glium 0.32.1

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
Documentation 
use std::borrow::Borrow;
use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::mem;

use smallvec::SmallVec;

use crate::Handle;
use crate::buffer::BufferAnySlice;
use crate::program::Program;
use crate::vertex::AttributeType;
use crate::vertex::VertexFormat;
use crate::GlObject;
use crate::BufferExt;

use crate::gl;
use crate::context::CommandContext;
use crate::version::Api;
use crate::version::Version;

/// Stores and handles vertex attributes.
pub struct VertexAttributesSystem {
    // we maintain a list of VAOs for each vertexbuffer-indexbuffer-program association
    // the key is a (buffers-list-with-offset, program) ; the buffers list must be sorted
    vaos: RefCell<HashMap<(Vec<(gl::types::GLuint, usize)>, Handle), VertexArrayObject>>,
}

/// Object allowing one to bind vertex attributes to the current context.
pub struct Binder<'a, 'b, 'c> {
    context: &'b mut CommandContext<'c>,
    program: &'a Program,
    element_array_buffer: Option<BufferAnySlice<'a>>,
    vertex_buffers: SmallVec<[(gl::types::GLuint, VertexFormat, usize, usize, Option<u32>); 2]>,
    base_vertex: bool,
}

impl VertexAttributesSystem {
    /// Builds a new `VertexAttributesSystem`.
    #[inline]
    pub fn new() -> VertexAttributesSystem {
        VertexAttributesSystem {
            vaos: RefCell::new(HashMap::with_hasher(Default::default())),
        }
    }

    /// Starts the process of binding vertex attributes.
    ///
    /// `base_vertex` should be set to true if the backend supports the `glDraw*BaseVertex`
    /// functions. If `base_vertex` is true, then `bind` will return the base vertex to use.
    #[inline]
    pub fn start<'a, 'b, 'c: 'b>(ctxt: &'b mut CommandContext<'c>, program: &'a Program,
                                 indices: Option<BufferAnySlice<'a>>, base_vertex: bool)
                                 -> Binder<'a, 'b, 'c>
    {
        if let Some(indices) = indices {
            indices.prepare_for_element_array(ctxt);
        }

        Binder {
            context: ctxt,
            program,
            element_array_buffer: indices,
            vertex_buffers: SmallVec::new(),
            base_vertex,
        }
    }

    /// This function *must* be called whenever you destroy a buffer so that the system can
    /// purge its VAOs cache.
    #[inline]
    pub fn purge_buffer(ctxt: &mut CommandContext<'_>, id: gl::types::GLuint) {
        VertexAttributesSystem::purge_if(ctxt, |&(ref buffers, _)| {
            buffers.iter().any(|&(b, _)| b == id)
        })
    }

    /// This function *must* be called whenever you destroy a program so that the system can
    /// purge its VAOs cache.
    #[inline]
    pub fn purge_program(ctxt: &mut CommandContext<'_>, program: Handle) {
        VertexAttributesSystem::purge_if(ctxt, |&(_, p)| p == program)
    }

    /// Purges the VAOs cache.
    pub fn purge_all(ctxt: &mut CommandContext<'_>) {
        let vaos = mem::replace(&mut *ctxt.vertex_array_objects.vaos.borrow_mut(),
                                HashMap::with_hasher(Default::default()));

        for (_, vao) in vaos {
            vao.destroy(ctxt);
        }
    }

    /// Purges the VAOs cache. Contrary to `purge_all`, this function expects the system to be
    /// destroyed soon.
    pub fn cleanup(ctxt: &mut CommandContext<'_>) {
        let vaos = mem::replace(&mut *ctxt.vertex_array_objects.vaos.borrow_mut(),
                                HashMap::with_hasher(Default::default()));

        for (_, vao) in vaos {
            vao.destroy(ctxt);
        }
    }

    /// Tells the VAOs system that the currently bound element array buffer will change.
    pub fn hijack_current_element_array_buffer(ctxt: &mut CommandContext<'_>) {
        let vaos = ctxt.vertex_array_objects.vaos.borrow_mut();

        for (_, vao) in vaos.iter() {
            if vao.id == ctxt.state.vertex_array {
                vao.element_array_buffer_hijacked.set(true);
                return;
            }
        }
    }

