[core] Use UTF-16 instead of UTF-32 for label features to avoid extra conversions and reduce in-memory size.

Continue to use uint32 as glyph ID to maintain Glyph PBF, even though we're only using 16 bits of that uint32.
Use std::codecvt instead of boost::unicode_iterator for UTF8->UTF16 conversions.

6 files changed, 10 insertions, 10 deletions

diff --git a/src/mbgl/text/glyph.cpp b/src/mbgl/text/glyph.cpp
index a877d7a799..29929b73e6 100644
--- a/src/mbgl/text/glyph.cpp
+++ b/src/mbgl/text/glyph.cpp
@@ -3,7 +3,7 @@
 namespace mbgl {
 
 // Note: this only works for the BMP
-GlyphRange getGlyphRange(char32_t glyph) {
+GlyphRange getGlyphRange(char16_t glyph) {
     unsigned start = (glyph/256) * 256;
     unsigned end = (start + 255);
     if (start > 65280) start = 65280;
diff --git a/src/mbgl/text/glyph.hpp b/src/mbgl/text/glyph.hpp
index a333f68ff4..d07fbdff21 100644
--- a/src/mbgl/text/glyph.hpp
+++ b/src/mbgl/text/glyph.hpp
@@ -11,7 +11,7 @@
 namespace mbgl {
 
 // Note: this only works for the BMP
-GlyphRange getGlyphRange(char32_t glyph);
+GlyphRange getGlyphRange(char16_t glyph);
 
 struct GlyphMetrics {
     explicit operator bool() const {
@@ -63,10 +63,10 @@ public:
 class Shaping {
     public:
     explicit Shaping() : top(0), bottom(0), left(0), right(0) {}
-    explicit Shaping(float x, float y, std::u32string text_)
+    explicit Shaping(float x, float y, std::u16string text_)
         : text(std::move(text_)), top(y), bottom(y), left(x), right(x) {}
     std::vector<PositionedGlyph> positionedGlyphs;
-    std::u32string text;
+    std::u16string text;
     int32_t top;
     int32_t bottom;
     int32_t left;
diff --git a/src/mbgl/text/glyph_atlas.cpp b/src/mbgl/text/glyph_atlas.cpp
index 031e89d13a..57b8b14017 100644
--- a/src/mbgl/text/glyph_atlas.cpp
+++ b/src/mbgl/text/glyph_atlas.cpp
@@ -81,7 +81,7 @@ void GlyphAtlas::setObserver(GlyphAtlasObserver* observer_) {
 }
 
 void GlyphAtlas::addGlyphs(uintptr_t tileUID,
-                           const std::u32string& text,
+                           const std::u16string& text,
                            const FontStack& fontStack,
                            const GlyphSet& glyphSet,
                            GlyphPositions& face)
@@ -90,7 +90,7 @@ void GlyphAtlas::addGlyphs(uintptr_t tileUID,
 
     const std::map<uint32_t, SDFGlyph>& sdfs = glyphSet.getSDFs();
 
-    for (uint32_t chr : text)
+    for (char16_t chr : text)
     {
         auto sdf_it = sdfs.find(chr);
         if (sdf_it == sdfs.end()) {
diff --git a/src/mbgl/text/glyph_atlas.hpp b/src/mbgl/text/glyph_atlas.hpp
index 550ca4cc17..af14aace5b 100644
--- a/src/mbgl/text/glyph_atlas.hpp
+++ b/src/mbgl/text/glyph_atlas.hpp
@@ -55,7 +55,7 @@ public:
     void setObserver(GlyphAtlasObserver* observer);
 
     void addGlyphs(uintptr_t tileUID,
-                   const std::u32string& text,
+                   const std::u16string& text,
                    const FontStack&,
                    const GlyphSet&,
                    GlyphPositions&);
diff --git a/src/mbgl/text/glyph_set.cpp b/src/mbgl/text/glyph_set.cpp
index c778de207b..f0e3991540 100644
--- a/src/mbgl/text/glyph_set.cpp
+++ b/src/mbgl/text/glyph_set.cpp
@@ -31,7 +31,7 @@ const std::map<uint32_t, SDFGlyph> &GlyphSet::getSDFs() const {
     return sdfs;
 }
 
-const Shaping GlyphSet::getShaping(const std::u32string &string, const float maxWidth,
+const Shaping GlyphSet::getShaping(const std::u16string &string, const float maxWidth,
                                     const float lineHeight, const float horizontalAlign,
                                     const float verticalAlign, const float justify,
                                     const float spacing, const Point<float> &translate) const {
@@ -44,7 +44,7 @@ const Shaping GlyphSet::getShaping(const std::u32string &string, const float max
     const float y = yOffset;
 
     // Loop through all characters of this label and shape.
-    for (uint32_t chr : string) {
+    for (char16_t chr : string) {
         auto it = sdfs.find(chr);
         if (it != sdfs.end()) {
             shaping.positionedGlyphs.emplace_back(chr, x, y);
diff --git a/src/mbgl/text/glyph_set.hpp b/src/mbgl/text/glyph_set.hpp
index fed7960a5f..004cae343d 100644
--- a/src/mbgl/text/glyph_set.hpp
+++ b/src/mbgl/text/glyph_set.hpp
@@ -9,7 +9,7 @@ class GlyphSet {
 public:
     void insert(uint32_t id, SDFGlyph&&);
     const std::map<uint32_t, SDFGlyph> &getSDFs() const;
-    const Shaping getShaping(const std::u32string &string, float maxWidth, float lineHeight,
+    const Shaping getShaping(const std::u16string &string, float maxWidth, float lineHeight,
                              float horizontalAlign, float verticalAlign, float justify,
                              float spacing, const Point<float> &translate) const;
     void lineWrap(Shaping &shaping, float lineHeight, float maxWidth, float horizontalAlign,