Bug 1279069 - Replace &nbsp; with <space> for Graphite shaping purposes if &nbsp; is not supported by the font. r=jrmuizel

gfx/thebes/gfxGraphiteShaper.cpp

@@ -1,5 +1,5 @@
-/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */
 
@@ -159,6 +159,21 @@ gfxGraphiteShaper::ShapeText(DrawTarget      *aDrawTarget,
                       AddFeature,
                       &f);
 
+    // Graphite shaping doesn't map U+00a0 (nbsp) to space if it is missing
+    // from the font, so check for that possibility. (Most fonts double-map
+    // the space glyph to both 0x20 and 0xA0, so this won't often be needed;
+    // so we don't copy the text until we know it's required.)
+    nsAutoString transformed;
+    const char16_t NO_BREAK_SPACE = 0x00a0;
+    if (!entry->HasCharacter(NO_BREAK_SPACE)) {
+        nsDependentSubstring src(aText, aLength);
+        if (src.FindChar(NO_BREAK_SPACE) != kNotFound) {
+            transformed = src;
+            transformed.ReplaceChar(NO_BREAK_SPACE, ' ');
+            aText = transformed.BeginReading();
+        }
+    }
+
     size_t numChars = gr_count_unicode_characters(gr_utf16,
                                                   aText, aText + aLength,
                                                   nullptr);