Merge pull request #3110 from SimonSapin/writing-modes-reftest

Add a basic CSS Writing Modes reftest

13 files changed, 553 insertions, 85 deletions

diff --git a/src/components/gfx/display_list/mod.rs b/src/components/gfx/display_list/mod.rs
index 21c8c8a25b5..0ad7d945ae1 100644
--- a/src/components/gfx/display_list/mod.rs
+++ b/src/components/gfx/display_list/mod.rs
@@ -316,7 +316,6 @@ impl DisplayList {
         }
     }
 
-
     /// Appends the given item to the display list.
     pub fn push(&mut self, item: DisplayItem) {
         self.list.push(item)
@@ -328,6 +327,14 @@ impl DisplayList {
         self.list.append(other.list)
     }
 
+    pub fn debug(&self) {
+        if log_enabled!(::log::DEBUG) {
+            for item in self.list.iter() {
+                item.debug_with_level(0);
+            }
+        }
+    }
+
     /// Draws the display list into the given render context. The display list must be flattened
     /// first for correct painting.
     pub fn draw_into_context(&self, render_context: &mut RenderContext) {
@@ -724,14 +731,14 @@ impl DisplayItem {
     }
 
     pub fn debug_with_level(&self, level: uint) {
-            let mut indent = String::new();
-            for _ in range(0, level) {
-                indent.push_str("| ")
-            }
-            debug!("{}+ {}", indent, self);
-            for child in self.children() {
-                child.debug_with_level(level + 1);
-            }
+        let mut indent = String::new();
+        for _ in range(0, level) {
+            indent.push_str("| ")
+        }
+        debug!("{}+ {}", indent, self);
+        for child in self.children() {
+            child.debug_with_level(level + 1);
+        }
     }
 }
 
diff --git a/src/components/layout/block.rs b/src/components/layout/block.rs
index ea65756c7de..4c17cebc97f 100644
--- a/src/components/layout/block.rs
+++ b/src/components/layout/block.rs
@@ -1110,16 +1110,18 @@ impl BlockFlow {
                                              .relative_containing_block_size,
                                         None);
 
+        // FIXME(#2795): Get the real container size
+        let container_size = Size2D::zero();
+
         // Add the box that starts the block context.
         let mut display_list = DisplayList::new();
-        let mut accumulator =
-            self.fragment.build_display_list(&mut display_list,
-                                             layout_context,
-                                             self.base.abs_position
-                                                .add_point(&offset)
-                                                + rel_offset,
-                                             background_border_level,
-                                             None);
+        let mut accumulator = self.fragment.build_display_list(
+            &mut display_list,
+            layout_context,
+            self.base.abs_position + (offset + rel_offset).to_physical(
+                self.base.writing_mode, container_size),
+            background_border_level,
+            None);
 
         let mut child_layers = DList::new();
         for kid in self.base.child_iter() {
@@ -1592,17 +1594,22 @@ impl Flow for BlockFlow {
     }
 
     fn compute_absolute_position(&mut self) {
+        // FIXME(#2795): Get the real container size
+        let container_size = Size2D::zero();
+
         if self.is_absolutely_positioned() {
+            let position_start = self.base.position.start.to_physical(
+                self.base.writing_mode, container_size);
             self.base
                 .absolute_position_info
                 .absolute_containing_block_position = if self.is_fixed() {
                 // The viewport is initially at (0, 0).
-                self.base.position.start
+                position_start
             } else {
                 // Absolute position of the containing block + position of absolute flow w/r/t the
                 // containing block.
                 self.base.absolute_position_info.absolute_containing_block_position
-                    .add_point(&self.base.position.start)
+                    + position_start
             };
 
             // Set the absolute position, which will be passed down later as part
@@ -1622,8 +1629,8 @@ impl Flow for BlockFlow {
         if self.is_positioned() {
             self.base.absolute_position_info.absolute_containing_block_position =
                 self.base.abs_position
-                .add_point(&self.generated_containing_block_rect().start)
-                + relative_offset
+                + (self.generated_containing_block_rect().start
+                   + relative_offset).to_physical(self.base.writing_mode, container_size)
         }
 
         let float_offset = if self.is_float() {
@@ -1640,14 +1647,14 @@ impl Flow for BlockFlow {
 
