[core] Switch from background to foreground placement

 - Background placement code now just generates static symbol buffers
 - Don't render GeometryTiles until their symbols are loaded. This is necessary for the CrossTileSymbolIndex to successfully prevent flicker.
 - SymbolInstances are transferred to SymbolBucket for use on foreground during collision detection
 - Symbols are sorted on foreground by sorting their index buffer but leaving vertex buffers intact (only works within one segment)
 - Vertical glyphs are generated at same time as horizontal glyphs. `reprojectLineLabels` chooses which one to use at render time and hides the other.
 - Icons are now always represented with a single collision box, even if they're placed along a line (this means their rotation alignment may be wrong, but the approach of representing them with multiple collision boxes wasn't very accurate either).
 - Generate vertices for new debug collision boxes and collision circles
 - Only add symbols within tile boundaries (reduces work, avoids double-draw)
 - Update symbol_projection.cpp to support line label projection calls from CollisionIndex.

1 files changed, 32 insertions, 2 deletions

diff --git a/src/mbgl/layout/symbol_projection.hpp b/src/mbgl/layout/symbol_projection.hpp
index 2652fe7ace..8535014f22 100644
--- a/src/mbgl/layout/symbol_projection.hpp
+++ b/src/mbgl/layout/symbol_projection.hpp
@@ -8,18 +8,48 @@ namespace mbgl {
 
     class TransformState;
     class RenderTile;
-    class FrameHistory;
     class SymbolSizeBinder;
     class PlacedSymbol;
     namespace style {
         class SymbolPropertyValues;
     } // end namespace style
+    
+    struct TileDistance {
+        TileDistance(float prevTileDistance_, float lastSegmentViewportDistance_)
+            : prevTileDistance(prevTileDistance_), lastSegmentViewportDistance(lastSegmentViewportDistance_)
+        {}
+        float prevTileDistance;
+        float lastSegmentViewportDistance;
+    };
+    
+    struct PlacedGlyph {
+        PlacedGlyph(Point<float> point_, float angle_, optional<TileDistance> tileDistance_)
+            : point(point_), angle(angle_), tileDistance(std::move(tileDistance_))
+        {}
+        Point<float> point;
+        float angle;
+        optional<TileDistance> tileDistance;
+    };
 
+    float evaluateSizeForFeature(const ZoomEvaluatedSize& zoomEvaluatedSize, const PlacedSymbol& placedSymbol);
     mat4 getLabelPlaneMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits);
     mat4 getGlCoordMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits);
+    
+    using PointAndCameraDistance = std::pair<Point<float>,float>;
+    PointAndCameraDistance project(const Point<float>& point, const mat4& matrix);
 
     void reprojectLineLabels(gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>&, const std::vector<PlacedSymbol>&,
             const mat4& posMatrix, const style::SymbolPropertyValues&,
-            const RenderTile&, const SymbolSizeBinder& sizeBinder, const TransformState&, const FrameHistory& frameHistory);
+            const RenderTile&, const SymbolSizeBinder& sizeBinder, const TransformState&);
+    
+    optional<std::pair<PlacedGlyph, PlacedGlyph>> placeFirstAndLastGlyph(const float fontScale,
+                                                            const float lineOffsetX,
+                                                            const float lineOffsetY,
+                                                            const bool flip,
+                                                            const Point<float>& anchorPoint,
+                                                            const Point<float>& tileAnchorPoint,
+                                                            const PlacedSymbol& symbol,
+                                                            const mat4& labelPlaneMatrix,
+                                                            const bool returnTileDistance);
 
 } // end namespace mbgl