add prepare() function

1 files changed, 21 insertions, 0 deletions

diff --git a/src/mbgl/renderer/bucket.hpp b/src/mbgl/renderer/bucket.hpp
index 2ea73f9b97..282a6aa367 100644
--- a/src/mbgl/renderer/bucket.hpp
+++ b/src/mbgl/renderer/bucket.hpp
@@ -10,11 +10,32 @@ class Painter;
 class StyleLayer;
 class TileID;
 
+enum class RenderPass : uint8_t {
+    Prepare = 1 << 0,
+    Opaque = 1 << 1,
+    Translucent = 1 << 2,
+};
+
 class Bucket : private util::noncopyable {
 public:
+    // As long as this bucket has a Prepare render pass, this function is getting called. Typically,
+    // this only happens once when the bucket is being rendered for the first time.
+    virtual void prepare() = 0;
+
+    // Every time this bucket is getting rendered, this function is called. This happens either
+    // once or twice (for Opaque and Transparent render passes).
     virtual void render(Painter&, const StyleLayer&, const TileID&, const mat4&) = 0;
+
     virtual ~Bucket() {}
 
+    inline bool hasRenderPass(RenderPass pass) const {
+        return static_cast<std::underlying_type<RenderPass>::type>(renderPass) &
+               static_cast<std::underlying_type<RenderPass>::type>(pass);
+    }
+
+protected:
+    RenderPass renderPass = RenderPass::Prepare;
+
 };
 
 }