         // Process children.
         let this_position = self.base.abs_position;
+        let writing_mode = self.base.writing_mode;
         for kid in self.base.child_iter() {
             if !kid.is_absolutely_positioned() {
                 let kid_base = flow::mut_base(kid);
-                kid_base.abs_position =
-                    this_position
-                    .add_point(&kid_base.position.start)
+                kid_base.abs_position = this_position + (
+                    kid_base.position.start
                     .add_point(&float_offset)
-                    + relative_offset;
+                    + relative_offset).to_physical(writing_mode, container_size);
                 kid_base.absolute_position_info = absolute_position_info
             }
         }
diff --git a/src/components/layout/flow.rs b/src/components/layout/flow.rs
index e401a1f75c6..27091eb7665 100644
--- a/src/components/layout/flow.rs
+++ b/src/components/layout/flow.rs
@@ -46,13 +46,15 @@ use table_cell::TableCellFlow;
 use wrapper::ThreadSafeLayoutNode;
 
 use collections::dlist::DList;
+use geom::Point2D;
 use gfx::display_list::DisplayList;
 use gfx::render_task::RenderLayer;
 use servo_msg::compositor_msg::LayerId;
 use servo_util::geometry::Au;
 use servo_util::logical_geometry::WritingMode;
-use servo_util::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize};
+use servo_util::logical_geometry::{LogicalRect, LogicalSize};
 use std::mem;
+use std::num::Zero;
 use std::fmt;
 use std::iter::Zip;
 use std::sync::atomics::{AtomicUint, Relaxed, SeqCst};
@@ -596,7 +598,7 @@ pub struct AbsolutePositionInfo {
     /// The size of the containing block for relatively-positioned descendants.
     pub relative_containing_block_size: LogicalSize<Au>,
     /// The position of the absolute containing block.
-    pub absolute_containing_block_position: LogicalPoint<Au>,
+    pub absolute_containing_block_position: Point2D<Au>,
     /// Whether the absolute containing block forces positioned descendants to be layerized.
     ///
     /// FIXME(pcwalton): Move into `FlowFlags`.
@@ -609,7 +611,7 @@ impl AbsolutePositionInfo {
         // of the root layer.
         AbsolutePositionInfo {
             relative_containing_block_size: LogicalSize::zero(writing_mode),
-            absolute_containing_block_position: LogicalPoint::zero(writing_mode),
+            absolute_containing_block_position: Zero::zero(),
             layers_needed_for_positioned_flows: false,
         }
     }
@@ -660,7 +662,7 @@ pub struct BaseFlow {
     pub collapsible_margins: CollapsibleMargins,
 
     /// The position of this flow in page coordinates, computed during display list construction.
-    pub abs_position: LogicalPoint<Au>,
+    pub abs_position: Point2D<Au>,
 
     /// Details about descendants with position 'absolute' or 'fixed' for which we are the
     /// containing block. This is in tree order. This includes any direct children.
@@ -724,7 +726,7 @@ impl BaseFlow {
 
             floats: Floats::new(writing_mode),
             collapsible_margins: CollapsibleMargins::new(),
-            abs_position: LogicalPoint::zero(writing_mode),
+            abs_position: Zero::zero(),
             abs_descendants: Descendants::new(),
             absolute_static_i_offset: Au::new(0),
             fixed_static_i_offset: Au::new(0),
diff --git a/src/components/layout/fragment.rs b/src/components/layout/fragment.rs
index 7f61517a328..316f29c0d23 100644
--- a/src/components/layout/fragment.rs
+++ b/src/components/layout/fragment.rs
@@ -37,7 +37,7 @@ use servo_net::image::holder::ImageHolder;
 use servo_net::local_image_cache::LocalImageCache;
 use servo_util::geometry::Au;
 use servo_util::geometry;
-use servo_util::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize, LogicalMargin};
+use servo_util::logical_geometry::{LogicalRect, LogicalSize, LogicalMargin};
 use servo_util::range::*;
 use servo_util::namespace;
 use servo_util::smallvec::SmallVec;
@@ -776,15 +776,15 @@ impl Fragment {
 
     fn build_debug_borders_around_text_fragments(&self,
                                              display_list: &mut DisplayList,
-                                             flow_origin: LogicalPoint<Au>,
+                                             flow_origin: Point2D<Au>,
                                              text_fragment: &ScannedTextFragmentInfo) {
-        let mut fragment_bounds = self.border_box.clone();
-        fragment_bounds.start.i = fragment_bounds.start.i + flow_origin.i;
-        fragment_bounds.start.b = fragment_bounds.start.b + flow_origin.b;
         // FIXME(#2795): Get the real container size
         let container_size = Size2D::zero();
-        let absolute_fragment_bounds = fragment_bounds.to_physical(
-            self.style.writing_mode, container_size);
+        // Fragment position wrt to the owning flow.
+        let fragment_bounds = self.border_box.to_physical(self.style.writing_mode, container_size);
+        let absolute_fragment_bounds = Rect(
+            fragment_bounds.origin + flow_origin,
+            fragment_bounds.size);
 
