Bug 1900231: Parse anchor-center for self-alignment properties. r=firefox-style-system-reviewers,emilio

Differential Revision: https://phabricator.services.mozilla.com/D221872

layout/generic/CSSAlignUtils.cpp

@@ -116,7 +116,9 @@ nscoord CSSAlignUtils::AlignJustifySelf(const StyleAlignFlags& aAlignment,
   } else if (alignment == StyleAlignFlags::END) {
     nscoord size = aChildSize.Size(aAxis, wm);
     offset = aCBSize - (size + marginEnd);
-  } else if (alignment == StyleAlignFlags::CENTER) {
+  } else if (alignment == StyleAlignFlags::CENTER ||
+             alignment == StyleAlignFlags::ANCHOR_CENTER) {
+    // TODO(dshin, Bug 1909339): For now, treat `anchor-center` as `center`.
     nscoord size = aChildSize.Size(aAxis, wm);
     offset = (aCBSize - size + marginStart - marginEnd) / 2;
   } else {

layout/generic/nsFlexContainerFrame.cpp

@@ -3992,7 +3992,9 @@ void SingleLineCrossAxisPositionTracker::EnterAlignPackingSpace(
     // No space to skip over -- we're done.
   } else if (alignSelf == StyleAlignFlags::FLEX_END) {
     mPosition += aLine.LineCrossSize() - aItem.OuterCrossSize();
-  } else if (alignSelf == StyleAlignFlags::CENTER) {
+  } else if (alignSelf == StyleAlignFlags::CENTER ||
+             alignSelf == StyleAlignFlags::ANCHOR_CENTER) {
+    // TODO(dshin, Bug 1909339): For now, treat `anchor-center` as `center`.
     // Note: If cross-size is odd, the "after" space will get the extra unit.
     mPosition += (aLine.LineCrossSize() - aItem.OuterCrossSize()) / 2;
   } else if (alignSelf == StyleAlignFlags::BASELINE ||

servo/components/style/values/specified/align.rs

@@ -55,6 +55,8 @@ bitflags! {
         const SPACE_AROUND = 15;
         /// 'space-evenly'
         const SPACE_EVENLY = 16;
+        /// `anchor-center`
+        const ANCHOR_CENTER = 17;
 
         // Additional flags stored in the upper bits:
         /// 'legacy' (mutually exclusive w. SAFE & UNSAFE)
@@ -124,6 +126,7 @@ impl ToCss for AlignFlags {
             AlignFlags::SPACE_BETWEEN => "space-between",
             AlignFlags::SPACE_AROUND => "space-around",
             AlignFlags::SPACE_EVENLY => "space-evenly",
+            AlignFlags::ANCHOR_CENTER => "anchor-center",
             _ => unreachable!(),
         })
     }
@@ -718,6 +721,7 @@ fn parse_self_position<'i, 't>(
         "self-end" => AlignFlags::SELF_END,
         "left" if axis == AxisDirection::Inline => AlignFlags::LEFT,
         "right" if axis == AxisDirection::Inline => AlignFlags::RIGHT,
+        "anchor-center" if static_prefs::pref!("layout.css.anchor-positioning.enabled") => AlignFlags::ANCHOR_CENTER,
     })
 }
 
@@ -730,6 +734,7 @@ fn list_self_position_keywords(f: KeywordsCollectFn, axis: AxisDirection) {
         "center",
         "self-start",
         "self-end",
+        "anchor-center",
     ]);
     if axis == AxisDirection::Inline {
         f(&["left", "right"]);

testing/web-platform/meta/css/css-anchor-position/anchor-center-001.html.ini

@@ -1,24 +0,0 @@
-[anchor-center-001.html]
-  [e.style['align-self'\] = "anchor-center" should set the property value]
-    expected: FAIL
-
-  [e.style['align-items'\] = "anchor-center" should set the property value]
-    expected: FAIL
-
-  [e.style['justify-self'\] = "anchor-center" should set the property value]
-    expected: FAIL
-
-  [e.style['justify-items'\] = "anchor-center" should set the property value]
-    expected: FAIL
-
-  [Property align-self value 'anchor-center']
-    expected: FAIL
-
-  [Property align-items value 'anchor-center']
-    expected: FAIL
-
-  [Property justify-self value 'anchor-center']
-    expected: FAIL
-
-  [Property justify-items value 'anchor-center']
-    expected: FAIL

testing/web-platform/meta/css/css-anchor-position/anchor-center-002.html.ini

@@ -1,2 +0,0 @@
-[anchor-center-002.html]
-  expected: FAIL