[core] Rework attribute binding (again)

These changes are necessary for programs whose set of active attributes is not fixed at compile time by a template parameter pack, but rather varies based on the generated shader text at runtime. In such cases, the attribute location of a given named attribute may vary between instances of the same Program.

Previously, attribute bindings were implicitly associated with a location based on template parameter order, and -1 was used to indicate an inactive attribute. This left us unable to disable the appropriate attribute when it went from active to inactive. Now, the state tracker for bindings explicitly associates locations and state, and an empty optional is used to indicate an inactive attribute.

In addition, a gl::VertexArray class is now exposed, allowing more flexibility in the relationship between Programs, Segments, and attribute bindings. In this commit, that relationship does not change, but the subsequent commit adjusts it to match gl-js, reduce rebinds, and work around buggy VAO implementations.

VertexArray uses a pimpl idiom in order to support implementations that lack the VAO extension. In that case, all VertexArrays share global binding state, reflecting the platform reality in the absence of VAOs, while still providing a uniform API.

14 files changed, 226 insertions, 245 deletions

diff --git a/src/mbgl/gl/attribute.cpp b/src/mbgl/gl/attribute.cpp
index 5583cfd916..bb5b2ddc34 100644
--- a/src/mbgl/gl/attribute.cpp
+++ b/src/mbgl/gl/attribute.cpp
@@ -1,16 +1,14 @@
 #include <mbgl/gl/attribute.hpp>
-#include <mbgl/gl/context.hpp>
 #include <mbgl/gl/gl.hpp>
 
-#include <cstring>
-
 namespace mbgl {
 namespace gl {
 
-AttributeLocation bindAttributeLocation(ProgramID id, AttributeLocation location, const char* name) {
-    assert(location < 8);
+void bindAttributeLocation(ProgramID id, AttributeLocation location, const char* name) {
+    if (location >= MAX_ATTRIBUTES) {
+        throw gl::Error("too many vertex attributes");
+    }
     MBGL_CHECK_ERROR(glBindAttribLocation(id, location, name));
-    return location;
 }
 
 std::set<std::string> getActiveAttributes(ProgramID id) {
@@ -37,58 +35,5 @@ std::set<std::string> getActiveAttributes(ProgramID id) {
     return activeAttributes;
 }
 
-void DisabledAttribute::bind(Context&, AttributeLocation location, std::size_t) const {
-    MBGL_CHECK_ERROR(glDisableVertexAttribArray(location));
-}
-
-template <class T>
-constexpr DataType DataTypeOf() {
-    return std::is_same<T,   int8_t>::value ? DataType::Byte :
-           std::is_same<T,  uint8_t>::value ? DataType::UnsignedByte :
-           std::is_same<T,  int16_t>::value ? DataType::Short :
-           std::is_same<T, uint16_t>::value ? DataType::UnsignedShort :
-           std::is_same<T,  int32_t>::value ? DataType::Integer :
-           std::is_same<T, uint32_t>::value ? DataType::UnsignedInteger :
-           std::is_same<T,    float>::value ? DataType::Float : static_cast<DataType>(0);
-}
-
-template <class T, std::size_t N>
-void AttributeBinding<T, N>::bind(Context& context, AttributeLocation location, std::size_t vertexOffset) const {
-    // FillProgram will attempt to bind at location -1 because it includes
-    // a fill-outline-color paint property but does not use it or have an
-    // a_outline_color shader attribute - in this case, we have nothing to bind.
-    if (location == -1) return;
-
-    context.vertexBuffer = vertexBuffer;
-    MBGL_CHECK_ERROR(glEnableVertexAttribArray(location));
-    MBGL_CHECK_ERROR(glVertexAttribPointer(
-        location,
-        static_cast<GLint>(attributeSize),
-        static_cast<GLenum>(DataTypeOf<T>()),
-        static_cast<GLboolean>(false),
-        static_cast<GLsizei>(vertexSize),
-        reinterpret_cast<GLvoid*>(attributeOffset + (vertexSize * vertexOffset))));
-}
-
-template class AttributeBinding<uint8_t, 1>;
-template class AttributeBinding<uint8_t, 2>;
-template class AttributeBinding<uint8_t, 3>;
-template class AttributeBinding<uint8_t, 4>;
-
-template class AttributeBinding<uint16_t, 1>;
-template class AttributeBinding<uint16_t, 2>;
-template class AttributeBinding<uint16_t, 3>;
-template class AttributeBinding<uint16_t, 4>;
-
-template class AttributeBinding<int16_t, 1>;
-template class AttributeBinding<int16_t, 2>;
-template class AttributeBinding<int16_t, 3>;
-template class AttributeBinding<int16_t, 4>;
-
-template class AttributeBinding<float, 1>;
-template class AttributeBinding<float, 2>;
-template class AttributeBinding<float, 3>;
-template class AttributeBinding<float, 4>;
-
 } // namespace gl
 } // namespace mbgl
diff --git a/src/mbgl/gl/attribute.hpp b/src/mbgl/gl/attribute.hpp
index bc02b54bd2..1f60c8c980 100644
--- a/src/mbgl/gl/attribute.hpp
+++ b/src/mbgl/gl/attribute.hpp
@@ -1,59 +1,51 @@
 #pragma once
 