         // Compute the text fragment bounds and draw a border surrounding them.
         let border_display_item = box BorderDisplayItem {
@@ -797,13 +797,11 @@ impl Fragment {
 
         // Draw a rectangle representing the baselines.
         let ascent = text_fragment.run.ascent();
-        let baseline = LogicalRect::new(
-            self.style.writing_mode,
-            fragment_bounds.start.i,
-            fragment_bounds.start.b + ascent,
-            fragment_bounds.size.inline,
-            Au(0)
-        ).to_physical(self.style.writing_mode, container_size);
+        let mut baseline = self.border_box.clone();
+        baseline.start.b = baseline.start.b + ascent;
+        baseline.size.block = Au(0);
+        let mut baseline = baseline.to_physical(self.style.writing_mode, container_size);
+        baseline.origin = baseline.origin + flow_origin;
 
         let line_display_item = box LineDisplayItem {
             base: BaseDisplayItem::new(baseline, self.node, ContentStackingLevel),
@@ -815,14 +813,14 @@ impl Fragment {
 
     fn build_debug_borders_around_fragment(&self,
                                       display_list: &mut DisplayList,
-                                      flow_origin: LogicalPoint<Au>) {
-        let mut fragment_bounds = self.border_box.clone();
-        fragment_bounds.start.i = fragment_bounds.start.i + flow_origin.i;
-        fragment_bounds.start.b = fragment_bounds.start.b + flow_origin.b;
+                                      flow_origin: Point2D<Au>) {
         // FIXME(#2795): Get the real container size
         let container_size = Size2D::zero();
-        let absolute_fragment_bounds = fragment_bounds.to_physical(
-            self.style.writing_mode, container_size);
+        // Fragment position wrt to the owning flow.
+        let fragment_bounds = self.border_box.to_physical(self.style.writing_mode, container_size);
+        let absolute_fragment_bounds = Rect(
+            fragment_bounds.origin + flow_origin,
+            fragment_bounds.size);
 
         // This prints a debug border around the border of this fragment.
         let border_display_item = box BorderDisplayItem {
@@ -845,18 +843,17 @@ impl Fragment {
     pub fn build_display_list(&self,
                               display_list: &mut DisplayList,
                               layout_context: &LayoutContext,
-                              flow_origin: LogicalPoint<Au>,
+                              flow_origin: Point2D<Au>,
                               background_and_border_level: BackgroundAndBorderLevel,
                               inline_fragment_context: Option<InlineFragmentContext>)
                               -> ChildDisplayListAccumulator {
-        // Fragment position wrt to the owning flow.
-        let mut fragment_bounds = self.border_box.clone();
-        fragment_bounds.start.i = fragment_bounds.start.i + flow_origin.i;
-        fragment_bounds.start.b = fragment_bounds.start.b + flow_origin.b;
         // FIXME(#2795): Get the real container size
         let container_size = Size2D::zero();
-        let absolute_fragment_bounds = fragment_bounds.to_physical(
-            self.style.writing_mode, container_size);
+        // Fragment position wrt to the owning flow.
+        let fragment_bounds = self.border_box.to_physical(self.style.writing_mode, container_size);
+        let absolute_fragment_bounds = Rect(
+            fragment_bounds.origin + flow_origin,
+            fragment_bounds.size);
         debug!("Fragment::build_display_list at rel={}, abs={}: {}",
                self.border_box,
                absolute_fragment_bounds,
@@ -1413,21 +1410,18 @@ impl Fragment {
     #[inline(never)]
     fn finalize_position_and_size_of_iframe(&self,
                                             iframe_fragment: &IframeFragmentInfo,
-                                            offset: LogicalPoint<Au>,
+                                            offset: Point2D<Au>,
                                             layout_context: &LayoutContext) {
-        let inline_start = offset.i + self.margin.inline_start + self.border_padding.inline_start;
-        let block_start = offset.b + self.margin.block_start + self.border_padding.block_start;
-        let inline_size = self.content_box().size.inline;
-        let block_size = self.content_box().size.block;
-        // FIXME(#2795): Get the real container size
-        let container_size = Size2D::zero();
-        let rect = LogicalRect::new(
-            self.style.writing_mode,
-            geometry::to_frac_px(inline_start) as f32,
-            geometry::to_frac_px(block_start) as f32,
-            geometry::to_frac_px(inline_size) as f32,
-            geometry::to_frac_px(block_size) as f32
-        ).to_physical(self.style.writing_mode, container_size);
+        let mbp = (self.margin + self.border_padding).to_physical(self.style.writing_mode);
+        let content_size = self.content_box().size.to_physical(self.style.writing_mode);
+
+        let left = offset.x + mbp.left;
+        let top = offset.y + mbp.top;
+        let width = content_size.width;
+        let height = content_size.height;
+        let origin = Point2D(geometry::to_frac_px(left) as f32, geometry::to_frac_px(top) as f32);
+        let size = Size2D(geometry::to_frac_px(width) as f32, geometry::to_frac_px(height) as f32);
+        let rect = Rect(origin, size);
 
