From 4c249968d90ecf434c0308e2ea3558d312b6f359 Mon Sep 17 00:00:00 2001
From: Cameron McCormack <cam@mcc.id.au>
Date: Tue, 10 May 2016 10:58:03 +1000
Subject: [PATCH] Round border-*-width values to pixels in geckolib.

---
 ports/geckolib/properties.mako.rs | 11 +++++++++--
 ports/geckolib/values.rs          | 14 ++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/ports/geckolib/properties.mako.rs b/ports/geckolib/properties.mako.rs
index 4037ea58fe1..a4d5b2a3cd1 100644
--- a/ports/geckolib/properties.mako.rs
+++ b/ports/geckolib/properties.mako.rs
@@ -31,6 +31,7 @@ use style::properties::make_cascade_vec;
 use style::properties::style_struct_traits::*;
 use gecko_style_structs::{nsStyleUnion, nsStyleUnit};
 use values::{ToGeckoStyleCoord, convert_rgba_to_nscolor, convert_nscolor_to_rgba};
+use values::round_border_to_device_pixels;
 
 #[derive(Clone)]
 pub struct GeckoComputedValues {
@@ -264,9 +265,14 @@ def set_gecko_property(ffi_name, expr):
 <%call expr="impl_color_copy(ident, gecko_ffi_name, color_flags_ffi_name)"></%call>
 </%def>
 
-<%def name="impl_app_units(ident, gecko_ffi_name, need_clone)">
+<%def name="impl_app_units(ident, gecko_ffi_name, need_clone, round_to_pixels=False)">
     fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
+        % if round_to_pixels:
+        let au_per_device_px = Au(self.gecko.mTwipsPerPixel);
+        self.gecko.${gecko_ffi_name} = round_border_to_device_pixels(v, au_per_device_px).0;
+        % else:
         self.gecko.${gecko_ffi_name} = v.0;
+        % endif
     }
 <%call expr="impl_simple_copy(ident, gecko_ffi_name)"></%call>
 %if need_clone:
@@ -499,7 +505,8 @@ fn static_assert() {
     <% impl_color("border_%s_color" % side.ident, "mBorderColor[%s]" % side.index,
                   color_flags_ffi_name="mBorderStyle[%s]" % side.index) %>
 
-    <% impl_app_units("border_%s_width" % side.ident, "mComputedBorder.%s" % side.ident, need_clone=False) %>
+    <% impl_app_units("border_%s_width" % side.ident, "mComputedBorder.%s" % side.ident, need_clone=False,
+                      round_to_pixels=True) %>
 
     fn border_${side.ident}_has_nonzero_width(&self) -> bool {
         self.gecko.mComputedBorder.${side.ident} != 0
diff --git a/ports/geckolib/values.rs b/ports/geckolib/values.rs
index 172ce193b8a..03dd8ffeb58 100644
--- a/ports/geckolib/values.rs
+++ b/ports/geckolib/values.rs
@@ -2,8 +2,10 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use app_units::Au;
 use cssparser::RGBA;
 use gecko_style_structs::{nsStyleUnion, nsStyleUnit};
+use std::cmp::max;
 use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto, LengthOrPercentageOrNone};
 
 pub trait ToGeckoStyleCoord {
@@ -81,3 +83,15 @@ pub fn convert_nscolor_to_rgba(color: u32) -> RGBA {
         alpha: (((color >> 24) & 0xff) as f32) / 255.0,
     }
 }
+
+#[inline]
+pub fn round_border_to_device_pixels(width: Au, au_per_device_px: Au) -> Au {
+    // Round width down to the nearest device pixel, but any non-zero value that
+    // would round down to zero is clamped to 1 device pixel.  Used for storing
+    // computed values of border-*-width and outline-width.
+    if width == Au(0) {
+        Au(0)
+    } else {
+        max(au_per_device_px, Au(width.0 / au_per_device_px.0 * au_per_device_px.0))
+    }
+}