 #include <mbgl/gl/types.hpp>
-#include <mbgl/gl/segment.hpp>
+#include <mbgl/gl/vertex_buffer.hpp>
 #include <mbgl/util/ignore.hpp>
 #include <mbgl/util/indexed_tuple.hpp>
-#include <mbgl/util/variant.hpp>
+#include <mbgl/util/optional.hpp>
 
 #include <cstddef>
 #include <vector>
 #include <set>
 #include <functional>
+#include <string>
+#include <array>
 
 namespace mbgl {
 namespace gl {
 
-class DisabledAttribute {
-public:
-    void bind(Context&, AttributeLocation, std::size_t vertexOffset) const;
+static constexpr std::size_t MAX_ATTRIBUTES = 8;
 
-    friend bool operator==(const DisabledAttribute&,
-                           const DisabledAttribute&) {
-        return true;
-    }
-};
+template <class> struct DataTypeOf;
+template <> struct DataTypeOf< int8_t>  : std::integral_constant<DataType, DataType::Byte> {};
+template <> struct DataTypeOf<uint8_t>  : std::integral_constant<DataType, DataType::UnsignedByte> {};
+template <> struct DataTypeOf< int16_t> : std::integral_constant<DataType, DataType::Short> {};
+template <> struct DataTypeOf<uint16_t> : std::integral_constant<DataType, DataType::UnsignedShort> {};
+template <> struct DataTypeOf< int32_t> : std::integral_constant<DataType, DataType::Integer> {};
+template <> struct DataTypeOf<uint32_t> : std::integral_constant<DataType, DataType::UnsignedInteger> {};
+template <> struct DataTypeOf<float>    : std::integral_constant<DataType, DataType::Float> {};
 
-template <class T, std::size_t N>
 class AttributeBinding {
 public:
-    AttributeBinding(BufferID vertexBuffer_,
-                     std::size_t vertexSize_,
-                     std::size_t attributeOffset_,
-                     std::size_t attributeSize_ = N)
-        : vertexBuffer(vertexBuffer_),
-          vertexSize(vertexSize_),
-          attributeOffset(attributeOffset_),
-          attributeSize(attributeSize_)
-        {}
-
-    void bind(Context&, AttributeLocation, std::size_t vertexOffset) const;
+    DataType attributeType;
+    std::size_t attributeSize;
+    std::size_t attributeOffset;
+
+    BufferID vertexBuffer;
+    std::size_t vertexSize;
+    std::size_t vertexOffset;
 
