[core] Reduce custom layer API to lowest common denominator

1 files changed, 39 insertions, 0 deletions

diff --git a/include/mbgl/style/types.hpp b/include/mbgl/style/types.hpp
index 95944ce18f..38915db7d8 100644
--- a/include/mbgl/style/types.hpp
+++ b/include/mbgl/style/types.hpp
@@ -189,6 +189,45 @@ MBGL_DEFINE_ENUM_CLASS(TextTransformTypeClass, TextTransformType, {
     { TextTransformType::Lowercase, "lowercase" },
 });
 
+/**
+ * Initialize any GL state needed by the custom layer. This method is called once, from the
+ * rendering thread, at a point when the GL context is active but before rendering for the
+ * first time.
+ *
+ * Resources that are acquired in this method must be released in the UninitializeFunction.
+ */
+using CustomLayerInitializeFunction = void (*)(void* context);
+
+/**
+ * Parameters that define the current camera position for a CustomLayerRenderFunction.
+ */
+struct CustomLayerRenderParameters {
+    double width;
+    double height;
+    double latitude;
+    double longitude;
+    double zoom;
+    double bearing;
+    double pitch;
+    double altitude;
+};
+
+/**
+ * Render the layer. This method is called once per frame. The implementation should not make
+ * any assumptions about the GL state (other than that the correct context is active). It may
+ * make changes to the state, and is not required to reset values such as the depth mask, stencil
+ * mask, and corresponding test flags to their original values.
+ */
+using CustomLayerRenderFunction = void (*)(void* context, const CustomLayerRenderParameters&);
+
+/**
+ * Destroy any GL state needed by the custom layer, and deallocate context, if necessary. This
+ * method is called once, from the rendering thread, at a point when the GL context is active.
+ *
+ * Note that it may be called even when the InitializeFunction has not been called.
+ */
+using CustomLayerDeinitializeFunction = void (*)(void* context);
+
 } // namespace mbgl
 
 #endif