[core] Add unit test for calculateTileDistances

next/test/CMakeLists.txt

@@ -64,6 +64,7 @@ add_library(
     ${MBGL_ROOT}/test/style/style_layer.test.cpp
     ${MBGL_ROOT}/test/style/style_parser.test.cpp
     ${MBGL_ROOT}/test/text/bidi.test.cpp
+    ${MBGL_ROOT}/test/text/calculate_tile_distances.test.cpp
     ${MBGL_ROOT}/test/text/cross_tile_symbol_index.test.cpp
     ${MBGL_ROOT}/test/text/formatted.test.cpp
     ${MBGL_ROOT}/test/text/get_anchors.test.cpp

src/mbgl/layout/symbol_layout.cpp

@@ -693,12 +693,12 @@ bool SymbolLayout::anchorIsTooClose(const std::u16string& text, const float repe
 
 // Analog of `addToLineVertexArray` in JS. This version doesn't need to build up a line array like the
 // JS version does, but it uses the same logic to calculate tile distances.
-std::vector<float> CalculateTileDistances(const GeometryCoordinates& line, const Anchor& anchor) {
+std::vector<float> SymbolLayout::calculateTileDistances(const GeometryCoordinates& line, const Anchor& anchor) {
     std::vector<float> tileDistances(line.size());
     if (anchor.segment) {
         std::size_t segment = *anchor.segment;
         assert(segment < line.size());
-        auto sumForwardLength = util::dist<float>(anchor.point, line[segment + 1]);
+        auto sumForwardLength = (segment + 1 < line.size()) ? util::dist<float>(anchor.point, line[segment + 1]) : .0f;
         auto sumBackwardLength = util::dist<float>(anchor.point, line[segment]);
         for (std::size_t i = segment + 1; i < line.size(); ++i) {
             tileDistances[i] = sumForwardLength;
@@ -842,7 +842,7 @@ std::size_t SymbolLayout::addSymbolGlyphQuads(SymbolBucket& bucket,
                                            symbolInstance.textOffset,
                                            writingMode,
                                            symbolInstance.line(),
-                                           CalculateTileDistances(symbolInstance.line(), symbolInstance.anchor),
+                                           calculateTileDistances(symbolInstance.line(), symbolInstance.anchor),
                                            placedIconIndex);
     placedIndex = bucket.text.placedSymbols.size() - 1;
     PlacedSymbol& placedSymbol = bucket.text.placedSymbols.back();

src/mbgl/layout/symbol_layout.hpp

@@ -55,7 +55,8 @@ class SymbolLayout final : public Layout {
      * @return std::array<float, 2> offset along x- and y- axis correspondingly.
      */
     static std::array<float, 2> evaluateVariableOffset(style::SymbolAnchorType anchor, std::array<float, 2> textOffset);
-
+
+    static std::vector<float> calculateTileDistances(const GeometryCoordinates& line, const Anchor& anchor);
 
 private:
     void addFeature(const size_t,

test/test-files.json

@@ -66,6 +66,7 @@
         "test/style/style_layer.test.cpp",
         "test/style/style_parser.test.cpp",
         "test/text/bidi.test.cpp",
+        "test/text/calculate_tile_distances.test.cpp",
         "test/text/cross_tile_symbol_index.test.cpp",
         "test/text/formatted.test.cpp",
         "test/text/get_anchors.test.cpp",

test/text/calculate_tile_distances.test.cpp

@@ -0,0 +1,27 @@
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/geometry/anchor.hpp>
+#include <mbgl/layout/symbol_layout.hpp>
+#include <mbgl/tile/geometry_tile_data.hpp>
+
+using namespace mbgl;
+
+TEST(calculateTileDistances, Point) {
+    const GeometryCoordinates line = {Point<int16_t>{1, 1}};
+    const auto distances = SymbolLayout::calculateTileDistances(line, Anchor(1.0f, 1.0f, .0f, 0u));
+    EXPECT_EQ(distances.size(), 1u);
+    EXPECT_EQ(distances[0], .0f);
+}
+
+TEST(calculateTileDistances, Line) {
+    const GeometryCoordinates line = {
+        Point<int16_t>{1, 1}, Point<int16_t>{1, 2}, Point<int16_t>{1, 3}, Point<int16_t>{1, 4}};
+    const auto distances = SymbolLayout::calculateTileDistances(line, Anchor(1.0f, 3.0f, .0f, 2u));
+    EXPECT_EQ(distances, std::vector<float>({2.0f, 1.0f, 0.0f, 1.0f}));
+}
+
+TEST(calculateTileDistances, EmptySegment) {
+    const GeometryCoordinates line = {};
+    const auto distances = SymbolLayout::calculateTileDistances(line, Anchor(1.0f, 1.0f, .0f));
+    EXPECT_EQ(distances.size(), 0u);
+}