     friend bool operator==(const AttributeBinding& lhs,
                            const AttributeBinding& rhs) {
-        return lhs.vertexBuffer == rhs.vertexBuffer
-            && lhs.vertexSize == rhs.vertexSize
-            && lhs.attributeOffset == rhs.attributeOffset
-            && lhs.attributeSize == rhs.attributeSize;
+        return std::tie(lhs.attributeType, lhs.attributeSize, lhs.attributeOffset, lhs.vertexBuffer, lhs.vertexSize, lhs.vertexOffset)
+            == std::tie(rhs.attributeType, rhs.attributeSize, rhs.attributeOffset, rhs.vertexBuffer, rhs.vertexSize, rhs.vertexOffset);
     }
-
-private:
-    BufferID vertexBuffer;
-    std::size_t vertexSize;
-    std::size_t attributeOffset;
-    std::size_t attributeSize;
 };
 
+using AttributeBindingArray = std::array<optional<AttributeBinding>, MAX_ATTRIBUTES>;
+
 /*
     gl::Attribute<T,N> manages the binding of a vertex buffer to a GL program attribute.
       - T is the underlying primitive type (exposed as Attribute<T,N>::ValueType)
@@ -67,10 +59,7 @@ public:
     using Value = std::array<T, N>;
 
     using Location = AttributeLocation;
-
-    using Binding = variant<
-        DisabledAttribute,
-        AttributeBinding<T, N>>;
+    using Binding = AttributeBinding;
 
     /*
         Create a binding for this attribute.  The `attributeSize` parameter may be used to
@@ -82,28 +71,24 @@ public:
                            std::size_t attributeIndex,
                            std::size_t attributeSize = N) {
         static_assert(std::is_standard_layout<Vertex>::value, "vertex type must use standard layout");
-        return AttributeBinding<T, N> {
+        return AttributeBinding {
+            DataTypeOf<T>::value,
+            attributeSize,
+            Vertex::attributeOffsets[attributeIndex],
             buffer.buffer,
             sizeof(Vertex),
-            Vertex::attributeOffsets[attributeIndex],
-            attributeSize
+            0,
         };
     }
 
-    static void bind(Context& context,
-                     const Location& location,
-                     Binding& oldBinding,
-                     const Binding& newBinding,
-                     std::size_t vertexOffset) {
-        if (oldBinding == newBinding) {
-            return;
+    static optional<Binding> offsetBinding(const optional<Binding>& binding, std::size_t vertexOffset) {
+        if (binding) {
+            AttributeBinding result = *binding;
+            result.vertexOffset = vertexOffset;
+            return result;
+        } else {
+            return binding;
         }
-
-        Binding::visit(newBinding, [&] (const auto& binding) {
-            binding.bind(context, location, vertexOffset);
-        });
-
-        oldBinding = newBinding;
     }
 };
 
@@ -223,7 +208,7 @@ const std::size_t Vertex<A1, A2, A3, A4, A5>::attributeOffsets[5] = {
 
 } // namespace detail
 
-AttributeLocation bindAttributeLocation(ProgramID, AttributeLocation, const char * name);
+void bindAttributeLocation(ProgramID, AttributeLocation, const char * name);
 std::set<std::string> getActiveAttributes(ProgramID);
 
 template <class... As>
@@ -232,10 +217,10 @@ public:
     using Types = TypeList<As...>;
     using Locations = IndexedTuple<
         TypeList<As...>,
-        TypeList<typename As::Type::Location...>>;
+        TypeList<optional<typename As::Type::Location>...>>;
     using Bindings = IndexedTuple<
         TypeList<As...>,
-        TypeList<typename As::Type::Binding...>>;
+        TypeList<optional<typename As::Type::Binding>...>>;
     using NamedLocations = std::vector<std::pair<const std::string, AttributeLocation>>;
 
     using Vertex = detail::Vertex<typename As::Type...>;
@@ -243,13 +228,17 @@ public:
     static Locations bindLocations(const ProgramID& id) {
         std::set<std::string> activeAttributes = getActiveAttributes(id);
 
-        AttributeLocation location = -1;
-        auto bindAndIncrement = [&](const char* name) {
-            location++;
-            return bindAttributeLocation(id, location, name);
+        AttributeLocation location = 0;
+        auto maybeBindLocation = [&](const char* name) -> optional<AttributeLocation> {
+            if (activeAttributes.count(name)) {
+                bindAttributeLocation(id, location, name);
+                return location++;
+            } else {
+                return {};
+            }
         };
-        return Locations{ (activeAttributes.count(As::name()) ? bindAndIncrement(As::name())
-                                                              : -1)... };
+
+        return Locations { maybeBindLocation(As::name())... };
     }
 
     template <class Program>
@@ -258,7 +247,17 @@ public:
     }
 
     static NamedLocations getNamedLocations(const Locations& locations) {
-        return NamedLocations{ { As::name(), locations.template get<As>() }... };
+        NamedLocations result;
+
+        auto maybeAddLocation = [&] (const std::string& name, const optional<AttributeLocation>& location) {
+            if (location) {
+                result.emplace_back(name, *location);
+            }
+        };
+
+        util::ignore({ (maybeAddLocation(As::name(), locations.template get<As>()), 0)... });
+
+        return result;
     }
 
     template <class DrawMode>
@@ -266,16 +265,23 @@ public:
         return Bindings { As::Type::binding(buffer, TypeIndex<As, As...>::value)... };
     }
 
-    static void bind(Context& context,
-                     const Locations& locations,
-                     Bindings& oldBindings,
-                     const Bindings& newBindings,
-                     std::size_t vertexOffset) {
-        util::ignore({ (As::Type::bind(context,
-                                       locations.template get<As>(),
-                                       oldBindings.template get<As>(),
-                                       newBindings.template get<As>(),
-                                       vertexOffset), 0)... });
+    static Bindings offsetBindings(const Bindings& bindings, std::size_t vertexOffset) {
+        return Bindings { As::Type::offsetBinding(bindings.template get<As>(), vertexOffset)... };
+    }
+
+    static AttributeBindingArray toBindingArray(const Locations& locations, const Bindings& bindings) {
+        AttributeBindingArray result;
+
+        auto maybeAddBinding = [&] (const optional<AttributeLocation>& location,
+                                    const optional<AttributeBinding>& binding) {
+            if (location) {
+                result.at(*location) = binding;
+            }
+        };
+
+        util::ignore({ (maybeAddBinding(locations.template get<As>(), bindings.template get<As>()), 0)... });
+
+        return result;
     }
 };
 
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 86ca9c0607..f7d210d52e 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -229,8 +229,8 @@ UniqueBuffer Context::createIndexBuffer(const void* data, std::size_t size) {
     BufferID id = 0;
     MBGL_CHECK_ERROR(glGenBuffers(1, &id));
     UniqueBuffer result { std::move(id), { this } };
-    vertexArrayObject = 0;
-    elementBuffer = result;
+    bindVertexArray = 0;
+    globalVertexArrayState.indexBuffer = result;
     MBGL_CHECK_ERROR(glBufferData(GL_ELEMENT_ARRAY_BUFFER, size, data, GL_STATIC_DRAW));
     return result;
 }
@@ -281,11 +281,16 @@ optional<std::pair<BinaryProgramFormat, std::string>> Context::getBinaryProgram(
 }
 #endif
 
-UniqueVertexArray Context::createVertexArray() {
-    assert(supportsVertexArrays());
-    VertexArrayID id = 0;
-    MBGL_CHECK_ERROR(vertexArray->genVertexArrays(1, &id));
-    return UniqueVertexArray(std::move(id), { this });
+VertexArray Context::createVertexArray() {
+    if (supportsVertexArrays()) {
+        VertexArrayID id = 0;
+        MBGL_CHECK_ERROR(vertexArray->genVertexArrays(1, &id));
+        return { std::make_unique<VertexArrayState>(UniqueVertexArray(std::move(id), { this }), *this) };
+    } else {
+        // On GL implementations which do not support vertex arrays, attribute bindings are global state.
+        // So return a VertexArray which shares our global state tracking and whose deleter is a no-op.
+        return { UniqueVertexArrayState(&globalVertexArrayState, [] (VertexArrayState*) {}) };
+    }
 }
 
