|59|60|
|61|62|63|64|65|66|67|68|69|70|
|71|72|73|74|75|76|77|78|79|80|
|81|82|83|84|85|86|87|88|89|90|
|91|92|93|94|95|96|97|98|99|100|

and explain the Eratosthenes schema by executing it live!

Starting animations

Many concepts are much easier to understand with animations. I have always been impressed at how scientific popularization video can make very difficult concepts much easier to understand, and also much more fun to learn. There is no point in not using this in our presentations!

Altough slipshow itself does not provide any support for defining animations, it allows you to embed a video, or use any javascript library. For a scripted start and stepping of your animation, you can use the exec-at-unpause attribute, combined with the special slip-script codeblock!

Here is a minimal example of an Eratosthenes animation. It is very dably written, in JS/CSS/HTML, so you need some basic skills on these to understand it, but you can use libraries to make it less tedious.

{#container}

{pause exec-at-unpause}
```slip-script
let d = document.querySelector("#container");
d.style="display: grid; grid-template-columns: repeat(10, auto)";
for(i=1; i<=50 ; i++) {
  let e = document.createElement("div")
  e.style = "border: 1px solid black; padding: 5px ; margin: 5px";
  e.textContent = i;
  d.appendChild(e)
}
```

{pause exec-at-unpause}
```slip-script
let array = document.querySelectorAll("#container > *");
function sleep(ms) {
 return new Promise(resolve => setTimeout(resolve, ms))
}
async function do_(start, w) {
  array[start - 1].style.background="green";
  await sleep(w);
  for(j = start * 2 ; j <= 50 ; j += start) {
    await sleep(125);
    array[j-1].style.background="red";
  }
}
slip.do_ = do_
do_(2, 50)
```

{pause exec-at-unpause}
```slip-script
slip.do_(3, 100)
```

Using the table of content

Press t during a presentation to open the table of content, with fast jump to any part of your presentation!

Moving freely

During a presentation, it is important to not be too tied to the original program. You can move the window freely, using the i, j, k and l keys. Change the “fastness” using the f key.