Factor scroll-margin values into scroll snap position calculation.

scroll-margin is for each elements in the scroll container and snap positions are shifted by the value. https://drafts.csswg.org/css-scroll-snap-1/#scroll-margin https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-area Differential Revision: https://phabricator.services.mozilla.com/D21634 bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1373833 gecko-commit: acbcbc1dc6e0d261a41620e0ee5ad0e73edc15ac gecko-integration-branch: central gecko-reviewers: botond
web-platform-tests · May 16, 2019 · 2e292e7 · 2e292e7
1 parent 3d80ec3
commit 2e292e7
Showing 1 changed file with 73 additions and 0 deletions.
diff --git a/css/css-scroll-snap/scroll-margin.html b/css/css-scroll-snap/scroll-margin.html
@@ -0,0 +1,73 @@
+<!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";
+ target.style.scrollMargin = "100px";
+
+ // Scroll to the position between #target and #another-target elements but
+ // if the scroll-margin 100px contributed to the snap start-aligned snap
+ // position it will be farther than #another-target.
+ scroller.scrollTo(200, 200);
+ 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>