 UniqueFramebuffer Context::createFramebuffer() {
@@ -553,8 +558,8 @@ void Context::setDirtyState() {
        tex.setDirty();
     }
     vertexBuffer.setDirty();
-    elementBuffer.setDirty();
-    vertexArrayObject.setDirty();
+    bindVertexArray.setDirty();
+    globalVertexArrayState.setDirty();
 }
 
 void Context::clear(optional<mbgl::Color> color,
@@ -673,8 +678,8 @@ void Context::performCleanup() {
         for (const auto id : abandonedBuffers) {
             if (vertexBuffer == id) {
                 vertexBuffer.setDirty();
-            } else if (elementBuffer == id) {
-                elementBuffer.setDirty();
+            } else if (globalVertexArrayState.indexBuffer == id) {
+                globalVertexArrayState.indexBuffer.setDirty();
             }
         }
         MBGL_CHECK_ERROR(glDeleteBuffers(int(abandonedBuffers.size()), abandonedBuffers.data()));
@@ -694,8 +699,8 @@ void Context::performCleanup() {
     if (!abandonedVertexArrays.empty()) {
         assert(supportsVertexArrays());
         for (const auto id : abandonedVertexArrays) {
-            if (vertexArrayObject == id) {
-                vertexArrayObject.setDirty();
+            if (bindVertexArray == id) {
+                bindVertexArray.setDirty();
             }
         }
         MBGL_CHECK_ERROR(vertexArray->deleteVertexArrays(int(abandonedVertexArrays.size()),
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 2e594618d2..0dd67d2ed7 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -9,6 +9,7 @@
 #include <mbgl/gl/framebuffer.hpp>
 #include <mbgl/gl/vertex_buffer.hpp>
 #include <mbgl/gl/index_buffer.hpp>
+#include <mbgl/gl/vertex_array.hpp>
 #include <mbgl/gl/types.hpp>
 #include <mbgl/gl/draw_mode.hpp>
 #include <mbgl/gl/depth_mode.hpp>
@@ -53,9 +54,7 @@ public:
     void verifyProgramLinkage(ProgramID);
     void linkProgram(ProgramID);
     UniqueTexture createTexture();
-
-    bool supportsVertexArrays() const;
-    UniqueVertexArray createVertexArray();
+    VertexArray createVertexArray();
 
 #if MBGL_HAS_BINARY_PROGRAMS
     bool supportsProgramBinaries() const;
@@ -207,10 +206,11 @@ public:
     State<value::Viewport> viewport;
     State<value::ScissorTest> scissorTest;
     std::array<State<value::BindTexture>, 2> texture;
-    State<value::BindVertexArray, const Context&> vertexArrayObject { *this };
     State<value::Program> program;
     State<value::BindVertexBuffer> vertexBuffer;
-    State<value::BindElementBuffer> elementBuffer;
+
+    State<value::BindVertexArray, const Context&> bindVertexArray { *this };
+    VertexArrayState globalVertexArrayState { UniqueVertexArray(0, { this }), *this };
 
     State<value::PixelStorePack> pixelStorePack;
     State<value::PixelStoreUnpack> pixelStoreUnpack;
@@ -257,6 +257,8 @@ private:
     void drawPixels(Size size, const void* data, TextureFormat);
 #endif // MBGL_USE_GLES2
 
