paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

domenic

The scenario:

• We are writing a digital textbook-reading app.
• Most of the time you have a "basic" license for your textbook, but one (and only one) of your computers can request an "enhanced" license.
• You can only print from the computer with the enhanced license.

The problem statement: