/touying-author

Complex Animations

Thanks to the syntax provided by Polylux, we can also use only, uncover, and alternatives in Touying.

Mark-Style Functions

We can use mark-style functions, which are very convenient to use.

At subslide #touying-fn-wrapper((self: none) => str(self.subslide)), we can

use #uncover("2-")[`#uncover` function] for reserving space,

use #only("2-")[`#only` function] for not reserving space,

#alternatives[call `#only` multiple times \u{2717}][use `#alternatives` function #sym.checkmark] for choosing one of the alternatives.

However, this does not work in all cases, for example if you put uncover into the context expression, you will get an error.

Callback-Style Functions

To overcome the limitations of layout functions mentioned earlier, Touying cleverly implements always-effective only, uncover, and alternatives using callback functions. Specifically, you need to introduce these three functions as follows:

#slide(repeat: 3, self => [
  #let (uncover, only, alternatives) = utils.methods(self)

  At subslide #self.subslide, we can

  use #uncover("2-")[`#uncover` function] for reserving space,

  use #only("2-")[`#only` function] for not reserving space,

  #alternatives[call `#only` multiple times \u{2717}][use `#alternatives` function #sym.checkmark] for choosing one of the alternatives.
])

image

Notice that we no longer pass a content block but instead pass a callback function with a self parameter. Later, we extract only, uncover, and alternatives functions from self using:

#let (uncover, only, alternatives) = utils.methods(self)

We then call these functions in subsequent steps.

Here's an interesting fact: the self.subslide of type int indicates the current subslide index, and in fact, the only, uncover, and alternatives functions rely on self.subslide to determine the current subslide index.

:::warning[Warning]

We manually specify the repeat: 3 parameter, indicating the display of 3 subslides. We need to do this manually because Touying cannot infer how many subslides only, uncover, and alternatives should display.

:::

only

The only function means it "appears" only on selected subslides. If it doesn't appear, it completely disappears and doesn't occupy any space. In other words, #only(index, body) is either body or none.

The index can be an int type or a str type like "2-" or "2-3". For more usage, refer to Polylux.

uncover

The uncover function means it "displays" only on selected subslides; otherwise, it will be covered by the cover function but still occupies the original space. In other words, #uncover(index, body) is either body or cover(body).

The index can be an int type or a str type like "2-" or "2-3". For more usage, refer to Polylux.

You may also have noticed that #pause actually uses the cover function, providing a more convenient syntax. In reality, their effects are almost identical.

alternatives

The alternatives function displays a series of different content in different subslides. For example:

#slide(repeat: 3, self => [
  #let (uncover, only, alternatives) = utils.methods(self)

  #alternatives[Ann][Bob][Christopher]
  likes
  #alternatives[chocolate][strawberry][vanilla]
  ice cream.
])

image

As you can see, alternatives can automatically expand to the most suitable width and height, a capability that only and uncover lack. In fact, alternatives has other parameters, such as start: 2, repeat-last: true, and position: center + horizon. For more usage, refer to Polylux.