         debug!("finalizing position and size of iframe for {:?},{:?}",
                iframe_fragment.pipeline_id,
diff --git a/src/components/layout/inline.rs b/src/components/layout/inline.rs
index 1a427f79c0b..9b6b0af28d7 100644
--- a/src/components/layout/inline.rs
+++ b/src/components/layout/inline.rs
@@ -16,7 +16,7 @@ use text;
 use wrapper::ThreadSafeLayoutNode;
 
 use collections::{Deque, RingBuf};
-use geom::Size2D;
+use geom::Rect;
 use gfx::display_list::ContentLevel;
 use gfx::font::FontMetrics;
 use gfx::font_context::FontContext;
@@ -927,12 +927,8 @@ impl InlineFlow {
     }
 
     pub fn build_display_list_inline(&mut self, layout_context: &LayoutContext) {
-        let abs_rect = LogicalRect::from_point_size(
-            self.base.writing_mode, self.base.abs_position, self.base.position.size);
-        // FIXME(#2795): Get the real container size
-        let container_size = Size2D::zero();
-        if !abs_rect.to_physical(self.base.writing_mode, container_size)
-                    .intersects(&layout_context.shared.dirty) {
+        let size = self.base.position.size.to_physical(self.base.writing_mode);
+        if !Rect(self.base.abs_position, size).intersects(&layout_context.shared.dirty) {
             return
         }
 
@@ -947,7 +943,8 @@ impl InlineFlow {
                                                         Some(context));
             drop(fragment.build_display_list(&mut self.base.display_list,
                                              layout_context,
-                                             self.base.abs_position + rel_offset,
+                                             self.base.abs_position.add_size(
+                                                &rel_offset.to_physical(self.base.writing_mode)),
                                              ContentLevel,
                                              Some(context)));
         }
diff --git a/src/components/layout/layout_task.rs b/src/components/layout/layout_task.rs
index e4cba397379..e104ea443fe 100644
--- a/src/components/layout/layout_task.rs
+++ b/src/components/layout/layout_task.rs
@@ -46,6 +46,7 @@ use gfx::font_cache_task::{FontCacheTask};
 use servo_net::local_image_cache::{ImageResponder, LocalImageCache};
 use servo_util::geometry::Au;
 use servo_util::geometry;
+use servo_util::logical_geometry::LogicalPoint;
 use servo_util::opts::Opts;
 use servo_util::smallvec::{SmallVec, SmallVec1};
 use servo_util::time::{TimeProfilerChan, profile};
@@ -694,10 +695,10 @@ impl LayoutTask {
         if data.goal == ReflowForDisplay {
             let writing_mode = flow::base(layout_root.get()).writing_mode;
             profile(time::LayoutDispListBuildCategory, self.time_profiler_chan.clone(), || {
-                // FIXME(#2795): Get the real container size
-                let container_size = Size2D::zero();
                 shared_layout_ctx.dirty = flow::base(layout_root.get()).position.to_physical(
-                    writing_mode, container_size);
+                    writing_mode, self.screen_size);
+                flow::mut_base(layout_root.get_mut()).abs_position =
+                    LogicalPoint::zero(writing_mode).to_physical(writing_mode, self.screen_size);
 
                 match self.parallel_traversal {
                     None => {
@@ -718,6 +719,7 @@ impl LayoutTask {
                 let root_display_list =
                     mem::replace(&mut flow::mut_base(layout_root.get_mut()).display_list,
                                  DisplayList::new());
+                root_display_list.debug();
                 let display_list = Arc::new(root_display_list.flatten(ContentStackingLevel));
 
