canvas.context.measureText returns '0'

[rsimonton]

Description

Creating a dynamic canvas element and attempting to use its 2d context to measure text always renders a width of '0'.

Steps to Reproduce

https://jsfiddle.net/jdmtu2xL/

Actual result:

Width of test string "Testing...1..2...3...." is: 0 :(

Expected result:

Width of test string "Testing...1..2...3...." is: 114.392578125 :)

Reproduces how often:

Consistently

Brave version (brave://version info)

Brave: 0.55.18 Chromium: 70.0.3538.67 (Official Build) (64-bit)
Revision: 9ab0cfab84ded083718d3a4ff830726efd38869f-refs/branch-heads/3538@{#1002}
OS: Mac OS X

Website problems only:

• Does the issue resolve itself when disabling Brave Shields? no
• Is the issue reproducible on the latest version of Chrome? no

Thanks for Brave!

[srirambv]

The Canvas Fingerprinting is blocked. Hence you see Width of test string "Testing...1..2...3...." is: 0 :(. Try setting Fingerprint protection to Allow All fingerprinting in Shields(lion icon in URL bar) and you will see the desired result. This is expected with blocking fingerprint mechanism

[subzey]

Can't the measurement result just be of lower precision, not always 0?

As for me, zeroing 44 out of the 53 bits of the Double mantissa would do. That would significantly complicate the fignerprinting while keeping all this stuff in the working condition.

Demo

Also, currently the feature can identify user as scripts now knows for sure that Brave is used 😁

[bsclifton]

cc: @diracdeltas @riastradh-brave about the above comment RE: fingerprinting