[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, 10 insertions, 8 deletions

diff --git a/src/mbgl/renderer/tile_pyramid.cpp b/src/mbgl/renderer/tile_pyramid.cpp
index 3e2311089d..f3ee787442 100644
--- a/src/mbgl/renderer/tile_pyramid.cpp
+++ b/src/mbgl/renderer/tile_pyramid.cpp
@@ -5,7 +5,6 @@
 #include <mbgl/renderer/tile_parameters.hpp>
 #include <mbgl/renderer/query.hpp>
 #include <mbgl/map/transform.hpp>
-#include <mbgl/text/placement_config.hpp>
 #include <mbgl/math/clamp.hpp>
 #include <mbgl/util/tile_cover.hpp>
 #include <mbgl/util/enum.hpp>
@@ -120,6 +119,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
     // use because they're still loading. In addition to that, we also need to retain all tiles that
     // we're actively using, e.g. as a replacement for tile that aren't loaded yet.
     std::set<OverscaledTileID> retain;
+    std::set<UnwrappedTileID> rendered;
 
     auto retainTileFn = [&](Tile& tile, TileNecessity necessity) -> void {
         if (retain.emplace(tile.id).second) {
@@ -150,6 +150,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
     };
     auto renderTileFn = [&](const UnwrappedTileID& tileID, Tile& tile) {
         renderTiles.emplace_back(tileID, tile);
+        rendered.emplace(tileID);
     };
 
     renderTiles.clear();
@@ -177,6 +178,13 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
         auto tilesIt = tiles.begin();
         auto retainIt = retain.begin();
         while (tilesIt != tiles.end()) {
+            auto renderedIt = rendered.find(tilesIt->first.toUnwrapped());
+            if (renderedIt == rendered.end()) {
+                // Since this tile isn't in the render set, crossTileIDs won't be kept
+                // updated by CrossTileSymbolIndex. We need to reset the stored crossTileIDs
+                // so they're not reused if/when this tile is re-added to the render set
+                tilesIt->second->resetCrossTileIDs();
+            }
             if (retainIt == retain.end() || tilesIt->first < *retainIt) {
                 if (!needsRelayout) {
                     tilesIt->second->setNecessity(TileNecessity::Optional);
@@ -193,13 +201,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
     }
 
     for (auto& pair : tiles) {
-        const PlacementConfig config { parameters.transformState.getAngle(),
-                                       parameters.transformState.getPitch(),
-                                       parameters.transformState.getCameraToCenterDistance(),
-                                       parameters.transformState.getCameraToTileDistance(pair.first.toUnwrapped()),
-                                       parameters.debugOptions & MapDebugOptions::Collision };
-
-        pair.second->setPlacementConfig(config);
+        pair.second->setShowCollisionBoxes(parameters.debugOptions & MapDebugOptions::Collision);
     }
 }