                 // FIXME(pcwalton): This is really ugly and can't handle overflow: scroll. Refactor
diff --git a/src/components/util/geometry.rs b/src/components/util/geometry.rs
index 70882f17178..2b1082fa3d2 100644
--- a/src/components/util/geometry.rs
+++ b/src/components/util/geometry.rs
@@ -79,8 +79,7 @@ impl Default for Au {
 
 impl fmt::Show for Au {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let Au(n) = *self;
-        write!(f, "Au(au={} px={})", n, to_frac_px(*self))
+        write!(f, "{}px", to_frac_px(*self))
     }}
 
 impl Add<Au,Au> for Au {
diff --git a/src/support/geom/rust-geom b/src/support/geom/rust-geom
-Subproject b41f144a3a8b6388d0956f341bcffa5bbaecc89
+Subproject c733f78e06bd02f7498e93b391e0f6094d91786
diff --git a/src/test/harness/reftest/reftest.rs b/src/test/harness/reftest/reftest.rs
index f0ec11ddc98..57738bbf517 100644
--- a/src/test/harness/reftest/reftest.rs
+++ b/src/test/harness/reftest/reftest.rs
@@ -114,6 +114,7 @@ struct Reftest {
     servo_args: Vec<String>,
     render_mode: RenderMode,
     is_flaky: bool,
+    experimental: bool,
 }
 
 struct TestLine<'a> {
@@ -166,12 +167,14 @@ fn parse_lists(file: &str, servo_args: &[String], render_mode: RenderMode, id_of
 
         let mut conditions_list = test_line.conditions.split(',');
         let mut flakiness = RenderMode::empty();
+        let mut experimental = false;
         for condition in conditions_list {
             match condition {
                 "flaky_cpu" => flakiness.insert(CpuRendering),
                 "flaky_gpu" => flakiness.insert(GpuRendering),
                 "flaky_linux" => flakiness.insert(LinuxTarget),
                 "flaky_macos" => flakiness.insert(MacOsTarget),
+                "experimental" => experimental = true,
                 _ => (),
             }
         }
@@ -184,6 +187,7 @@ fn parse_lists(file: &str, servo_args: &[String], render_mode: RenderMode, id_of
             render_mode: render_mode,
             servo_args: servo_args.iter().map(|x| x.clone()).collect(),
             is_flaky: render_mode.intersects(flakiness),
+            experimental: experimental,
         };
 
         tests.push(make_test(reftest));
@@ -212,7 +216,11 @@ fn capture(reftest: &Reftest, side: uint) -> png::Image {
     if reftest.render_mode.contains(CpuRendering) {
         args.push("-c".to_string());
     }
-    args.push_all_move(vec!("-f".to_string(), "-o".to_string(), filename.clone(), reftest.files[side].clone()));
+    if reftest.experimental {
+        args.push("--experimental".to_string());
+    }
+    args.push_all(["-f".to_string(), "-o".to_string(), filename.clone(),
+                   reftest.files[side].clone()]);
 