    /// Purges VAOs that match a certain condition.
    fn purge_if<F>(ctxt: &mut CommandContext<'_>, mut condition: F)
                   where F: FnMut(&(Vec<(gl::types::GLuint, usize)>, Handle)) -> bool
    {
        let mut vaos = ctxt.vertex_array_objects.vaos.borrow_mut();

        let mut keys = Vec::with_capacity(4);
        for key in (*vaos).keys() {
            if condition(key) {
                keys.push(key.clone());
            }
        }

        for key in keys {
            vaos.remove(&key).unwrap().destroy(ctxt);
        }
    }
}

impl<'a, 'b, 'c> Binder<'a, 'b, 'c> {
    /// Adds a buffer to bind as a source of vertices.
    ///
    /// # Parameters
    ///
    /// - `buffer`: The buffer to bind.
    /// - `first`: Offset of the first element of the buffer in number of elements.
    /// - `divisor`: If `Some`, use this value for `glVertexAttribDivisor` (instancing-related).
    #[inline]
    pub fn add(mut self, buffer: &BufferAnySlice<'_>, bindings: &VertexFormat, divisor: Option<u32>)
               -> Binder<'a, 'b, 'c>
    {
        let offset = buffer.get_offset_bytes();

        buffer.prepare_for_vertex_attrib_array(self.context);

        let (buffer, format, stride) = (buffer.get_id(), bindings.clone(),
                                        buffer.get_elements_size());

        self.vertex_buffers.push((buffer, format, offset, stride, divisor));
        self
    }

    /// Finish binding the vertex attributes.
    ///
    /// If `base_vertex` was set to true, returns the base vertex to use when drawing.
    pub fn bind(mut self) -> Option<gl::types::GLint> {
        let ctxt = self.context;

        if ctxt.version >= &Version(Api::Gl, 3, 0) || ctxt.version >= &Version(Api::GlEs, 3, 0) ||
           ctxt.extensions.gl_arb_vertex_array_object || ctxt.extensions.gl_oes_vertex_array_object
           || ctxt.extensions.gl_apple_vertex_array_object
        {
            // VAOs are supported

            // finding the base vertex
            let base_vertex = if self.base_vertex {
                Some(self.vertex_buffers.iter()
                                        .filter(|&&(_, _, _, _, div)| div.is_none())
                                        .map(|&(_, _, off, stride, _)| off / stride)
                                        .min().unwrap_or(0))
            } else {
                None
            };

            // removing the offset corresponding to the base vertex
            if let Some(base_vertex) = base_vertex {
                for &mut (_, _, ref mut off, stride, _) in self.vertex_buffers.iter_mut() {
                    *off -= base_vertex * stride;
                }
            }

            let mut buffers_list: Vec<_> = self.vertex_buffers.iter()
                                                              .map(|&(v, _, o, s, _)| (v, o))
                                                              .collect();
            buffers_list.push((self.element_array_buffer.map(|b| b.get_id()).unwrap_or(0), 0));
            buffers_list.sort_unstable();

            let program_id = self.program.get_id();

            // trying to find an existing VAO in the cache
            if let Some(value) = ctxt.vertex_array_objects.vaos.borrow_mut()
                                     .get(&(buffers_list.clone(), program_id))
            {
                value.bind(ctxt);
                return base_vertex.map(|v| v as gl::types::GLint);
            }

            // if not found, building a new one
            let new_vao = unsafe {
                VertexArrayObject::new(ctxt, &self.vertex_buffers,
                                       self.element_array_buffer, self.program)
            };

            new_vao.bind(ctxt);
            ctxt.vertex_array_objects.vaos.borrow_mut().insert((buffers_list, program_id), new_vao);

            base_vertex.map(|v| v as gl::types::GLint)

        } else {
            // VAOs are not supported

            // just in case
            bind_vao(ctxt, 0);

            if let Some(element_array_buffer) = self.element_array_buffer {
                element_array_buffer.bind_to_element_array(ctxt);
            }

            for (vertex_buffer, bindings, offset, stride, divisor) in self.vertex_buffers.into_iter() {
                unsafe {
                    bind_attribute(ctxt, self.program, vertex_buffer, &bindings, offset, stride,
                                   divisor);
                }
            }

