Do not process partial tiles if no new resources have arrived

Partial tiles are now only processed again when there is a new resource
available. If we don't have new resources - like new glyphs - the end result
of the reparsing is the same, because no new SymbolBuckets would are created.

In my tests debugging with PowerTOP, this patch drops the CPU utilization
during the sampling period from 100ms/s to 40ms/s. The improvements on
slow connections (i.e. more time waiting for resources) are even more
noticeable.

4 files changed, 15 insertions, 4 deletions

diff --git a/src/mbgl/map/resource_loader.cpp b/src/mbgl/map/resource_loader.cpp
index 0f5c33abd2..46b7af9a28 100644
--- a/src/mbgl/map/resource_loader.cpp
+++ b/src/mbgl/map/resource_loader.cpp
@@ -85,11 +85,15 @@ void ResourceLoader::update(MapData& data,
 
     for (const auto& source : style_->sources) {
         source->update(data, transform, *style_, glyphAtlas, *glyphStore_,
-                       spriteAtlas, sprite_, texturePool);
+                       spriteAtlas, sprite_, texturePool, shouldReparsePartialTiles_);
     }
+
+    shouldReparsePartialTiles_ = false;
 }
 
 void ResourceLoader::onGlyphRangeLoaded() {
+    shouldReparsePartialTiles_ = true;
+
     emitTileDataChanged();
 }
 
@@ -102,6 +106,8 @@ void ResourceLoader::onTileLoaded() {
 }
 
 void ResourceLoader::onSpriteLoaded() {
+    shouldReparsePartialTiles_ = true;
+
     emitTileDataChanged();
 }
 
diff --git a/src/mbgl/map/resource_loader.hpp b/src/mbgl/map/resource_loader.hpp
index 6f63fe2260..cf73db5fa8 100644
--- a/src/mbgl/map/resource_loader.hpp
+++ b/src/mbgl/map/resource_loader.hpp
@@ -73,6 +73,8 @@ public:
 private:
     void emitTileDataChanged();
 
+    bool shouldReparsePartialTiles_ = false;
+
     std::string accessToken_;
     util::ptr<Sprite> sprite_;
 
diff --git a/src/mbgl/map/source.cpp b/src/mbgl/map/source.cpp
index 686b15c24e..501dde5c25 100644
--- a/src/mbgl/map/source.cpp
+++ b/src/mbgl/map/source.cpp
@@ -384,7 +384,8 @@ void Source::update(MapData& data,
                     GlyphStore& glyphStore,
                     SpriteAtlas& spriteAtlas,
                     util::ptr<Sprite> sprite,
-                    TexturePool& texturePool) {
+                    TexturePool& texturePool,
+                    bool shouldReparsePartialTiles) {
     if (!loaded || data.getAnimationTime() <= updated) {
         return;
     }
@@ -407,7 +408,8 @@ void Source::update(MapData& data,
 
         switch (state) {
         case TileData::State::partial:
-            handlePartialTile(id, style.workers);
+            if (shouldReparsePartialTiles)
+                handlePartialTile(id, style.workers);
             break;
         case TileData::State::invalid:
             state = addTile(data, transformState, style, glyphAtlas, glyphStore,
diff --git a/src/mbgl/map/source.hpp b/src/mbgl/map/source.hpp
index 15cc8a817b..d5f4f8b5d0 100644
--- a/src/mbgl/map/source.hpp
+++ b/src/mbgl/map/source.hpp
@@ -75,7 +75,8 @@ public:
                 GlyphStore&,
                 SpriteAtlas&,
                 util::ptr<Sprite>,
-                TexturePool&);
+                TexturePool&,
+                bool shouldReparsePartialTiles);
 
     void invalidateTiles(const std::vector<TileID>&);