Remove the code which sorts and removes duplicates from the fallback font list

ui/gfx/render_text_harfbuzz.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/render_text_harfbuzz.h"
 
 #include <limits>
+#include <set>
 
 #include "base/i18n/bidi_line_iterator.h"
 #include "base/i18n/break_iterator.h"
 #include "base/i18n/char_iterator.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/trace_event/trace_event.h"
 #include "third_party/harfbuzz-ng/src/hb.h"
 #include "third_party/icu/source/common/unicode/ubidi.h"
@@ skipping 442 matching lines @@
 
   // Size of the multiline text, not including the currently processed line.
   SizeF total_size_;
 
   // The current RTL run segments, to be applied by |UpdateRTLSegmentRanges()|.
   std::vector<SegmentHandle> rtl_segments_;
 
   DISALLOW_COPY_AND_ASSIGN(HarfBuzzLineBreaker);
 };
 
+// Function object for case insensitive string comparison.
+struct CaseInsensitiveCompare {
+  bool operator() (const std::string& a, const std::string& b) const {
+    return base::strncasecmp(a.c_str(), b.c_str(), b.length()) < 0;

[msw, 2015/03/25 23:23:42]

Will strncasecmp work if a.length() != b.length()? Maybe use strcasecmp? 

[ananta, 2015/03/25 23:39:49]

It should. As per docs, it compares upto count characters and stops if
a NULL is seen in either string.

+  }
+};
+
 }  // namespace
 
 namespace internal {
 
 Range RoundRangeF(const RangeF& range_f) {
   return Range(std::floor(range_f.start() + 0.5f),
                std::floor(range_f.end() + 0.5f));
 }
 
 TextRunHarfBuzz::TextRunHarfBuzz()
@@ skipping 819 matching lines @@
   // fallback font list.
   if (!LowerCaseEqualsASCII(primary_family, "segoe ui") &&
       !LowerCaseEqualsASCII(uniscribe_family, "segoe ui")) {
     std::vector<std::string> default_fallback_families =
         GetFallbackFontFamilies("Segoe UI");
     fallback_families.insert(fallback_families.end(),
         default_fallback_families.begin(), default_fallback_families.end());
   }
 #endif
 
-  // Get rid of duplicate fonts in the fallback list. We use the std::unique
-  // algorithm for this. However for this function to work we need to sort
-  // the font list as the unique algorithm relies on duplicates being adjacent.
-  // TODO(ananta)
-  // Sorting the list changes the order in which fonts are evaluated. This may
-  // cause problems in the way some characters appear. It may be best to do
-  // font fallback on the same lines as blink or skia which do this based on
-  // character glyph mapping.
-  std::sort(fallback_families.begin(), fallback_families.end());
-  fallback_families.erase(std::unique(
-      fallback_families.begin(), fallback_families.end()),
-      fallback_families.end());
+  // Use a set to track the fallback fonts and avoid duplicate entries.
+  std::set<std::string, CaseInsensitiveCompare>
+      duplicate_fallback_font_tracker;

[msw, 2015/03/25 23:23:42]

optional nit: rename |tried_fallback_fonts| or similar.

[ananta, 2015/03/25 23:39:49]

Renamed to duplicate_fallback_fonts

[msw, 2015/03/25 23:42:06]

Eh, they aren't duplicate themselves... the name |fallback_fonts| would be okay
with me, given the comment and simple usage.

 
   // Try shaping with the fallback fonts.
   for (const auto& family : fallback_families) {
     if (family == primary_family)
       continue;
 #if defined(OS_WIN)
     if (family == uniscribe_family)
       continue;
 #endif
+    if (duplicate_fallback_font_tracker.find(family) !=
+          duplicate_fallback_font_tracker.end())
+      continue;
+
+    duplicate_fallback_font_tracker.insert(family);
+
     FontRenderParamsQuery query(false);
     query.families.push_back(family);
     query.pixel_size = run->font_size;
     query.style = run->font_style;
     FontRenderParams fallback_render_params = GetFontRenderParams(query, NULL);
     if (CompareFamily(text, family, fallback_render_params, run, &best_family,
                       &best_render_params, &best_missing_glyphs))
       return;
   }
 
@@ skipping 179 matching lines @@
   DCHECK(!update_layout_run_list_);
   DCHECK(!update_display_run_list_);
   return text_elided() ? display_run_list_.get() : &layout_run_list_;
 }
 
 const internal::TextRunList* RenderTextHarfBuzz::GetRunList() const {
   return const_cast<RenderTextHarfBuzz*>(this)->GetRunList();
 }
 
 }  // namespace gfx