+    bool supportsVertexArrays() const;
+
     friend detail::ProgramDeleter;
     friend detail::ShaderDeleter;
     friend detail::BufferDeleter;
diff --git a/src/mbgl/gl/object.cpp b/src/mbgl/gl/object.cpp
index e2d476e0c0..2c5f1bca1f 100644
--- a/src/mbgl/gl/object.cpp
+++ b/src/mbgl/gl/object.cpp
@@ -33,7 +33,9 @@ void TextureDeleter::operator()(TextureID id) const {
 
 void VertexArrayDeleter::operator()(VertexArrayID id) const {
     assert(context);
-    context->abandonedVertexArrays.push_back(id);
+    if (id != 0) {
+        context->abandonedVertexArrays.push_back(id);
+    }
 }
 
 void FramebufferDeleter::operator()(FramebufferID id) const {
diff --git a/src/mbgl/gl/program.hpp b/src/mbgl/gl/program.hpp
index ce2b5a335b..9d8b0a5b04 100644
--- a/src/mbgl/gl/program.hpp
+++ b/src/mbgl/gl/program.hpp
@@ -5,6 +5,7 @@
 #include <mbgl/gl/context.hpp>
 #include <mbgl/gl/vertex_buffer.hpp>
 #include <mbgl/gl/index_buffer.hpp>
+#include <mbgl/gl/vertex_array.hpp>
 #include <mbgl/gl/attribute.hpp>
 #include <mbgl/gl/uniform.hpp>
 
@@ -116,10 +117,12 @@ public:
               DepthMode depthMode,
               StencilMode stencilMode,
               ColorMode colorMode,
-              UniformValues&& uniformValues,
-              AttributeBindings&& attributeBindings,
+              const UniformValues& uniformValues,
+              VertexArray& vertexArray,
+              const AttributeBindings& attributeBindings,
               const IndexBuffer<DrawMode>& indexBuffer,
-              const SegmentVector<Attributes>& segments) {
+              std::size_t indexOffset,
+              std::size_t indexLength) {
         static_assert(std::is_same<Primitive, typename DrawMode::Primitive>::value, "incompatible draw mode");
 
         context.setDrawMode(drawMode);
@@ -129,18 +132,15 @@ public:
 
         context.program = program;
 
-        Uniforms::bind(uniformsState, std::move(uniformValues));
+        Uniforms::bind(uniformsState, uniformValues);
 
-        for (const auto& segment : segments) {
-            segment.bind(context,
-                         indexBuffer.buffer,
-                         attributeLocations,
-                         attributeBindings);
+        vertexArray.bind(context,
+                        indexBuffer.buffer,
+                        Attributes::toBindingArray(attributeLocations, attributeBindings));
 
-            context.draw(drawMode.primitiveType,
-                         segment.indexOffset,
-                         segment.indexLength);
-        }
+        context.draw(drawMode.primitiveType,
+                     indexOffset,
+                     indexLength);
     }
 
