Software Design by Example in Python 14: Page Layout

As I said a week ago, some people think you don’t really understand how computers work unless you’ve written a compiler. My rejoinder these days is that writing a web browser will teach you a lot more about modern computer systems. Panchekha and Harrelson’s Web Browser Engineering covers everything from downloading HTML and constructing a DOM tree to keeping data private, scheduling tasks, caching, and accessibility. I couldn’t possibly cover all of that, so Chapter 14: Page Layout focused on one small problem: how to decide what is displayed where on a page.

That question led to the most intensely algorithmic chapter of the book, as row-and-column layout with elastic constraints requires a bit of tricksy recursion. The chapter doesn’t get very far, but I hope that by the end readers will understand that the problem is much harder than it first appears and that CSS is every bit as much a programming language as Lisp or C++.

Terms defined: accidental complexity, block (on page), confirmation bias, easy mode, intrinsic complexity, layout engine, Liskov Substitution Principle, mixin class, z-buffering.