     let retval = match Command::new("./servo").args(args.as_slice()).status() {
         Ok(status) => status,
diff --git a/src/test/harness/reftest/reftest.rs.orig b/src/test/harness/reftest/reftest.rs.orig
new file mode 100644
index 00000000000..645a8d55307
--- /dev/null
+++ b/src/test/harness/reftest/reftest.rs.orig
@@ -0,0 +1,415 @@
+// Copyright 2013 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern crate png;
+extern crate std;
+extern crate test;
+extern crate regex;
+
+use std::ascii::StrAsciiExt;
+use std::io;
+use std::io::{File, Reader, Command};
+use std::io::process::ExitStatus;
+use std::os;
+use test::{AutoColor, DynTestName, DynTestFn, TestDesc, TestOpts, TestDescAndFn};
+use test::run_tests_console;
+use regex::Regex;
+
+
+bitflags!(
+    flags RenderMode: u32 {
+        static CpuRendering  = 0x00000001,
+        static GpuRendering  = 0x00000010,
+        static LinuxTarget   = 0x00000100,
+        static MacOsTarget   = 0x00001000,
+        static AndroidTarget = 0x00010000
+    }
+)
+
+
+fn main() {
+    let args = os::args();
+    let mut parts = args.tail().split(|e| "--" == e.as_slice());
+
+    let harness_args = parts.next().unwrap();  // .split() is never empty
+    let servo_args = parts.next().unwrap_or(&[]);
+
+    let (render_mode_string, base_path, testname) = match harness_args {
+        [] | [_] => fail!("USAGE: cpu|gpu base_path [testname regex]"),
+        [ref render_mode_string, ref base_path] => (render_mode_string, base_path, None),
+        [ref render_mode_string, ref base_path, ref testname, ..] => (render_mode_string, base_path, Some(Regex::new(testname.as_slice()).unwrap())),
+    };
+
+    let mut render_mode = match render_mode_string.as_slice() {
+        "cpu" => CpuRendering,
+        "gpu" => GpuRendering,
+        _ => fail!("First argument must specify cpu or gpu as rendering mode")
+    };
+    if cfg!(target_os = "linux") {
+        render_mode.insert(LinuxTarget);
+    }
+    if cfg!(target_os = "macos") {
+        render_mode.insert(MacOsTarget);
+    }
+    if cfg!(target_os = "android") {
+        render_mode.insert(AndroidTarget);
+    }
+
+    let mut all_tests = vec!();
+    println!("Scanning {} for manifests\n", base_path);
+
+    for file in io::fs::walk_dir(&Path::new(base_path.as_slice())).unwrap() {
+        let maybe_extension = file.extension_str();
+        match maybe_extension {
+            Some(extension) => {
+                if extension.to_ascii_lower().as_slice() == "list" && file.is_file() {
+                    let manifest = file.as_str().unwrap();
+                    let tests = parse_lists(manifest, servo_args, render_mode);
+                    println!("\t{} [{} tests]", manifest, tests.len());
+                    all_tests.push_all_move(tests);
+                }
+            }
+            _ => {}
+        }
+    }
+
+    let test_opts = TestOpts {
+        filter: testname,
+        run_ignored: false,
+        logfile: None,
+        run_tests: true,
+        run_benchmarks: false,
+        ratchet_noise_percent: None,
+        ratchet_metrics: None,
+        save_metrics: None,
+        test_shard: None,
+        nocapture: false,
+        color: AutoColor
+    };
+
+    match run_tests_console(&test_opts, all_tests) {
+        Ok(false) => os::set_exit_status(1), // tests failed
+        Err(_) => os::set_exit_status(2),    // I/O-related failure
+        _ => (),
+    }
+}
+
+#[deriving(PartialEq)]
+enum ReftestKind {
+    Same,
+    Different,
+}
+
+struct Reftest {
+    name: String,
+    kind: ReftestKind,
+    files: [String, ..2],
+    id: uint,
+    servo_args: Vec<String>,
+    render_mode: RenderMode,
+<<<<<<< HEAD
+    is_flaky: bool,
+||||||| merged common ancestors
+    flakiness: uint,
+=======
+    flakiness: uint,
+    experimental: bool,
+>>>>>>> Reftests can opt into --experimental
+}
+
+struct TestLine<'a> {
+    conditions: &'a str,
+    kind: &'a str,
+    file_left: &'a str,
+    file_right: &'a str,
+}
+
+fn parse_lists(file: &str, servo_args: &[String], render_mode: RenderMode) -> Vec<TestDescAndFn> {
+    let mut tests = Vec::new();
+    let mut next_id = 0;
+    let file_path = Path::new(file);
+    let contents = File::open_mode(&file_path, io::Open, io::Read)
+                       .and_then(|mut f| f.read_to_string())
+                       .ok().expect("Could not read file");
+
+    for line in contents.as_slice().lines() {
+<<<<<<< HEAD
+        // ignore comments or empty lines
+        if line.starts_with("#") || line.is_empty() {
+            continue;
+        }
+
+        let parts: Vec<&str> = line.split(' ').filter(|p| !p.is_empty()).collect();
+
+        let test_line = match parts.len() {
+            3 => TestLine {
+                conditions: "",
+                kind: parts[0],
+                file_left: parts[1],
+                file_right: parts[2],
+||||||| merged common ancestors
+       // ignore comments or empty lines
+       if line.starts_with("#") || line.is_empty() {
+          continue;
+       }
+
+       let parts: Vec<&str> = line.split(' ').filter(|p| !p.is_empty()).collect();
+
+       let test_line = match parts.len() {
+          3 => {