 private:
diff --git a/src/mbgl/gl/segment.cpp b/src/mbgl/gl/segment.cpp
deleted file mode 100644
index aabdc83cd4..0000000000
--- a/src/mbgl/gl/segment.cpp
+++ /dev/null
@@ -1,7 +0,0 @@
-#include <mbgl/gl/segment.hpp>
-
-namespace mbgl {
-namespace gl {
-
-} // namespace gl
-} // namespace mbgl
diff --git a/src/mbgl/gl/segment.hpp b/src/mbgl/gl/segment.hpp
deleted file mode 100644
index fe0658bf8e..0000000000
--- a/src/mbgl/gl/segment.hpp
+++ /dev/null
@@ -1,73 +0,0 @@
-#pragma once
-
-#include <mbgl/gl/context.hpp>
-#include <mbgl/gl/vertex_buffer.hpp>
-#include <mbgl/util/optional.hpp>
-#include <mbgl/util/logging.hpp>
-
-#include <cstddef>
-#include <vector>
-
-namespace mbgl {
-namespace gl {
-
-template <class Attributes>
-class Segment {
-public:
-    Segment(std::size_t vertexOffset_,
-            std::size_t indexOffset_,
-            std::size_t vertexLength_ = 0,
-            std::size_t indexLength_ = 0)
-        : vertexOffset(vertexOffset_),
-          indexOffset(indexOffset_),
-          vertexLength(vertexLength_),
-          indexLength(indexLength_) {}
-
-    const std::size_t vertexOffset;
-    const std::size_t indexOffset;
-
-    std::size_t vertexLength;
-    std::size_t indexLength;
-
-    void bind(Context& context,
-              BufferID indexBuffer_,
-              const typename Attributes::Locations& attributeLocations,
-              const typename Attributes::Bindings& attributeBindings_) const {
-        if (context.supportsVertexArrays()) {
-            if (!vao) {
-                vao = context.createVertexArray();
-                context.vertexBuffer.setDirty();
-            }
-            context.vertexArrayObject = *vao;
-            if (indexBuffer != indexBuffer_) {
-                indexBuffer = indexBuffer_;
-                context.elementBuffer.setDirty();
-                context.elementBuffer = indexBuffer_;
-            }
-        } else {
-            // No VAO support. Force attributes to be rebound.
-            context.elementBuffer = indexBuffer_;
-            attributeBindings = {};
-        }
-
-        Attributes::bind(context,
-                         attributeLocations,
-                         attributeBindings,
-                         attributeBindings_,
-                         vertexOffset);
-    }
-
-private:
-    mutable optional<UniqueVertexArray> vao;
-    mutable optional<BufferID> indexBuffer;
-    mutable typename Attributes::Bindings attributeBindings;
-};
-
-template <class Attributes>
-class SegmentVector : public std::vector<Segment<Attributes>> {
-public:
-    SegmentVector() = default;
-};
-
-} // namespace gl
-} // namespace mbgl
diff --git a/src/mbgl/gl/types.hpp b/src/mbgl/gl/types.hpp
index 1fce878c6f..058bc226b8 100644
--- a/src/mbgl/gl/types.hpp
+++ b/src/mbgl/gl/types.hpp
@@ -15,7 +15,7 @@ using VertexArrayID = uint32_t;
 using FramebufferID = uint32_t;
 using RenderbufferID = uint32_t;
 
-using AttributeLocation = int32_t;
+using AttributeLocation = uint32_t;
 using UniformLocation = int32_t;
 using TextureUnit = uint8_t;
 
diff --git a/src/mbgl/gl/uniform.hpp b/src/mbgl/gl/uniform.hpp
index 4ed2419764..5a78068fc8 100644
--- a/src/mbgl/gl/uniform.hpp
+++ b/src/mbgl/gl/uniform.hpp
@@ -115,7 +115,7 @@ public:
         return NamedLocations{ { Us::name(), state.template get<Us>().location }... };
     }
 
-    static void bind(State& state, Values&& values) {
+    static void bind(State& state, const Values& values) {
         util::ignore({ (state.template get<Us>() = values.template get<Us>(), 0)... });
     }
 };
diff --git a/src/mbgl/gl/value.cpp b/src/mbgl/gl/value.cpp
index 2b825fb2bd..89014fe6bc 100644
--- a/src/mbgl/gl/value.cpp
+++ b/src/mbgl/gl/value.cpp
@@ -365,6 +365,24 @@ BindVertexArray::Type BindVertexArray::Get(const Context& context) {
     return binding;
 }
 
+const optional<AttributeBinding> VertexAttribute::Default {};
+
+void VertexAttribute::Set(const optional<AttributeBinding>& binding, Context& context, AttributeLocation location) {
+    if (binding) {
+        context.vertexBuffer = binding->vertexBuffer;
+        MBGL_CHECK_ERROR(glEnableVertexAttribArray(location));
+        MBGL_CHECK_ERROR(glVertexAttribPointer(
+            location,
+            static_cast<GLint>(binding->attributeSize),
+            static_cast<GLenum>(binding->attributeType),
+            static_cast<GLboolean>(false),
+            static_cast<GLsizei>(binding->vertexSize),
+            reinterpret_cast<GLvoid*>(binding->attributeOffset + (binding->vertexSize * binding->vertexOffset))));
+    } else {
+        MBGL_CHECK_ERROR(glDisableVertexAttribArray(location));
+    }
+}
+
 const constexpr PixelStorePack::Type PixelStorePack::Default;
 
