internal GLGraphicsContext(Func <string, IntPtr> getProcAddress, int maxVertices)
: base(maxVertices)
{
glInit(getProcAddress, 4, 0);
glClearColor(_clearColor.R, _clearColor.G, _clearColor.B, _clearColor.A);
_vertexBuffer = glGenBuffer();
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, Vertex.SizeInBytes * maxVertices, IntPtr.Zero, GL_DYNAMIC_DRAW);
GLUtility.CheckErrors(nameof(glBufferData));
_vertexArray = glGenVertexArray();
glBindVertexArray(_vertexArray);
glVertexAttribPointer(0, 3, GL_FLOAT, false, Vertex.SizeInBytes, IntPtr.Zero);
GLUtility.CheckErrors(nameof(glVertexAttribPointer));
glVertexAttribPointer(1, 4, GL_FLOAT, false, Vertex.SizeInBytes, (IntPtr)Marshal.SizeOf <Vector3>());
GLUtility.CheckErrors(nameof(glVertexAttribPointer));
glVertexAttribPointer(2, 2, GL_FLOAT, false, Vertex.SizeInBytes, (IntPtr)(Marshal.SizeOf <Vector3>() + Marshal.SizeOf <Vector4>()));
GLUtility.CheckErrors(nameof(glVertexAttribPointer));
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
ushort[] indices = new ushort[1024 * 6];
for (ushort i = 0, vertex = 0; i < indices.Length; i += 6, vertex += 4)
{
indices[i] = vertex;
indices[i + 1] = (ushort)(vertex + 1);
indices[i + 2] = (ushort)(vertex + 3);
indices[i + 3] = (ushort)(vertex + 1);
indices[i + 4] = (ushort)(vertex + 2);
indices[i + 5] = (ushort)(vertex + 3);
}
_indexBuffer = glGenBuffer();
glBindBuffer(GL_ARRAY_BUFFER, _indexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(ushort) * indices.Length, indices, GL_STATIC_DRAW);
GLUtility.CheckErrors(nameof(glBufferData));
uint vertexShader = GLUtility.CreateAndCompileShader(GL_VERTEX_SHADER, VertexShaderCode);
uint fragmentShader = GLUtility.CreateAndCompileShader(GL_FRAGMENT_SHADER, FragmentShaderCode);
_program = GLUtility.CreateAndLinkProgram(vertexShader, fragmentShader);
_vertTranformLocation = glGetUniformLocation(_program, "vertTransform");
_fragSamplerLocation = glGetUniformLocation(_program, "fragSampler");
glDisable(GL_CULL_FACE);
glCullFace(GL_BACK);
glFrontFace(GL_CW);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glActiveTexture(GL_TEXTURE0);
}