            // TODO: it is unlikely that a backend supports base vertex but not VAOs, so we just
            //       ignore this case ; however it would ideally be better to handle it
            if self.base_vertex {
                Some(0)
            } else {
                None
            }
        }
    }
}

/// Stores informations about how to bind a vertex buffer, an index buffer and a program.
struct VertexArrayObject {
    id: gl::types::GLuint,
    destroyed: bool,
    element_array_buffer: gl::types::GLuint,
    element_array_buffer_hijacked: Cell<bool>,
}

impl VertexArrayObject {
    /// Builds a new `VertexArrayObject`.
    ///
    /// The vertex buffer, index buffer and program must not outlive the
    /// VAO, and the VB & program attributes must not change.
    unsafe fn new(mut ctxt: &mut CommandContext<'_>,
                  vertex_buffers: &[(gl::types::GLuint, VertexFormat, usize, usize, Option<u32>)],
                  index_buffer: Option<BufferAnySlice<'_>>, program: &Program) -> VertexArrayObject
    {
        // checking the attributes types
        for &(_, ref bindings, _, _, _) in vertex_buffers {
            for &(ref name, _, location, ty, _) in bindings.iter() {
                let attribute = match location {
                    -1 => {
                        // No location specified in Vertex Format. Check name instead
                        match program.get_attribute(Borrow::<str>::borrow(name)) {
                            Some(a) => a,
                            None => continue,
                        }
                    }
                    _ => {
                        match program.attributes().into_iter()
                                .find(|(_, a)| a.location == location) {
                            Some((_, a)) => a,
                            None => continue,
                        }
                    }
                };

                if ty.get_num_components() != attribute.ty.get_num_components() ||
                    attribute.size != 1
                {
                    panic!("The program attribute `{}` does not match the vertex format. \
                            Program expected {:?}, got {:?}.", name, attribute.ty, ty);
                }
            }
        }

        // checking for duplicate attribute locations
        for &(_, ref bindings, _, _, _) in vertex_buffers {
            for (i, bi) in bindings.iter().enumerate() {
                for (o, bo) in bindings.iter().enumerate() {
                    if i != o && bi.2 == bo.2 && bi.2 != -1 {
                        panic!("The program attribute `{}` has the same binding location as program attribute `{}` (binding location {})",
                               bi.0, bo.0, bi.2)
                    }
                }
            }
        }

        // checking for missing attributes
        for (&ref name, attribute) in program.attributes() {
            let mut found = false;
            for &(_, ref bindings, _, _, _) in vertex_buffers {
                if bindings.iter().any(|&(ref n, _, location, _, _)| (location != -1 && location == attribute.location) || n == name) {
                    found = true;
                    break;
                }
            }
            if !found {
                panic!("The program attribute `{}` is missing in the vertex bindings", name);
            }
        };

        // TODO: check for collisions between the vertices sources

        // building the VAO
        let id = {
            let mut id = 0;
            if ctxt.version >= &Version(Api::Gl, 3, 0) ||
                ctxt.version >= &Version(Api::GlEs, 3, 0) ||
                ctxt.extensions.gl_arb_vertex_array_object
            {
                ctxt.gl.GenVertexArrays(1, &mut id);
            } else if ctxt.extensions.gl_oes_vertex_array_object {
                ctxt.gl.GenVertexArraysOES(1, &mut id);
            } else if ctxt.extensions.gl_apple_vertex_array_object {
                ctxt.gl.GenVertexArraysAPPLE(1, &mut id);
            } else {
                unreachable!();
            };
            id
        };

        // we don't use DSA as we're going to make multiple calls for this VAO
        // and we're likely going to use the VAO right after it's been created
        bind_vao(&mut ctxt, id);

        // binding index buffer
        if let Some(index_buffer) = index_buffer {
            index_buffer.bind_to_element_array(&mut ctxt);
        }

        for &(vertex_buffer, ref bindings, offset, stride, divisor) in vertex_buffers {
            bind_attribute(ctxt, program, vertex_buffer, bindings, offset, stride, divisor);
        }

