From 15f73a06f2048d4b5f0481d54a79f3f349187b11 Mon Sep 17 00:00:00 2001
From: Alexander Shalamov <alexander.shalamov@mapbox.com>
Date: Sat, 21 Mar 2020 21:55:22 +0200
Subject: [core] Add setMaxOverscaleFactorForParentTiles

---
 src/mbgl/algorithm/update_renderables.hpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'src/mbgl/algorithm')

diff --git a/src/mbgl/algorithm/update_renderables.hpp b/src/mbgl/algorithm/update_renderables.hpp
index 57cd4f41ec..316ada8269 100644
--- a/src/mbgl/algorithm/update_renderables.hpp
+++ b/src/mbgl/algorithm/update_renderables.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/tile/tile_id.hpp>
 #include <mbgl/tile/tile_necessity.hpp>
+#include <mbgl/util/optional.hpp>
 #include <mbgl/util/range.hpp>
 
 #include <unordered_set>
@@ -20,7 +21,8 @@ void updateRenderables(GetTileFn getTile,
                        RenderTileFn renderTile,
                        const IdealTileIDs& idealTileIDs,
                        const Range<uint8_t>& zoomRange,
-                       const uint8_t dataTileZoom) {
+                       const uint8_t dataTileZoom,
+                       const optional<uint8_t>& maxParentOverscaleFactor = nullopt) {
     std::unordered_set<OverscaledTileID> checked;
     bool covered;
     int32_t overscaledZ;
@@ -86,6 +88,11 @@ void updateRenderables(GetTileFn getTile,
                 for (overscaledZ = dataTileZoom - 1; overscaledZ >= zoomRange.min; --overscaledZ) {
                     const auto parentDataTileID = idealDataTileID.scaledTo(overscaledZ);
 
+                    // Request / render parent tile only if it's overscale factor is less than defined maximum.
+                    if (maxParentOverscaleFactor && (dataTileZoom - overscaledZ) > *maxParentOverscaleFactor) {
+                        break;
+                    }
+
                     if (checked.find(parentDataTileID) != checked.end()) {
                         // Break parent tile ascent, this route has been checked by another child
                         // tile before.
-- 
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