[core] Do not render symbol layers for pan tiles

src/mbgl/renderer/tile_pyramid.cpp

@@ -100,6 +100,15 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
  std::vector<UnwrappedTileID> idealTiles;
  std::vector<UnwrappedTileID> panTiles;
 
+ bool usePanLayers = true;
+ std::vector<Immutable<style::Layer::Impl>> panLayers;
+ panLayers.reserve(layers.size());
+ for (const auto& layer : layers) {
+ if (layer->type == LayerType::Symbol)
+ continue;
+ panLayers.emplace_back(layer);
+ }
+
  if (overscaledZoom >= zoomRange.min) {
  uint8_t idealZoom = std::min(zoomRange.max, overscaledZoom);
 
@@ -141,7 +150,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
  }
 
  if (needsRelayout) {
- tile.setLayers(layers);
+ tile.setLayers(usePanLayers ? panLayers : layers);
  }
  };
  auto getTileFn = [&](const OverscaledTileID& tileID) -> Tile* {
@@ -165,7 +174,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
  tile = createTile(tileID);
  if (tile) {
  tile->setObserver(observer);
- tile->setLayers(layers);
+ tile->setLayers(usePanLayers ? panLayers : layers);
  }
  }
  if (!tile) {
@@ -182,7 +191,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
  auto renderTileFn = [&](const UnwrappedTileID& tileID, Tile& tile) {
  renderTiles.emplace_back(tileID, tile);
  previouslyRenderedTiles.erase(tileID); // Still rendering this tile, no need for special fading logic.
- tile.markRenderedIdeal();
+ if (!usePanLayers) tile.markRenderedIdeal();
  };
 
  renderTiles.clear();
@@ -192,6 +201,7 @@ void TilePyramid::update(const std::vector<Immutable<style::Layer::Impl>>& layer
  panTiles, zoomRange, panZoom);
  }
 
+ usePanLayers = false;
  algorithm::updateRenderables(getTileFn, createTileFn, retainTileFn, renderTileFn,
  idealTiles, zoomRange, tileZoom);