From f96c75c8d0aea0b6b04e87369cbfb5853b4ef89a Mon Sep 17 00:00:00 2001
From: Boris Chiou <boris.chiou@gmail.com>
Date: Thu, 4 May 2023 21:35:14 +0000
Subject: [PATCH] style: Update the syntax of scroll() to accept <scroller> and
 <axis> in any order

The order of <scroller> and <axis> doesn't matter in the parser.
However, we serialize <scroller> first, if it is not the initial value.

Differential Revision: https://phabricator.services.mozilla.com/D173906
---
 .../style/values/specified/animation.rs       | 28 ++++++++++++++-----
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/components/style/values/specified/animation.rs b/components/style/values/specified/animation.rs
index 767f5c54814..d832cd5aa63 100644
--- a/components/style/values/specified/animation.rs
+++ b/components/style/values/specified/animation.rs
@@ -283,12 +283,12 @@ impl Default for ScrollAxis {
 #[css(function = "scroll")]
 #[repr(C)]
 pub struct ScrollFunction {
-    /// The axis of scrolling that drives the progress of the timeline.
-    #[css(skip_if = "ScrollAxis::is_default")]
-    pub axis: ScrollAxis,
     /// The scroll container element whose scroll position drives the progress of the timeline.
     #[css(skip_if = "Scroller::is_default")]
     pub scroller: Scroller,
+    /// The axis of scrolling that drives the progress of the timeline.
+    #[css(skip_if = "ScrollAxis::is_default")]
+    pub axis: ScrollAxis,
 }
 
 impl ScrollFunction {
@@ -296,11 +296,25 @@ impl ScrollFunction {
     fn parse_arguments<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         // <scroll()> = scroll( [ <scroller> || <axis> ]? )
         // https://drafts.csswg.org/scroll-animations-1/#funcdef-scroll
-        //
-        // FIXME: This doesn't match the spec. I will update it in Bug 1814444.
+        let mut scroller = None;
+        let mut axis = None;
+        loop {
+            if scroller.is_none() {
+                scroller = input.try_parse(Scroller::parse).ok();
+            }
+
+            if axis.is_none() {
+                axis = input.try_parse(ScrollAxis::parse).ok();
+                if axis.is_some() {
+                    continue;
+                }
+            }
+            break;
+        }
+
         Ok(Self {
-            axis: input.try_parse(ScrollAxis::parse).unwrap_or_default(),
-            scroller: input.try_parse(Scroller::parse).unwrap_or_default(),
+            scroller: scroller.unwrap_or_default(),
+            axis: axis.unwrap_or_default(),
         })
     }
 }