 void PixelStorePack::Set(const Type& value) {
diff --git a/src/mbgl/gl/value.hpp b/src/mbgl/gl/value.hpp
index d4c7b5cdc3..19e9af194f 100644
--- a/src/mbgl/gl/value.hpp
+++ b/src/mbgl/gl/value.hpp
@@ -4,6 +4,7 @@
 #include <mbgl/gl/depth_mode.hpp>
 #include <mbgl/gl/stencil_mode.hpp>
 #include <mbgl/gl/color_mode.hpp>
+#include <mbgl/gl/attribute.hpp>
 #include <mbgl/util/color.hpp>
 #include <mbgl/util/size.hpp>
 #include <mbgl/util/range.hpp>
@@ -239,6 +240,12 @@ struct BindVertexArray {
     static Type Get(const Context&);
 };
 
+struct VertexAttribute {
+    using Type = optional<gl::AttributeBinding>;
+    static const Type Default;
+    static void Set(const Type&, Context&, AttributeLocation);
+};
+
 struct PixelStorePack {
     using Type = PixelStorageType;
     static const constexpr Type Default = { 4 };
diff --git a/src/mbgl/gl/vertex_array.cpp b/src/mbgl/gl/vertex_array.cpp
new file mode 100644
index 0000000000..68a500ac45
--- /dev/null
+++ b/src/mbgl/gl/vertex_array.cpp
@@ -0,0 +1,18 @@
+#include <mbgl/gl/vertex_array.hpp>
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/gl.hpp>
+
+namespace mbgl {
+namespace gl {
+
+void VertexArray::bind(Context& context, BufferID indexBuffer, const AttributeBindingArray& bindings) {
+    context.bindVertexArray = state->vertexArray;
+    state->indexBuffer = indexBuffer;
+
+    for (AttributeLocation location = 0; location < MAX_ATTRIBUTES; ++location) {
+        state->bindings[location] = bindings[location];
+    }
+}
+
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/vertex_array.hpp b/src/mbgl/gl/vertex_array.hpp
new file mode 100644
index 0000000000..9ccf48d9bd
--- /dev/null
+++ b/src/mbgl/gl/vertex_array.hpp
@@ -0,0 +1,58 @@
+#pragma once
+
+#include <mbgl/gl/object.hpp>
+#include <mbgl/gl/attribute.hpp>
+#include <mbgl/gl/state.hpp>
+#include <mbgl/gl/value.hpp>
+
+#include <array>
+#include <memory>
+
+namespace mbgl {
+namespace gl {
+
+class Context;
+
+class VertexArrayState {
+public:
+    VertexArrayState(UniqueVertexArray vertexArray_, Context& context)
+        : vertexArray(std::move(vertexArray_)),
+          bindings(makeBindings(context, std::make_index_sequence<MAX_ATTRIBUTES>())) {
+    }
+
+    void setDirty() {
+        indexBuffer.setDirty();
+        for (auto& binding : bindings) {
+            binding.setDirty();
+        }
+    }
+
+    UniqueVertexArray vertexArray;
+    State<value::BindElementBuffer> indexBuffer;
+
+    using AttributeState = State<value::VertexAttribute, Context&, AttributeLocation>;
+    std::array<AttributeState, MAX_ATTRIBUTES> bindings;
+
+private:
+    template <std::size_t... I>
+    std::array<AttributeState, MAX_ATTRIBUTES> makeBindings(Context& context, std::index_sequence<I...>) {
+        return {{ AttributeState { context, I }... }};
+    }
+};
+
+using UniqueVertexArrayState = std::unique_ptr<VertexArrayState, std::function<void (VertexArrayState*)>>;
+
+class VertexArray {
+public:
+    VertexArray(UniqueVertexArrayState state_)
+        : state(std::move(state_)) {
+    }
+
+    void bind(Context&, BufferID indexBuffer, const AttributeBindingArray&);
+
+private:
+    UniqueVertexArrayState state;
+};
+
+} // namespace gl
+} // namespace mbgl