[core] Add Source::startRender for parallelism with finishRender

src/mbgl/renderer/painter.cpp

@@ -161,11 +161,7 @@ void Painter::render(const Style& style, const FrameData& frame_, SpriteAtlas& a
         // Update all clipping IDs.
         algorithm::ClipIDGenerator generator;
         for (const auto& source : sources) {
-            if (source->type == SourceType::Vector || source->type == SourceType::GeoJSON ||
-                source->type == SourceType::Annotations) {
-                source->updateClipIDs(generator);
-            }
-            source->updateMatrices(projMatrix, state);
+            source->startRender(generator, projMatrix, state);
         }
 
         drawClippingMasks(generator.getStencils());

src/mbgl/style/source.cpp

@@ -22,6 +22,8 @@
 #include <mbgl/gl/debugging.hpp>
 
 #include <mbgl/algorithm/update_renderables.hpp>
+#include <mbgl/algorithm/generate_clip_ids.hpp>
+#include <mbgl/algorithm/generate_clip_ids_impl.hpp>
 
 #include <mapbox/geometry/envelope.hpp>
 
@@ -58,7 +60,15 @@ void Source::invalidateTiles() {
     cache.clear();
 }
 
-void Source::updateMatrices(const mat4 &projMatrix, const TransformState &transform) {
+void Source::startRender(algorithm::ClipIDGenerator& generator,
+                         const mat4& projMatrix,
+                         const TransformState& transform) {
+    if (type == SourceType::Vector ||
+        type == SourceType::GeoJSON ||
+        type == SourceType::Annotations) {
+        generator.update(renderTiles);
+    }
+
     for (auto& pair : renderTiles) {
         auto& tile = pair.second;
         transform.matrixFor(tile.matrix, tile.id);
@@ -66,7 +76,7 @@ void Source::updateMatrices(const mat4 &projMatrix, const TransformState &transf
     }
 }
 
-void Source::finishRender(Painter &painter) {
+void Source::finishRender(Painter& painter) {
     for (auto& pair : renderTiles) {
         auto& tile = pair.second;
         painter.renderTileDebug(tile);

src/mbgl/style/source.hpp

@@ -23,6 +23,10 @@ class TransformState;
 class RenderTile;
 struct ClipID;
 
+namespace algorithm {
+class ClipIDGenerator;
+} // namespace algorithm
+
 namespace style {
 
 class Style;
@@ -45,13 +49,10 @@ public:
     // new data available that a tile in the "partial" state might be interested at.
     bool update(const UpdateParameters&);
 
-    template <typename ClipIDGenerator>
-    void updateClipIDs(ClipIDGenerator& generator) {
-        generator.update(renderTiles);
-    }
-
-    void updateMatrices(const mat4 &projMatrix, const TransformState &transform);
-    void finishRender(Painter &painter);
+    void startRender(algorithm::ClipIDGenerator&,
+                     const mat4& projMatrix,
+                     const TransformState&);
+    void finishRender(Painter&);
 
     const std::map<UnwrappedTileID, RenderTile>& getRenderTiles() const;