Figuring out viewport differences in between Gecko, Blink and WebKit

Viewport

We had a couple of Web Compatibility issues on the rendering of some sites related to the viewport information. Here after is a preliminary test for trying to figure out what are the sources of variability.

The major visible difference is only for the last case where Firefox and Chrome do something different.

• m.gd.ru with a hard coded viewport of 450px.
• www.tnm.jp with a hard coded viewport of 450px.
• ead.cesumar.br with a initial-scale=0

I haven't tested all combinations yet. Just a couple to have an idea. This is preliminary work to figure out the Web Compatibility space.

Maybe I can adjust tests in the future.

case A and case F below seems to highlight differences in between Gecko and Blink. Chrome seems to apply different logic for resizing the content.

Device parameters for the test

Using this page instrospection tool

Safari 9.0 OS 9.3.5

window.innerWidth = 320
window.outerWidth = 0
window.screen.width = 320
document.documentElement.clientWidth = 320
window.devicePixelRatio = 2

Firefox Nightly 51

window.innerWidth = 360
window.outerWidth = 360
window.screen.width = 360
document.documentElement.clientWidth = 360
window.devicePixelRatio = 3

Chrome/Opera 52

window.innerWidth = 360
window.outerWidth = 360
window.screen.width = 360
document.documentElement.clientWidth = 360
window.devicePixelRatio = 3

Results for different viewport content adaptation

Case A. width=250px with larger paragraph

Case B. width=250px with no paragraph size

Case C. width=550px with larger paragraph

Case D. width=450px with no paragraph size

Case E. not scalable with larger paragraph

Case F. scalable with larger paragraph

Otsukare!