        VertexArrayObject {
            id,
            destroyed: false,
            element_array_buffer: index_buffer.map(|b| b.get_id()).unwrap_or(0),
            element_array_buffer_hijacked: Cell::new(false),
        }
    }

    /// Sets this VAO as the current VAO.
    fn bind(&self, ctxt: &mut CommandContext<'_>) {
        unsafe {
            bind_vao(ctxt, self.id);

            if self.element_array_buffer_hijacked.get() {
                // TODO: use a proper function
                if ctxt.version >= &Version(Api::Gl, 1, 5) ||
                    ctxt.version >= &Version(Api::GlEs, 2, 0)
                {
                    ctxt.gl.BindBuffer(gl::ELEMENT_ARRAY_BUFFER, self.element_array_buffer);
                } else if ctxt.extensions.gl_arb_vertex_buffer_object {
                    ctxt.gl.BindBufferARB(gl::ELEMENT_ARRAY_BUFFER_ARB, self.element_array_buffer);
                } else {
                    unreachable!();
                }

                self.element_array_buffer_hijacked.set(false);
            }
        }
    }

    /// Must be called to destroy the VAO (otherwise its destructor will panic as a safety
    /// measure).
    fn destroy(mut self, ctxt: &mut CommandContext<'_>) {
        self.destroyed = true;

        // unbinding
        if ctxt.state.vertex_array == self.id {
            ctxt.state.vertex_array = 0;
        }

        // deleting
        if ctxt.version >= &Version(Api::Gl, 3, 0) ||
            ctxt.version >= &Version(Api::GlEs, 3, 0) ||
            ctxt.extensions.gl_arb_vertex_array_object
        {
            unsafe { ctxt.gl.DeleteVertexArrays(1, [ self.id ].as_ptr()) };
        } else if ctxt.extensions.gl_oes_vertex_array_object {
            unsafe { ctxt.gl.DeleteVertexArraysOES(1, [ self.id ].as_ptr()) };
        } else if ctxt.extensions.gl_apple_vertex_array_object {
            unsafe { ctxt.gl.DeleteVertexArraysAPPLE(1, [ self.id ].as_ptr()) };
        } else {
            unreachable!();
        }
    }
}

impl Drop for VertexArrayObject {
    #[inline]
    fn drop(&mut self) {
        assert!(self.destroyed);
    }
}

impl GlObject for VertexArrayObject {
    type Id = gl::types::GLuint;

