[core] Introduce mbgl::RendererState

cmake/core-files.txt

@@ -180,6 +180,7 @@ include/mbgl/renderer/renderer.hpp
 include/mbgl/renderer/renderer_backend.hpp
 include/mbgl/renderer/renderer_frontend.hpp
 include/mbgl/renderer/renderer_observer.hpp
+include/mbgl/renderer/renderer_state.hpp
 src/mbgl/renderer/backend_scope.cpp
 src/mbgl/renderer/bucket.hpp
 src/mbgl/renderer/bucket_parameters.cpp
@@ -216,6 +217,7 @@ src/mbgl/renderer/renderer.cpp
 src/mbgl/renderer/renderer_backend.cpp
 src/mbgl/renderer/renderer_impl.cpp
 src/mbgl/renderer/renderer_impl.hpp
+src/mbgl/renderer/renderer_state.cpp
 src/mbgl/renderer/style_diff.cpp
 src/mbgl/renderer/style_diff.hpp
 src/mbgl/renderer/tile_mask.hpp

include/mbgl/renderer/renderer_state.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <mbgl/map/camera.hpp>
+#include <mbgl/util/geo.hpp>
+
+namespace mbgl {
+
+class UpdateParameters;
+
+/**
+ * RendererState acts as a Memento-like object that is able to extract data out of UpdateParameters (an opaque object
+ * from the public API perspective).
+ */
+class RendererState {
+public:
+
+    // Obtains a CameraOptions out of a given UpdateParameters object.
+    static CameraOptions getCameraOptions(UpdateParameters&, const EdgeInsets& = {});
+
+};
+
+} // namespace mbgl

platform/default/mbgl/gl/headless_frontend.cpp

@@ -1,5 +1,6 @@
 #include <mbgl/gl/headless_frontend.hpp>
 #include <mbgl/renderer/renderer.hpp>
+#include <mbgl/renderer/renderer_state.hpp>
 #include <mbgl/renderer/update_parameters.hpp>
 #include <mbgl/map/map.hpp>
 #include <mbgl/map/transform_state.hpp>

src/mbgl/map/transform_state.hpp

@@ -20,6 +20,7 @@ class UnwrappedTileID;
 
 class TransformState {
     friend class Transform;
+    friend class RendererState;
 
 public:
     TransformState(ConstrainMode = ConstrainMode::HeightOnly, ViewportMode = ViewportMode::Default);

src/mbgl/renderer/renderer_state.cpp

@@ -0,0 +1,10 @@
+#include <mbgl/renderer/renderer_state.hpp>
+#include <mbgl/renderer/update_parameters.hpp>
+
+namespace mbgl {
+
+CameraOptions RendererState::getCameraOptions(UpdateParameters& updateParameters, const EdgeInsets& padding) {
+    return updateParameters.transformState.getCameraOptions(padding);
+}
+
+} // namespace mbgl

test/map/map.test.cpp

@@ -49,6 +49,34 @@ public:
     }
 };
 
+TEST(Map, RendererState) {
+    MapTest<> test;
+
+    // Map hasn't notified the frontend about an update yet.
+    CameraOptions nullOptions;
+    ASSERT_EQ(test.frontend.getCameraOptions(), nullOptions);
+
+    LatLng coordinate { 1, 1 };
+    double zoom = 12.0;
+    double pitchInDegrees = 45.0;
+    double bearingInDegrees = 30.0;
+
+    test.map.getStyle().loadJSON(util::read_file("test/fixtures/api/empty.json"));
+    test.map.setLatLngZoom(coordinate, zoom);
+    test.map.setPitch(pitchInDegrees);
+    test.map.setBearing(bearingInDegrees);
+
+    test.runLoop.runOnce();
+    test.frontend.render(test.map);
+
+    const CameraOptions& options = test.frontend.getCameraOptions();
+    EXPECT_NEAR(options.center->latitude(), coordinate.latitude(), 1e-7);
+    EXPECT_NEAR(options.center->longitude(), coordinate.longitude(), 1e-7);
+    ASSERT_DOUBLE_EQ(*options.zoom, zoom);
+    ASSERT_DOUBLE_EQ(*options.pitch, pitchInDegrees);
+    EXPECT_NEAR(*options.angle, bearingInDegrees, 1e-7);
+}
+
 TEST(Map, LatLngBehavior) {
     MapTest<> test;