| <!DOCTYPE html> |
| <html> |
| <meta charset="utf-8"> |
| <link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring-1/"> |
| <head> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <style type="text/css"> |
| #scroller { |
| overflow: scroll; |
| width: 500px; |
| height: 500px; |
| } |
| #anchor { |
| position: relative; |
| width: 100px; |
| height: 100px; |
| margin-top: 100px; |
| margin-bottom: 1000px; |
| background-color: blue; |
| } |
| #positioned { |
| position: absolute; |
| width: 10px; |
| height: 10px; |
| top: -200px; |
| background-color: yellow; |
| } |
| </style> |
| </head> |
| <body> |
| <div id="scroller"> |
| <div id="anchor"> |
| <div id="positioned"> |
| </div> |
| </div> |
| </div> |
| <script type="text/javascript"> |
| test(() => { |
| let scroller = document.querySelector('#scroller'); |
| let positioned = document.querySelector('#positioned'); |
| |
| // Scroll down to select #anchor as an anchor node |
| scroller.scrollTop = 20; |
| |
| // Move #positioned downwards, which will move the unclamped scrollable |
| // overflow rect of #anchor downards as well |
| positioned.style.top = '-180px'; |
| // To trigger the bug that this regression tests in Gecko, we need |
| // to not take Gecko's relative positioning fast path. To do |
| // this, change the 'left' of #positioned from 'auto' to '0px'. |
| positioned.style.left = '0px'; |
| |
| // The implementation should clamp the scrollable overflow rect |
| // before the start-edge of the anchor node, and not apply an |
| // adjustment |
| assert_equals(scroller.scrollTop, 20); |
| }, 'scrollable overflow before the start-edge of the anchor node should be clamped'); |
| </script> |
| </body> |
| </html> |