Add disable-canvas-aa option to test runner.

components/canvas/canvas_paint_task.rs

@@ -14,6 +14,7 @@ use geom::size::Size2D;
 use layers::platform::surface::NativeSurface;
 use gfx_traits::color;
 use num::ToPrimitive;
+use util::opts;
 use util::task::spawn_named;
 use util::vec::byte_swap;
 
@@ -174,8 +175,14 @@ struct CanvasPaintState<'a> {
 
 impl<'a> CanvasPaintState<'a> {
     fn new() -> CanvasPaintState<'a> {
+        let antialias = if opts::get().enable_canvas_antialiasing {
+            AntialiasMode::Default
+        } else {
+            AntialiasMode::None
+        };
+
         CanvasPaintState {
-            draw_options: DrawOptions::default(),
+            draw_options: DrawOptions::new(1.0, CompositionOp::Over, antialias),
             fill_style: Pattern::Color(ColorPattern::new(color::black())),
             stroke_style: Pattern::Color(ColorPattern::new(color::black())),
             stroke_opts: StrokeOptions::new(1.0, JoinStyle::MiterOrBevel, CapStyle::Butt, 10.0, &[]),

components/util/opts.rs

@@ -99,6 +99,10 @@ pub struct Opts {
     /// font for layout tests.
     pub enable_text_antialiasing: bool,
 
+    /// If set with --disable-canvas-aa, disable antialiasing on the HTML canvas element.
+    /// Like --disable-text-aa, this is useful for reftests where pixel perfect results are required.
+    pub enable_canvas_antialiasing: bool,
+
     /// True if each step of layout is traced to an external JSON file
     /// for debugging purposes. Settings this implies sequential layout
     /// and paint.
@@ -220,6 +224,7 @@ pub fn default_opts() -> Opts {
         show_debug_parallel_layout: false,
         paint_flashing: false,
         enable_text_antialiasing: false,
+        enable_canvas_antialiasing: false,
         trace_layout: false,
         devtools_port: None,
         webdriver_port: None,
@@ -398,6 +403,7 @@ pub fn from_cmdline_args(args: &[String]) -> bool {
         show_debug_parallel_layout: debug_options.contains(&"show-parallel-layout"),
         paint_flashing: debug_options.contains(&"paint-flashing"),
         enable_text_antialiasing: !debug_options.contains(&"disable-text-aa"),
+        enable_canvas_antialiasing: !debug_options.contains(&"disable-canvas-aa"),
         dump_flow_tree: debug_options.contains(&"dump-flow-tree"),
         dump_display_list: debug_options.contains(&"dump-display-list"),
         dump_display_list_optimized: debug_options.contains(&"dump-display-list-optimized"),