From cf83f117f0e3e338454ba1bc0e5a13b3b9565228 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Mon, 10 Jul 2017 12:19:23 -0700
Subject: [core] Reduce memory requirements of VertexArrays

---
 src/mbgl/gl/attribute.hpp    | 22 ++++++++++++++--------
 src/mbgl/gl/context.cpp      |  5 +++--
 src/mbgl/gl/types.hpp        |  2 +-
 src/mbgl/gl/vertex_array.hpp | 17 ++++++++++++++++-
 4 files changed, 34 insertions(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/mbgl/gl/attribute.hpp b/src/mbgl/gl/attribute.hpp
index ed4168c21f..a85b49c6a5 100644
--- a/src/mbgl/gl/attribute.hpp
+++ b/src/mbgl/gl/attribute.hpp
@@ -12,6 +12,7 @@
 #include <functional>
 #include <string>
 #include <array>
+#include <limits>
 
 namespace mbgl {
 namespace gl {
@@ -30,12 +31,12 @@ template <> struct DataTypeOf<float>    : std::integral_constant<DataType, DataT
 class AttributeBinding {
 public:
     DataType attributeType;
-    std::size_t attributeSize;
-    std::size_t attributeOffset;
+    uint8_t attributeSize;
+    uint32_t attributeOffset;
 
     BufferID vertexBuffer;
-    std::size_t vertexSize;
-    std::size_t vertexOffset;
+    uint32_t vertexSize;
+    uint32_t vertexOffset;
 
     friend bool operator==(const AttributeBinding& lhs,
                            const AttributeBinding& rhs) {
@@ -71,20 +72,25 @@ public:
                            std::size_t attributeIndex,
                            std::size_t attributeSize = N) {
         static_assert(std::is_standard_layout<Vertex>::value, "vertex type must use standard layout");
+        assert(attributeSize >= 1);
+        assert(attributeSize <= 4);
+        assert(Vertex::attributeOffsets[attributeIndex] <= std::numeric_limits<uint32_t>::max());
+        static_assert(sizeof(Vertex) <= std::numeric_limits<uint32_t>::max(), "vertex too large");
         return AttributeBinding {
             DataTypeOf<T>::value,
-            attributeSize,
-            Vertex::attributeOffsets[attributeIndex],
+            static_cast<uint8_t>(attributeSize),
+            static_cast<uint32_t>(Vertex::attributeOffsets[attributeIndex]),
             buffer.buffer,
-            sizeof(Vertex),
+            static_cast<uint32_t>(sizeof(Vertex)),
             0,
         };
     }
 
     static optional<Binding> offsetBinding(const optional<Binding>& binding, std::size_t vertexOffset) {
+        assert(vertexOffset <= std::numeric_limits<uint32_t>::max());
         if (binding) {
             AttributeBinding result = *binding;
-            result.vertexOffset = vertexOffset;
+            result.vertexOffset = static_cast<uint32_t>(vertexOffset);
             return result;
         } else {
             return binding;
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 2d7354a64e..19ea9a514f 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -233,11 +233,12 @@ 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) };
+        UniqueVertexArray vao(std::move(id), { this });
+        return { UniqueVertexArrayState(new VertexArrayState(std::move(vao), *this), VertexArrayStateDeleter { true })};
     } 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*) {}) };
+        return { UniqueVertexArrayState(&globalVertexArrayState, VertexArrayStateDeleter { false }) };
     }
 }
 
diff --git a/src/mbgl/gl/types.hpp b/src/mbgl/gl/types.hpp
index c80399016e..e7d2ca449a 100644
--- a/src/mbgl/gl/types.hpp
+++ b/src/mbgl/gl/types.hpp
@@ -24,7 +24,7 @@ enum class ShaderType : uint32_t {
     Fragment = 0x8B30
 };
 
-enum class DataType : uint32_t {
+enum class DataType : uint16_t {
     Byte = 0x1400,
     UnsignedByte = 0x1401,
     Short = 0x1402,
diff --git a/src/mbgl/gl/vertex_array.hpp b/src/mbgl/gl/vertex_array.hpp
index 9ccf48d9bd..46c67017bb 100644
--- a/src/mbgl/gl/vertex_array.hpp
+++ b/src/mbgl/gl/vertex_array.hpp
@@ -40,7 +40,22 @@ private:
     }
 };
 
-using UniqueVertexArrayState = std::unique_ptr<VertexArrayState, std::function<void (VertexArrayState*)>>;
+class VertexArrayStateDeleter {
+public:
+    VertexArrayStateDeleter(bool destroy_)
+        : destroy(destroy_) {}
+
+    void operator()(VertexArrayState* ptr) const {
+        if (destroy) {
+            delete ptr;
+        }
+    }
+
+private:
+    bool destroy;
+};
+
+using UniqueVertexArrayState = std::unique_ptr<VertexArrayState, VertexArrayStateDeleter>;
 
 class VertexArray {
 public:
-- 
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