From 8b0e6ea46eb746df1b0c558ce906b3a8dd501c5e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Sun, 23 Apr 2017 11:21:39 +0200
Subject: [PATCH] style: Refactor overflow fixup to account for overflow: clip.

This is the missing piece to make the remaining contain tests not assert on
Gecko.
---
 .../style/properties/properties.mako.rs       | 54 +++++++++++++------
 1 file changed, 38 insertions(+), 16 deletions(-)

diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index 30ed8e3afc1..439829b8f25 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -2436,33 +2436,55 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
         use computed_values::overflow_x::T as overflow;
         use computed_values::overflow_y;
 
-        let overflow_x = style.get_box().clone_overflow_x();
-        let overflow_y = style.get_box().clone_overflow_y().0;
-        match (overflow_x == longhands::overflow_x::computed_value::T::visible,
-               overflow_y == longhands::overflow_x::computed_value::T::visible) {
-            (true, true) => {}
-            (true, _) => {
-                style.mutate_box().set_overflow_x(overflow::auto);
+        let original_overflow_x = style.get_box().clone_overflow_x();
+        let original_overflow_y = style.get_box().clone_overflow_y().0;
+        let mut overflow_x = original_overflow_x;
+        let mut overflow_y = original_overflow_y;
+
+        // CSS3 overflow-x and overflow-y require some fixup as well in some
+        // cases. overflow: clip and overflow: visible are meaningful only when
+        // used in both dimensions.
+        if overflow_x != overflow_y {
+            // If 'visible' is specified but doesn't match the other dimension,
+            // it turns into 'auto'.
+            if overflow_x == overflow::visible {
+                overflow_x = overflow::auto;
             }
-            (_, true) => {
-                style.mutate_box().set_overflow_y(overflow_y::T(overflow::auto));
+            if overflow_y == overflow::visible {
+                overflow_y = overflow::auto;
             }
-            _ => {}
+
+            % if product == "gecko":
+                // overflow: clip is deprecated, so convert to hidden if it's
+                // specified in only one dimension.
+                if overflow_x == overflow::clip {
+                    overflow_x = overflow::hidden;
+                }
+                if overflow_y == overflow::clip {
+                    overflow_y = overflow::hidden;
+                }
+            % endif
         }
 
         % if product == "gecko":
             use properties::longhands::contain;
             // When 'contain: paint', update overflow from 'visible' to 'clip'.
-            let contain = style.get_box().clone_contain();
-            if contain.contains(contain::PAINT) {
-                if let longhands::overflow_x::computed_value::T::visible = overflow_x {
-                    style.mutate_box().set_overflow_x(overflow::clip);
+            if style.get_box().clone_contain().contains(contain::PAINT) {
+                if overflow_x == overflow::visible {
+                    overflow_x = overflow::clip;
                 }
-                if let longhands::overflow_x::computed_value::T::visible = overflow_y {
-                    style.mutate_box().set_overflow_y(overflow_y::T(overflow::clip));
+                if overflow_y == overflow::visible {
+                    overflow_y = overflow::clip;
                 }
             }
         % endif
+
+        if overflow_x != original_overflow_x ||
+           overflow_y != original_overflow_y {
+            let mut box_style = style.mutate_box();
+            box_style.set_overflow_x(overflow_x);
+            box_style.set_overflow_y(overflow_y::T(overflow_y));
+        }
     }
 
     % if product == "gecko":