Fix some writing mode mismatch assertions errors.

The rendering is still wrong beause of #2795, but at least we get a rendering. (This test change is just for readability, it should be equivalent to before.)
servo · SimonSapin · Dec 18, 2014 · Dec 18, 2014 · 7be30dee8e480dc1e965fe693061a795749d7786
commit 7be30dee8e480dc1e965fe693061a795749d7786
diff --git a/components/layout/block.rs b/components/layout/block.rs
@@ -1783,9 +1783,9 @@ impl Flow for BlockFlow {
             if !flow::base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
                 let kid_base = flow::mut_base(kid);
                 kid_base.stacking_relative_position =
-                    origin_for_children +
-                    (kid_base.position.start + relative_offset).to_physical(writing_mode,
-                                                                            container_size);
+                    origin_for_children
+                    + kid_base.position.start.to_physical(kid_base.writing_mode, container_size)
+                    + relative_offset.to_physical(writing_mode);
             }
 
             flow::mut_base(kid).absolute_position_info = absolute_position_info_for_children;

diff --git a/components/layout/flow.rs b/components/layout/flow.rs
@@ -1191,20 +1191,27 @@ impl<'a> MutableFlowUtils for &'a mut Flow + 'a {
         let mut overflow = my_position;
 
         if self.is_block_container() {
+            let writing_mode = base(self).writing_mode;
+            // FIXME(#2795): Get the real container size
+            let container_size = Size2D::zero();
             for kid in child_iter(self) {
                 if kid.is_store_overflow_delayed() {
                     // Absolute flows will be handled by their CB. If we are
                     // their CB, they will show up in `abs_descendants`.
                     continue;
                 }
-                let mut kid_overflow = base(kid).overflow;
+                let kid_base = base(kid);
+                let mut kid_overflow = kid_base.overflow.convert(
+                    kid_base.writing_mode, writing_mode, container_size);
                 kid_overflow = kid_overflow.translate(&my_position.start);
                 overflow = overflow.union(&kid_overflow)
             }
 
             // FIXME(#2004, pcwalton): This is wrong for `position: fixed`.
             for descendant_link in mut_base(self).abs_descendants.iter() {
-                let mut kid_overflow = base(descendant_link).overflow;
+                let kid_base = base(descendant_link);
+                let mut kid_overflow = kid_base.overflow.convert(
+                    kid_base.writing_mode, writing_mode, container_size);
                 kid_overflow = kid_overflow.translate(&my_position.start);
                 overflow = overflow.union(&kid_overflow)
             }

diff --git a/tests/ref/overconstrained_block.html b/tests/ref/overconstrained_block.html
@@ -2,14 +2,17 @@
   <head>
     <title>Block with over-contrained margins+borders+padding+width = containing block width</title>
     <style>
-      body { width: 300px; margin: 0 }
-      p { background: green; width: 200px; height: 100px; margin: 20px 70px }
+      body { width: 300px; margin: 0 0 0 400px }
+      div:nth-child(even) { direction: rtl }
+      div:nth-child(1) p, div:nth-child(2) p { margin: 20px 70px }
+      div:nth-child(3) p, div:nth-child(4) p { margin: 20px 120px }
+      p { background: green; width: 200px; height: 100px }
     </style>
   </head>
   <body>
-    <p style="margin: 20px 70px"></p>
-    <p style="margin: 20px 70px; direction: rtl"></p>
-    <p style="margin: 20px 120px"></p>
-    <p style="margin: 20px 120px; direction: rtl"></p>
+    <div><p></p></div>
+    <div><p></p></div>
+    <div><p></p></div>
+    <div><p></p></div>
   </body>
 </html>