+            TestLine {
+              conditions: "",
+              kind: parts[0],
+              file_left: parts[1],
+              file_right: parts[2],
+            }
+          },
+          4 => {
+            TestLine {
+              conditions: parts[0],
+              kind: parts[1],
+              file_left: parts[2],
+              file_right: parts[3],
+            }
+          },
+          _ => {
+            fail!("reftest line: '{:s}' doesn't match '[CONDITIONS] KIND LEFT RIGHT'", line);
+          }
+       };
+
+       let kind = match test_line.kind {
+          "==" => Same,
+          "!=" => Different,
+          part => fail!("reftest line: '{:s}' has invalid kind '{:s}'", line, part)
+       };
+       let src_path = file_path.dir_path();
+       let src_dir = src_path.display().to_string();
+       let file_left =  src_dir.clone().append("/").append(test_line.file_left);
+       let file_right = src_dir.append("/").append(test_line.file_right);
+
+       let mut conditions_list = test_line.conditions.split(',');
+       let mut flakiness = 0;
+       for condition in conditions_list {
+          match condition {
+            "flaky_cpu" => {
+              flakiness |= CpuRendering as uint;
+=======
+       // ignore comments or empty lines
+       if line.starts_with("#") || line.is_empty() {
+          continue;
+       }
+
+       let parts: Vec<&str> = line.split(' ').filter(|p| !p.is_empty()).collect();
+
+       let test_line = match parts.len() {
+          3 => {
+            TestLine {
+              conditions: "",
+              kind: parts[0],
+              file_left: parts[1],
+              file_right: parts[2],
+            }
+          },
+          4 => {
+            TestLine {
+              conditions: parts[0],
+              kind: parts[1],
+              file_left: parts[2],
+              file_right: parts[3],
+            }
+          },
+          _ => {
+            fail!("reftest line: '{:s}' doesn't match '[CONDITIONS] KIND LEFT RIGHT'", line);
+          }
+       };
+
+       let kind = match test_line.kind {
+          "==" => Same,
+          "!=" => Different,
+          part => fail!("reftest line: '{:s}' has invalid kind '{:s}'", line, part)
+       };
+       let src_path = file_path.dir_path();
+       let src_dir = src_path.display().to_string();
+       let file_left =  src_dir.clone().append("/").append(test_line.file_left);
+       let file_right = src_dir.append("/").append(test_line.file_right);
+
+       let mut conditions_list = test_line.conditions.split(',');
+       let mut flakiness = 0;
+       let mut experimental = false;
+       for condition in conditions_list {
+          match condition {
+            "flaky_cpu" => {
+              flakiness |= CpuRendering as uint;
+>>>>>>> Reftests can opt into --experimental
+            },
+            4 => TestLine {
+                conditions: parts[0],
+                kind: parts[1],
+                file_left: parts[2],
+                file_right: parts[3],
+            },
+<<<<<<< HEAD
+            _ => fail!("reftest line: '{:s}' doesn't match '[CONDITIONS] KIND LEFT RIGHT'", line),
+        };
+
+        let kind = match test_line.kind {
+            "==" => Same,
+            "!=" => Different,
+            part => fail!("reftest line: '{:s}' has invalid kind '{:s}'", line, part)
+        };
+        let src_path = file_path.dir_path();
+        let src_dir = src_path.display().to_string();
+        let file_left =  src_dir.clone().append("/").append(test_line.file_left);
+        let file_right = src_dir.append("/").append(test_line.file_right);
+
+        let mut conditions_list = test_line.conditions.split(',');
+        let mut flakiness = RenderMode::empty();
+        for condition in conditions_list {
+            match condition {
+                "flaky_cpu" => flakiness.insert(CpuRendering),
+                "flaky_gpu" => flakiness.insert(GpuRendering),
+                "flaky_linux" => flakiness.insert(LinuxTarget),
+                "flaky_macos" => flakiness.insert(MacOsTarget),
+                _ => (),
+            }
+        }
+
+        let reftest = Reftest {
+            name: format!("{} {} {}", test_line.file_left, test_line.kind, test_line.file_right),
+            kind: kind,
+            files: [file_left, file_right],
+            id: next_id,
+            render_mode: render_mode,
+            servo_args: servo_args.iter().map(|x| x.clone()).collect(),
+            is_flaky: render_mode.intersects(flakiness),
+        };
+
+        next_id += 1;
+
+        tests.push(make_test(reftest));
+||||||| merged common ancestors
+            _ => {}
+          }
+       }
+
+       let reftest = Reftest {
+         name: test_line.file_left.to_string().append(" / ").append(test_line.file_right),
+         kind: kind,
+         files: [file_left, file_right],
+         id: next_id,
+         render_mode: render_mode,
+         servo_args: servo_args.iter().map(|x| x.clone()).collect(),
+         flakiness: flakiness,
+       };
+
+       next_id += 1;
+
+       tests.push(make_test(reftest));
+=======
+            "experimental" => {
