| <!DOCTYPE html> |
| <link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#scroll-margin" /> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <style> |
| div { |
| position: absolute; |
| margin: 0px; |
| } |
| #scroller { |
| height: 500px; |
| width: 500px; |
| overflow: hidden; |
| scroll-snap-type: both mandatory; |
| } |
| #target { |
| width: 300px; |
| height: 300px; |
| background-color: blue; |
| } |
| #another-target { |
| width: 300px; |
| height: 300px; |
| top: 400px; |
| left: 400px; |
| background-color: blue; |
| scroll-snap-align: start; |
| } |
| </style> |
| |
| <div id="scroller"> |
| <div style="width: 2000px; height: 2000px;"></div> |
| <div id="target"></div> |
| <div id="another-target"></div> |
| </div> |
| |
| <script> |
| test(() => { |
| target.style.scrollSnapAlign = "start"; |
| target.style.scrollMargin = "100px"; |
| target.style.left = "300px"; |
| target.style.top = "300px"; |
| |
| scroller.scrollTo(0, 0); |
| // `target position (300px, 300px)` - `margin (100px, 100px)`. |
| assert_equals(scroller.scrollLeft, 200); |
| assert_equals(scroller.scrollTop, 200); |
| |
| target.style.scrollSnapAlign = "end"; |
| |
| // `target position (300px, 300px)` + `target size (300px, 300px) + |
| // `margin (100px, 100px) - `scroller size (500px, 500px)`. |
| scroller.scrollTo(0, 0); |
| assert_equals(scroller.scrollLeft, 200); |
| assert_equals(scroller.scrollTop, 200); |
| }, "Snaps to the positions adjusted by scroll-margin"); |
| |
| test(() => { |
| target.style.left = "0px"; |
| target.style.top = "0px"; |
| target.style.scrollSnapAlign = "start"; |
| |
| // Since the target is at (0px, 0px) in the scroll port, the added margin |
| // should not be considered, and the snap points for this snap area should be |
| // the closest points in the scroll port (i.e x=0 or y=0). |
| target.style.scrollMargin = "200px"; |
| |
| // Distance from target without margin: |
| // `scroll position (150px, 150px)` - `target position (0px, 0px)` |
| // = (150px, 150px) |
| // |
| // Distance from target with margin: |
| // `scroll position (150px, 150px)` - [`target position (0px, 0px)` - |
| // `target margin (200px, 200px)`] |
| // = (350px, 350px) |
| // |
| // Distance from other target: |
| // `other target position (400px, 400px)` - `scroll position (150px, 150px)` |
| // = (250px, 250px) |
| // |
| // Therefore if the "out-of-scrollport" scroll-margin contributes to the |
| // calculation, then the other target would be snapped to. However if the |
| // scroll-margin is not considered, then the (0px, 0px) target should be |
| // snapped to. |
| scroller.scrollTo(150, 150); |
| assert_equals(scroller.scrollLeft, 0); |
| assert_equals(scroller.scrollTop, 0); |
| }, "scroll-margin doesn't contribute to the snap position of the element " + |
| "if it's outside of the scroll port"); |
| </script> |
