[core] improve legibility of labels that follow linesupstream/rebase_text_pitch_scaling

port https://github.com/mapbox/mapbox-gl-js/pull/4781

This improves legibility of labels that follow lines in pitched views.
The previous approach used the limited information in the shader to
calculate put the glyph in approximatelyright place. The new approach
does this more accurately by doing it on the cpu where we have access to
the entire line geometry.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/mbgl/renderer/buckets/symbol_bucket.hpp b/src/mbgl/renderer/buckets/symbol_bucket.hpp
index 002b6e28b3..769841b3a1 100644
--- a/src/mbgl/renderer/buckets/symbol_bucket.hpp
+++ b/src/mbgl/renderer/buckets/symbol_bucket.hpp
@@ -15,6 +15,23 @@
 
 namespace mbgl {
 
+class PlacedSymbol {
+public:
+    PlacedSymbol(Point<float> anchorPoint_, uint16_t segment_, float lowerSize_, float upperSize_,
+            std::array<float, 2> lineOffset_, float placementZoom_, bool vertical_, GeometryCoordinates line_) :
+        anchorPoint(anchorPoint_), segment(segment_), lowerSize(lowerSize_), upperSize(upperSize_),
+        lineOffset(lineOffset_), placementZoom(placementZoom_), vertical(vertical_), line(line_) {}
+    Point<float> anchorPoint;
+    uint16_t segment;
+    float lowerSize;
+    float upperSize;
+    std::array<float, 2> lineOffset;
+    float placementZoom;
+    bool vertical;
+    GeometryCoordinates line;
+    std::vector<float> glyphOffsets;
+};
+
 class SymbolBucket : public Bucket {
 public:
     SymbolBucket(style::SymbolLayoutProperties::PossiblyEvaluated,
@@ -44,10 +61,13 @@ public:
 
     struct TextBuffer {
         gl::VertexVector<SymbolLayoutVertex> vertices;
+        gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex> dynamicVertices;
         gl::IndexVector<gl::Triangles> triangles;
         gl::SegmentVector<SymbolTextAttributes> segments;
+        std::vector<PlacedSymbol> placedSymbols;
 
         optional<gl::VertexBuffer<SymbolLayoutVertex>> vertexBuffer;
+        optional<gl::VertexBuffer<SymbolDynamicLayoutAttributes::Vertex>> dynamicVertexBuffer;
         optional<gl::IndexBuffer<gl::Triangles>> indexBuffer;
     } text;
     
@@ -55,11 +75,14 @@ public:
     
     struct IconBuffer {
         gl::VertexVector<SymbolLayoutVertex> vertices;
+        gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex> dynamicVertices;
         gl::IndexVector<gl::Triangles> triangles;
         gl::SegmentVector<SymbolIconAttributes> segments;
+        std::vector<PlacedSymbol> placedSymbols;
         PremultipliedImage atlasImage;
 
         optional<gl::VertexBuffer<SymbolLayoutVertex>> vertexBuffer;
+        optional<gl::VertexBuffer<SymbolDynamicLayoutAttributes::Vertex>> dynamicVertexBuffer;
         optional<gl::IndexBuffer<gl::Triangles>> indexBuffer;
     } icon;
 
@@ -69,6 +92,7 @@ public:
         gl::SegmentVector<CollisionBoxAttributes> segments;
 
         optional<gl::VertexBuffer<CollisionBoxVertex>> vertexBuffer;
+        optional<gl::VertexBuffer<SymbolDynamicLayoutAttributes::Vertex>> dynamicVertexBuffer;
         optional<gl::IndexBuffer<gl::Lines>> indexBuffer;
     } collisionBox;
 };