1 files changed, 101 insertions, 0 deletions
diff --git a/include/mbgl/geometry/vao.hpp b/include/mbgl/geometry/vao.hpp
new file mode 100644
index 0000000000..71d7ff89fe
--- /dev/null
+++ b/include/mbgl/geometry/vao.hpp
@@ -0,0 +1,101 @@
+#ifndef MBGL_GEOMETRY_VAO
+#define MBGL_GEOMETRY_VAO
+
+#include <mbgl/platform/gl.hpp>
+
+#include <stdexcept>
+
+namespace mbgl {
+
+class VertexArrayObject {
+public:
+    template <typename Shader, typename VertexBuffer>
+    void bind(Shader& shader, VertexBuffer& vertex_buffer, char *offset) {
+#ifdef GL_ARB_vertex_array_object
+        if (!vao) {
+            glGenVertexArrays(1, &vao);
+            glBindVertexArray(vao);
+        } else {
+            // We have been given the correct information.
+            glBindVertexArray(vao);
+        }
+
+        if (shader_ptr != &shader) {
+            if (shader_ptr != nullptr) {
+                fprintf(stderr, "shader rebind!");
+            }
+#endif
+            vertex_buffer.bind();
+            shader.bind(offset);
+
+#ifdef GL_ARB_vertex_array_object
+            shader_ptr = &shader;
+            vertex_buffer_ptr = &vertex_buffer;
+            elements_buffer_ptr = nullptr;
+            offset_ptr = offset;
+        } else if (vertex_buffer_ptr != &vertex_buffer) {
+            throw std::runtime_error("trying to bind VAO to another vertex buffer");
+        } else if (elements_buffer_ptr != nullptr) {
+            throw std::runtime_error("trying to bind VAO to another elements buffer");
+        } else if (offset_ptr != offset) {
+            throw std::runtime_error("trying to bind VAO to another offset");
+        }
+#endif
+    }
+
+    template <typename Shader, typename VertexBuffer, typename ElementsBuffer>
+    void bind(Shader& shader, VertexBuffer& vertex_buffer, ElementsBuffer& elements_buffer, char *offset) {
+#ifdef GL_ARB_vertex_array_object
+        if (!vao) {
+            glGenVertexArrays(1, &vao);
+            glBindVertexArray(vao);
+        } else {
+            // We have been given the correct information.
+            glBindVertexArray(vao);
+        }
+
+        if (shader_ptr != &shader) {
+#endif
+            vertex_buffer.bind();
+            elements_buffer.bind();
+            shader.bind(offset);
+
+#ifdef GL_ARB_vertex_array_object
+            shader_ptr = &shader;
+            vertex_buffer_ptr = &vertex_buffer;
+            elements_buffer_ptr = &elements_buffer;
+            offset_ptr = offset;
+        } else if (vertex_buffer_ptr != &vertex_buffer) {
+            throw std::runtime_error("trying to bind VAO to another vertex buffer");
+        } else if (elements_buffer_ptr != &elements_buffer) {
+            throw std::runtime_error("trying to bind VAO to another elements buffer");
+        } else if (offset_ptr != offset) {
+            throw std::runtime_error("trying to bind VAO to another offset");
+        }
+#endif
+    }
+
+    ~VertexArrayObject() {
+#ifdef GL_ARB_vertex_array_object
+        if (vao) {
+            glDeleteVertexArrays(1, &vao);
+        }
+#endif
+    }
+
+private:
+#ifdef GL_ARB_vertex_array_object
+    GLuint vao = 0;
+
+    // For debug reasons, we're storing the bind information so that we can
+    // detect errors and report
+    void *shader_ptr = nullptr;
+    void *vertex_buffer_ptr = nullptr;
+    void *elements_buffer_ptr = nullptr;
+    char *offset_ptr = 0;
+#endif
+};
+
+}
+
+#endif