[core] Add unit test for zero width space line breaking

2 files changed, 96 insertions, 0 deletions

diff --git a/test/test-files.json b/test/test-files.json
index 034bf29b90..6ed78d4e61 100644
--- a/test/test-files.json
+++ b/test/test-files.json
@@ -70,6 +70,7 @@
         "test/text/language_tag.test.cpp",
         "test/text/local_glyph_rasterizer.test.cpp",
         "test/text/quads.test.cpp",
+        "test/text/shaping.test.cpp",
         "test/text/tagged_string.test.cpp",
         "test/tile/custom_geometry_tile.test.cpp",
         "test/tile/geojson_tile.test.cpp",
diff --git a/test/text/shaping.test.cpp b/test/text/shaping.test.cpp
new file mode 100644
index 0000000000..547c85e5ba
--- /dev/null
+++ b/test/text/shaping.test.cpp
@@ -0,0 +1,95 @@
+
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/text/bidi.hpp>
+#include <mbgl/text/tagged_string.hpp>
+#include <mbgl/text/shaping.hpp>
+#include <mbgl/util/constants.hpp>
+
+using namespace mbgl;
+using namespace util;
+
+TEST(Shaping, ZWSP) {
+    Glyph glyph;
+    glyph.id = u'中';
+    glyph.metrics.width = 18;
+    glyph.metrics.height = 18;
+    glyph.metrics.left = 2;
+    glyph.metrics.top = -8;
+    glyph.metrics.advance = 21;
+
+    BiDi bidi;
+    auto immutableGlyph = Immutable<Glyph>(makeMutable<Glyph>(std::move(glyph)));
+    const std::vector<std::string> fontStack{{"font-stack"}};
+    const SectionOptions sectionOptions(1.0f, fontStack);
+    GlyphMap glyphs = {
+        { FontStackHasher()(fontStack), {{u'中', std::move(immutableGlyph)}} }
+    };
+
+    const auto testGetShaping = [&] (const TaggedString& string, unsigned maxWidthInChars) {
+        return getShaping(string,
+                          maxWidthInChars * ONE_EM,
+                          ONE_EM,       // lineHeight
+                          style::SymbolAnchorType::Center,
+                          style::TextJustifyType::Center,
+                          0,            // spacing
+                          {0.0f, 0.0f}, // translate
+                          WritingModeType::Horizontal,
+                          bidi,
+                          glyphs);
+    };
+
+    // 3 lines
+    // 中中中中中中
+    // 中中中中中中
+    // 中中
+    {
+        TaggedString string(u"中中\u200b中中\u200b中中\u200b中中中中中中\u200b中中", sectionOptions);
+        auto shaping = testGetShaping(string, 5);
+        ASSERT_EQ(shaping.lineCount, 3);
+        ASSERT_EQ(shaping.top, -36);
+        ASSERT_EQ(shaping.bottom, 36);
+        ASSERT_EQ(shaping.left, -63);
+        ASSERT_EQ(shaping.right, 63);
+        ASSERT_EQ(shaping.writingMode, WritingModeType::Horizontal);
+    }
+
+    // 2 lines
+    // 中中
+    // 中
+    {
+        TaggedString string(u"中中\u200b中", sectionOptions);
+        auto shaping = testGetShaping(string, 1);
+        ASSERT_EQ(shaping.lineCount, 2);
+        ASSERT_EQ(shaping.top, -24);
+        ASSERT_EQ(shaping.bottom, 24);
+        ASSERT_EQ(shaping.left, -21);
+        ASSERT_EQ(shaping.right, 21);
+        ASSERT_EQ(shaping.writingMode, WritingModeType::Horizontal);
+    }
+
+    // 1 line
+    // 中中
+    {
+        TaggedString string(u"中中\u200b", sectionOptions);
+        auto shaping = testGetShaping(string, 2);
+        ASSERT_EQ(shaping.lineCount, 1);
+        ASSERT_EQ(shaping.top, -12);
+        ASSERT_EQ(shaping.bottom, 12);
+        ASSERT_EQ(shaping.left, -21);
+        ASSERT_EQ(shaping.right, 21);
+        ASSERT_EQ(shaping.writingMode, WritingModeType::Horizontal);
+    }
+
+    // 5 'new' lines.
+    {
+        TaggedString string(u"\u200b\u200b\u200b\u200b\u200b", sectionOptions);
+        auto shaping = testGetShaping(string, 1);
+        ASSERT_EQ(shaping.lineCount, 5);
+        ASSERT_EQ(shaping.top, -60);
+        ASSERT_EQ(shaping.bottom, 60);
+        ASSERT_EQ(shaping.left, 0);
+        ASSERT_EQ(shaping.right, 0);
+        ASSERT_EQ(shaping.writingMode, WritingModeType::Horizontal);
+    }
+}