Antti Koivisto
Senior Software Engineer at Apple
San Francisco, California, United States
Summary
🤩
Rockstar🎓
Top SchoolAntti Koivisto is a Senior Software Engineer with 26 years of experience specializing in WebKit and browser rendering technologies, currently working on iPhone software at Apple in San Francisco. He has deep expertise in CSS layout and rendering edge cases, having contributed significant fixes and performance improvements to WPE WebKit and authored conformance tests for Web Platform Tests (wpt) covering features like cascade layers, :has(), container queries and media queries. His background includes leading browser development at Nokia for the S60 platform, giving him a long view of mobile rendering constraints and interoperability challenges. Antti combines low-level engine work—text rendering, painting and layout—with front-end test automation to ensure spec-compliant behavior across browsers. He holds an MSc in Computer Science from the University of Helsinki and is known for pragmatic fixes that address subtle multi-line and pseudo-element rendering bugs that often evade conventional testing.
26 years of coding experience
8 years of employment as a software developer
MSc, Computer Science, MSc, Computer Science at University of Helsinki
Github Skills (17)
javascript10
c-language10
testing10
css10
webkit10
dom10
web-standards10
html10
rendering-engine10
layout-engine10
cprogramming-language10
test-automation10
webpagetest9
css-transitions9
css-selectors9
Programming languages (5)
Github contributions (5)
WebPlatformForEmbedded/WPEWebKit
Nov 2007 - Nov 2022
WPE WebKit port (downstream)
Role in this project:
Back-end Developer
Back-end DeveloperContributions:2340 commits in 15 years 2 months
Contributions summary:Antti primarily contributed to the WebKit WPE WebKit port, focusing on fixing and improving the rendering engine. Their work involved addressing issues with text rendering, particularly background-clip:text for inline boxes spanning multiple lines, improving CSS rule and text decoration implementations, and enhancing the processing of content in the layout. This involved modifications to the rendering engine and related layout components. The user also improved the handling of the container-queries implementation, handling the edge cases of display none and adding performance improvements.
wpedownstreamwebkit
web-platform-tests/wpt
Apr 2020 - Jan 2023
Test suites for Web platform specs — including WHATWG, W3C, and others
Role in this project:Front-end Developer & Test Automation Engineer
Front-end Developer & Test Automation EngineerContributions:13 reviews, 30 commits, 77 PRs in 2 years 9 months
Contributions summary:Antti primarily contributes to the web platform tests for the WPT repository. Their work involves creating and updating test cases for CSS features such as cascade layers, media queries, and the `:has()` selector, including tests for interactions with pseudo-classes, and custom properties. They also added and updated tests related to CSS container queries, and the CSS transition's starting-style. The user's contributions focus on ensuring browser implementations adhere to web standards.
microsoft-edgetest-runnerspecssafarifirefox
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