move RenderPass check to the StyleLayer object

2 files changed, 36 insertions, 2 deletions

diff --git a/src/mbgl/style/style_layer.cpp b/src/mbgl/style/style_layer.cpp
index 5fc6af793c..dfd693dffa 100644
--- a/src/mbgl/style/style_layer.cpp
+++ b/src/mbgl/style/style_layer.cpp
@@ -28,6 +28,10 @@ bool StyleLayer::isVisible() const {
     }
 }
 
+bool StyleLayer::hasRenderPass(RenderPass pass) const {
+    return bool(passes & pass);
+}
+
 void StyleLayer::setClasses(const std::vector<std::string> &class_names, const TimePoint& now,
                             const PropertyTransition &defaultTransition) {
     // Stores all keys that we have already added transitions for.
@@ -260,6 +264,26 @@ void StyleLayer::updateProperties(float z, const TimePoint& now, ZoomHistory &zo
         case StyleLayerType::Background: applyStyleProperties<BackgroundProperties>(z, now, zoomHistory); break;
         default: properties.set<std::false_type>(); break;
     }
+
+    // Update the render passes when this layer is visible.
+    passes = RenderPass::None;
+    if (isVisible()) {
+        if (properties.is<FillProperties>()) {
+            const FillProperties &fillProperties = properties.get<FillProperties>();
+            const float alpha = fillProperties.fill_color[3] * fillProperties.opacity;
+
+            if (fillProperties.antialias) {
+                passes |= RenderPass::Translucent;
+            }
+            if (!fillProperties.image.from.empty() || alpha < 1.0f) {
+                passes |= RenderPass::Translucent;
+            } else {
+                passes |= RenderPass::Opaque;
+            }
+        } else {
+            passes |= RenderPass::Translucent;
+        }
+    }
 }
 
 bool StyleLayer::hasTransitions() const {
diff --git a/src/mbgl/style/style_layer.hpp b/src/mbgl/style/style_layer.hpp
index 56b8cb8f19..6d14e57e18 100644
--- a/src/mbgl/style/style_layer.hpp
+++ b/src/mbgl/style/style_layer.hpp
@@ -7,6 +7,8 @@
 #include <mbgl/style/applied_class_properties.hpp>
 #include <mbgl/style/zoom_history.hpp>
 
+#include <mbgl/renderer/render_pass.hpp>
+
 #include <mbgl/util/ptr.hpp>
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/chrono.hpp>
@@ -35,8 +37,9 @@ public:
     // Determines whether this layer is the background layer.
     bool isBackground() const;
 
-    // Checks whether the layer is currently visible at all.
-    bool isVisible() const;
+public:
+    // Checks whether this layer needs to be rendered in the given render pass.
+    bool hasRenderPass(RenderPass) const;
 
     // Updates the StyleProperties information in this layer by evaluating all
     // pending transitions and applied classes in order.
@@ -62,6 +65,9 @@ private:
     // Removes all expired style transitions.
     void cleanupAppliedStyleProperties(const TimePoint& now);
 
+    // Checks whether the layer is currently visible at all.
+    bool isVisible() const;
+
 public:
     // The name of this layer.
     const std::string id;
@@ -80,6 +86,10 @@ private:
     // optional transition times.
     std::map<PropertyKey, AppliedClassPropertyValues> appliedStyle;
 
+    // Stores what render passes this layer is currently enabled for. This depends on the
+    // evaluated StyleProperties object and is updated accordingly.
+    RenderPass passes = RenderPass::None;
+
 public:
     // Stores the evaluated, and cascaded styling information, specific to this
     // layer's type.