+                experimental = true;
+            },
+            _ => {}
+          }
+       }
+
+       let reftest = Reftest {
+         name: test_line.file_left.to_string().append(" / ").append(test_line.file_right),
+         kind: kind,
+         files: [file_left, file_right],
+         id: next_id,
+         render_mode: render_mode,
+         servo_args: servo_args.iter().map(|x| x.clone()).collect(),
+         flakiness: flakiness,
+         experimental: experimental,
+       };
+
+       next_id += 1;
+
+       tests.push(make_test(reftest));
+>>>>>>> Reftests can opt into --experimental
+    }
+    tests
+}
+
+fn make_test(reftest: Reftest) -> TestDescAndFn {
+    let name = reftest.name.clone();
+    TestDescAndFn {
+        desc: TestDesc {
+            name: DynTestName(name),
+            ignore: false,
+            should_fail: false,
+        },
+        testfn: DynTestFn(proc() {
+            check_reftest(reftest);
+        }),
+    }
+}
+
+fn capture(reftest: &Reftest, side: uint) -> png::Image {
+    let filename = format!("/tmp/servo-reftest-{:06u}-{:u}.png", reftest.id, side);
+    let mut args = reftest.servo_args.clone();
+    // GPU rendering is the default
+    if reftest.render_mode.contains(CpuRendering) {
+        args.push("-c".to_string());
+    }
+    if reftest.experimental {
+        args.push("--experimental".to_string());
+    }
+    args.push_all(["-f".to_string(), "-o".to_string(), filename.clone(),
+                   reftest.files[side].clone()]);
+
+    let retval = match Command::new("./servo").args(args.as_slice()).status() {
+        Ok(status) => status,
+        Err(e) => fail!("failed to execute process: {}", e),
+    };
+    assert!(retval == ExitStatus(0));
+
+    png::load_png(&from_str::<Path>(filename.as_slice()).unwrap()).unwrap()
+}
+
+fn check_reftest(reftest: Reftest) {
+    let left  = capture(&reftest, 0);
+    let right = capture(&reftest, 1);
+
+    let pixels = left.pixels.iter().zip(right.pixels.iter()).map(|(&a, &b)| {
+        if a as i8 - b as i8 == 0 {
+            // White for correct
+            0xFF
+        } else {
+            // "1100" in the RGBA channel with an error for an incorrect value
+            // This results in some number of C0 and FFs, which is much more
+            // readable (and distinguishable) than the previous difference-wise
+            // scaling but does not require reconstructing the actual RGBA pixel.
+            0xC0
+        }
+    }).collect::<Vec<u8>>();
+
+    if pixels.iter().any(|&a| a < 255) {
+        let output_str = format!("/tmp/servo-reftest-{:06u}-diff.png", reftest.id);
+        let output = from_str::<Path>(output_str.as_slice()).unwrap();
+
+        let mut img = png::Image {
+            width: left.width,
+            height: left.height,
+            color_type: png::RGBA8,
+            pixels: pixels,
+        };
+        let res = png::store_png(&mut img, &output);
+        assert!(res.is_ok());
+
+        match (reftest.kind, reftest.is_flaky) {
+            (Same, true) => println!("flaky test - rendering difference: {}", output_str),
+            (Same, false) => fail!("rendering difference: {}", output_str),
+            (Different, _) => {}   // Result was different and that's what was expected
+        }
+    } else {
+        assert!(reftest.is_flaky || reftest.kind == Same);
+    }
+}
diff --git a/src/test/ref/basic.list b/src/test/ref/basic.list
index 13835bf64ee..9884fe140b4 100644
--- a/src/test/ref/basic.list
+++ b/src/test/ref/basic.list
@@ -86,6 +86,7 @@ flaky_cpu == linebreak_simple_a.html linebreak_simple_b.html
 == position_fixed_overflow_a.html position_fixed_overflow_b.html
 == noscript.html noscript_ref.html
 == pseudo_inherit.html pseudo_inherit_ref.html
+experimental == vertical-lr-blocks.html vertical-lr-blocks_ref.html
 == float_intrinsic_height.html float_intrinsic_height_ref.html
 == table_auto_width.html table_auto_width_ref.html
 == inline_whitespace_b.html inline_whitespace_ref.html
diff --git a/src/test/ref/vertical-lr-blocks.html b/src/test/ref/vertical-lr-blocks.html
new file mode 100644
index 00000000000..c68fee90788
--- /dev/null
+++ b/src/test/ref/vertical-lr-blocks.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<html>
+<head>
+<style>
+html { writing-mode: vertical-rl }
+body { margin: 10px }
+div { border: blue solid 5px; line-height: 30px; height: 500px }
+p { background: green; margin: 40px 20px }
+p + p { margin-top: 60px }
+</style>
+</head>
+<body>
+<div>
+<p>&nbsp;</p>
+<p>&nbsp;</p>
+</div>
+</body>
+</html>
diff --git a/src/test/ref/vertical-lr-blocks_ref.html b/src/test/ref/vertical-lr-blocks_ref.html
new file mode 100644
index 00000000000..8581695c49f
--- /dev/null
+++ b/src/test/ref/vertical-lr-blocks_ref.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<html>
+<head>
+<style>
+div { border: blue solid 5px; position: absolute;
+      top: 10px; right: 10px; bottom: 10px; width: 120px; height: 500px }
+p { background: green; margin: 0; position: absolute;
+    top: 40px; right: 20px; bottom: 40px; width: 30px }
+p + p { right: 70px; top: 60px }
+</style>
+</head>
+<body>
+<div>
+<p>&nbsp;</p>
+<p>&nbsp;</p>
+</div>
+</body>
+</html>