    #[inline]
    fn get_id(&self) -> gl::types::GLuint {
        self.id
    }
}

fn vertex_binding_type_to_gl(ty: AttributeType) -> (gl::types::GLenum, gl::types::GLint, gl::types::GLint) {
    match ty {
        AttributeType::I8 => (gl::BYTE, 1, 1),
        AttributeType::I8I8 => (gl::BYTE, 2, 1),
        AttributeType::I8I8I8 => (gl::BYTE, 3, 1),
        AttributeType::I8I8I8I8 => (gl::BYTE, 4, 1),
        AttributeType::U8 => (gl::UNSIGNED_BYTE, 1, 1),
        AttributeType::U8U8 => (gl::UNSIGNED_BYTE, 2, 1),
        AttributeType::U8U8U8 => (gl::UNSIGNED_BYTE, 3, 1),
        AttributeType::U8U8U8U8 => (gl::UNSIGNED_BYTE, 4, 1),
        AttributeType::I16 => (gl::SHORT, 1, 1),
        AttributeType::I16I16 => (gl::SHORT, 2, 1),
        AttributeType::I16I16I16 => (gl::SHORT, 3, 1),
        AttributeType::I16I16I16I16 => (gl::SHORT, 4, 1),
        AttributeType::U16 => (gl::UNSIGNED_SHORT, 1, 1),
        AttributeType::U16U16 => (gl::UNSIGNED_SHORT, 2, 1),
        AttributeType::U16U16U16 => (gl::UNSIGNED_SHORT, 3, 1),
        AttributeType::U16U16U16U16 => (gl::UNSIGNED_SHORT, 4, 1),
        AttributeType::I32 => (gl::INT, 1, 1),
        AttributeType::I32I32 => (gl::INT, 2, 1),
        AttributeType::I32I32I32 => (gl::INT, 3, 1),
        AttributeType::I32I32I32I32 => (gl::INT, 4, 1),
        AttributeType::U32 => (gl::UNSIGNED_INT, 1, 1),
        AttributeType::U32U32 => (gl::UNSIGNED_INT, 2, 1),
        AttributeType::U32U32U32 => (gl::UNSIGNED_INT, 3, 1),
        AttributeType::U32U32U32U32 => (gl::UNSIGNED_INT, 4, 1),
        AttributeType::I64 => (gl::INT64_NV, 1, 1),
        AttributeType::I64I64 => (gl::INT64_NV, 2, 1),
        AttributeType::I64I64I64 => (gl::INT64_NV, 3, 1),
        AttributeType::I64I64I64I64 => (gl::INT64_NV, 4, 1),
        AttributeType::U64 => (gl::UNSIGNED_INT64_NV, 1, 1),
        AttributeType::U64U64 => (gl::UNSIGNED_INT64_NV, 2, 1),
        AttributeType::U64U64U64 => (gl::UNSIGNED_INT64_NV, 3, 1),
        AttributeType::U64U64U64U64 => (gl::UNSIGNED_INT64_NV, 4, 1),
        AttributeType::F16 => (gl::HALF_FLOAT, 1, 1),
        AttributeType::F16F16 => (gl::HALF_FLOAT, 2, 1),
        AttributeType::F16F16F16 => (gl::HALF_FLOAT, 3, 1),
        AttributeType::F16F16F16F16 => (gl::HALF_FLOAT, 4, 1),
        AttributeType::F16x2x2 => (gl::HALF_FLOAT, 2, 2),
        AttributeType::F16x2x3 => (gl::HALF_FLOAT, 2, 3),
        AttributeType::F16x2x4 => (gl::HALF_FLOAT, 2, 4),
        AttributeType::F16x3x2 => (gl::HALF_FLOAT, 3, 2),
        AttributeType::F16x3x3 => (gl::HALF_FLOAT, 3, 3),
        AttributeType::F16x3x4 => (gl::HALF_FLOAT, 3, 4),
        AttributeType::F16x4x2 => (gl::HALF_FLOAT, 4, 2),
        AttributeType::F16x4x3 => (gl::HALF_FLOAT, 4, 3),
        AttributeType::F16x4x4 => (gl::HALF_FLOAT, 4, 4),
        AttributeType::F32 => (gl::FLOAT, 1, 1),
        AttributeType::F32F32 => (gl::FLOAT, 2, 1),
        AttributeType::F32F32F32 => (gl::FLOAT, 3, 1),
        AttributeType::F32F32F32F32 => (gl::FLOAT, 4, 1),
        AttributeType::F32x2x2 => (gl::FLOAT, 2, 2),
        AttributeType::F32x2x3 => (gl::FLOAT, 2, 3),
        AttributeType::F32x2x4 => (gl::FLOAT, 2, 4),
        AttributeType::F32x3x2 => (gl::FLOAT, 3, 2),
        AttributeType::F32x3x3 => (gl::FLOAT, 3, 3),
        AttributeType::F32x3x4 => (gl::FLOAT, 3, 4),
        AttributeType::F32x4x2 => (gl::FLOAT, 4, 2),
        AttributeType::F32x4x3 => (gl::FLOAT, 4, 3),
        AttributeType::F32x4x4 => (gl::FLOAT, 4, 4),
        AttributeType::F64 => (gl::DOUBLE, 1, 1),
        AttributeType::F64F64 => (gl::DOUBLE, 2, 1),
        AttributeType::F64F64F64 => (gl::DOUBLE, 3, 1),
        AttributeType::F64F64F64F64 => (gl::DOUBLE, 4, 1),
        AttributeType::F64x2x2 => (gl::DOUBLE, 2, 2),
        AttributeType::F64x2x3 => (gl::DOUBLE, 2, 3),
        AttributeType::F64x2x4 => (gl::DOUBLE, 2, 4),
        AttributeType::F64x3x2 => (gl::DOUBLE, 3, 2),
        AttributeType::F64x3x3 => (gl::DOUBLE, 3, 3),
        AttributeType::F64x3x4 => (gl::DOUBLE, 3, 4),
        AttributeType::F64x4x2 => (gl::DOUBLE, 4, 2),
        AttributeType::F64x4x3 => (gl::DOUBLE, 4, 3),
        AttributeType::F64x4x4 => (gl::DOUBLE, 4, 4),
        AttributeType::I2I10I10I10Reversed => (gl::INT_2_10_10_10_REV, 4, 1),
        AttributeType::U2U10U10U10Reversed => (gl::UNSIGNED_INT_2_10_10_10_REV, 4, 1),
        AttributeType::I10I10I10I2 => (gl::INT_10_10_10_2_OES, 4, 1),
        AttributeType::U10U10U10U2 => (gl::UNSIGNED_INT_10_10_10_2_OES, 4, 1),
        AttributeType::F10F11F11UnsignedIntReversed => (gl::UNSIGNED_INT_10F_11F_11F_REV, 3, 1),
        AttributeType::FixedFloatI16U16 => (gl::FIXED, 1, 1),
    }
}

