servo: Merge #13924 - implemented string-valued text-overflow (from cynicaldevil:text-overflow); r=emilio

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---

<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #13709

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- [x] There are tests for these changes

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cc @Manishearth
The lorem-ipsum example from MDN works as expected.

Source-Repo: https://github.com/servo/servo
Source-Revision: a91f48ee05933784630fdf918fc4b66037dba9f1

servo/components/layout/fragment.rs

@@ -1037,12 +1037,15 @@ impl Fragment {
     }
 
     /// Transforms this fragment into an ellipsis fragment, preserving all the other data.
-    pub fn transform_into_ellipsis(&self, layout_context: &LayoutContext) -> Fragment {
+    pub fn transform_into_ellipsis(&self,
+                                   layout_context: &LayoutContext,
+                                   text_overflow_string: String)
+                                   -> Fragment {
         let mut unscanned_ellipsis_fragments = LinkedList::new();
         unscanned_ellipsis_fragments.push_back(self.transform(
                 self.border_box.size,
                 SpecificFragmentInfo::UnscannedText(
-                    box UnscannedTextFragmentInfo::new("…".to_owned(), None))));
+                    box UnscannedTextFragmentInfo::new(text_overflow_string, None))));
         let ellipsis_fragments = TextRunScanner::new().scan_for_runs(&mut layout_context.font_context(),
                                                                      unscanned_ellipsis_fragments);
         debug_assert!(ellipsis_fragments.len() == 1);

servo/components/layout/inline.rs

@@ -31,10 +31,10 @@ use std::collections::VecDeque;
 use std::sync::Arc;
 use style::arc_ptr_eq;
 use style::computed_values::{display, overflow_x, position, text_align, text_justify};
-use style::computed_values::{text_overflow, vertical_align, white_space};
+use style::computed_values::{vertical_align, white_space};
 use style::context::{SharedStyleContext, StyleContext};
 use style::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
-use style::properties::ServoComputedValues;
+use style::properties::{longhands, ServoComputedValues};
 use style::servo::restyle_damage::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW, REPOSITION, RESOLVE_GENERATED_CONTENT};
 use text;
 use unicode_bidi;
@@ -684,21 +684,30 @@ impl LineBreaker {
         }
 
         // Determine if an ellipsis will be necessary to account for `text-overflow`.
-        let mut need_ellipsis = false;
         let available_inline_size = self.pending_line.green_zone.inline -
             self.pending_line.bounds.size.inline - indentation;
-        match (fragment.style().get_text().text_overflow,
-               fragment.style().get_box().overflow_x) {
-            (text_overflow::T::clip, _) | (_, overflow_x::T::visible) => {}
-            (text_overflow::T::ellipsis, _) => {
-                need_ellipsis = fragment.margin_box_inline_size() > available_inline_size;
-            }
-        }
 
-        if !need_ellipsis {
-            self.push_fragment_to_line_ignoring_text_overflow(fragment, layout_context);
-        } else {
-            let ellipsis = fragment.transform_into_ellipsis(layout_context);
+        let ellipsis = match (&fragment.style().get_text().text_overflow.first,
+            fragment.style().get_box().overflow_x) {
+            (&longhands::text_overflow::Side::Clip, _) | (_, overflow_x::T::visible) => None,
+            (&longhands::text_overflow::Side::Ellipsis, _) => {
+                if fragment.margin_box_inline_size() > available_inline_size {
+                    Some("…".to_string())
+                } else {
+                    None
+                }
+            },
+            (&longhands::text_overflow::Side::String(ref string), _) => {
+                if fragment.margin_box_inline_size() > available_inline_size {
+                    Some(string.to_string())
+                } else {
+                    None
+                }
+            }
+        };
+
+        if let Some(string) = ellipsis {
+            let ellipsis = fragment.transform_into_ellipsis(layout_context, string);
             if let Some(truncation_info) =
                     fragment.truncate_to_inline_size(available_inline_size -
                                                      ellipsis.margin_box_inline_size()) {
@@ -707,6 +716,8 @@ impl LineBreaker {
                 self.push_fragment_to_line_ignoring_text_overflow(fragment, layout_context);
             }
             self.push_fragment_to_line_ignoring_text_overflow(ellipsis, layout_context);
+        } else {
+            self.push_fragment_to_line_ignoring_text_overflow(fragment, layout_context);
         }
 
         if line_flush_mode == LineFlushMode::Flush {

servo/components/style/properties/longhand/text.mako.rs

@@ -12,9 +12,6 @@
                                              Method("has_overline", "bool"),
                                              Method("has_line_through", "bool")]) %>
 
-% if product == "servo":
-    ${helpers.single_keyword("text-overflow", "clip ellipsis", animatable=False)}
-% else:
 <%helpers:longhand name="text-overflow" animatable="False">
     use std::fmt;
     use style_traits::ToCss;
@@ -93,7 +90,6 @@
         }
     }
 </%helpers:longhand>
-% endif
 
 ${helpers.single_keyword("unicode-bidi",
                          "normal embed isolate bidi-override isolate-override plaintext",