The slabtype algorithm, Part 3: Iterative line splitting

Algorithms, Flash, Graphic Design, Interactive Design, Typography,
1/28/08

This is the third in a four-part graphical dissection of the “slabtype” text layout algorithm I developed for Public Secrets. For an introduction to the algorithm, visit The slabtype algorithm, Part 1: Background. To review the calculations that set the stage for this post, visit Part 2: Initial calculations.

In this post, we’ll take up the real workhorse of the slabtype algorithm—iterative line splitting—followed by the final layout of the text.

Our initial calculations provided us with a single very important number: 8, our ideal character count per line. This number gives us a target to aim for as we split our text into individual lines. We start by dividing our text into its constituent words:

Next, we execute the following iterative sequence:

1. Create two containers for words. One will hold the next word of the text, the other will hold the next two words of the text.
2. Keep adding subsequent words to both containers until the character length of one container is less than or equal to the length of the ideal character count per line, while the character length of the other container is greater than the ideal character count per line.
3. Store the contents of the container whose character count is closest to the ideal character count per line.
4. Repeat.

Here’s a diagram of how we arrive at our first line using this sequence:

In this example, our two word containers initially hold the words “I and “I WISH. Neither of these exceed the ideal character count per line, so we continue adding words, giving us “I WISH and “I WISH IT. The latter is ten characters long, two characters longer than our ideal character count per line of eight. Since the former is seven characters long, resulting in only a one-character difference between its length and the ideal, we store “I WISH as the contents as the first line of the slab.

Here’s how we arrive at the next line:

Here, we have a very similar case. Neither IT nor IT WAS exceed the ideal character count, so we proceed to IT WAS and IT WAS THAT. IT WAS is only two characters off the ideal, compared to three characters for IT WAS THAT, so we pick the former.

The third line plays out a bit differently.  With THAT and THAT SIMPLE, we find that THAT SIMPLE’s character count of eleven is nearer the target of eight than THAT’s character count of four, so we go with the latter.

The fourth line plays out much like the first two:

While the fifth pass chooses the first of the two text containers:

The sixth finds ERASE MY matching the ideal character count per line exactly:

Leaving PAST” as our only remaining word, which becomes a line unto itself.

Since we have exhausted our available words, the iterative part of the algorithm ends, resulting in our original text being split into seven lines:

For the final installment, we’ll turn our attention to laying out the text within the target box (source code will be provided).

Coming soon: The slabtype algorithm, Part 4: Final layout and source code