/// Binds the vertex array object as the current one. Unbinds if `0` is passed.
///
/// ## Panic
///
/// Panics if the backend doesn't support vertex array objects.
fn bind_vao(ctxt: &mut CommandContext<'_>, vao_id: gl::types::GLuint) {
    if ctxt.state.vertex_array != vao_id {
        if ctxt.version >= &Version(Api::Gl, 3, 0) ||
            ctxt.version >= &Version(Api::GlEs, 3, 0) ||
            ctxt.extensions.gl_arb_vertex_array_object
        {
            unsafe { ctxt.gl.BindVertexArray(vao_id) };
        } else if ctxt.extensions.gl_oes_vertex_array_object {
            unsafe { ctxt.gl.BindVertexArrayOES(vao_id) };
        } else if ctxt.extensions.gl_apple_vertex_array_object {
            unsafe { ctxt.gl.BindVertexArrayAPPLE(vao_id) };
        } else {
            unreachable!();
        }

        ctxt.state.vertex_array = vao_id;
    }
}

/// Binds an individual attribute to the current VAO.
unsafe fn bind_attribute(ctxt: &mut CommandContext<'_>, program: &Program,
                         vertex_buffer: gl::types::GLuint, bindings: &VertexFormat,
                         buffer_offset: usize, stride: usize, divisor: Option<u32>)
{
    // glVertexAttribPointer uses the current array buffer
    // TODO: use a proper function
    if ctxt.state.array_buffer_binding != vertex_buffer {
        if ctxt.version >= &Version(Api::Gl, 1, 5) ||
            ctxt.version >= &Version(Api::GlEs, 2, 0)
        {
            ctxt.gl.BindBuffer(gl::ARRAY_BUFFER, vertex_buffer);
        } else if ctxt.extensions.gl_arb_vertex_buffer_object {
            ctxt.gl.BindBufferARB(gl::ARRAY_BUFFER_ARB, vertex_buffer);
        } else {
            unreachable!();
        }
        ctxt.state.array_buffer_binding = vertex_buffer;
    }

    // binding attributes
    for &(ref name, offset, location, ty, normalize) in bindings.iter() {
        let (data_type, elements_count, instances_count) = vertex_binding_type_to_gl(ty);

        let attribute = match location {
            -1 => {
                // No location specified in Vertex Format. Check name instead
                match program.get_attribute(Borrow::<str>::borrow(name)) {
                    Some(a) => a,
                    None => continue,
                }
            }
            _ => {
                match program.attributes().into_iter()
                        .find(|(_, a)| a.location == location) {
                    Some((_, a)) => a,
                    None => continue,
                }
            }
        };

        if attribute.location != -1 {
            let (attribute_ty, _, _) = vertex_binding_type_to_gl(attribute.ty);
            if normalize {
                for i in 0..instances_count {
                    ctxt.gl.VertexAttribPointer((attribute.location + i) as u32,
                                                elements_count as gl::types::GLint, data_type, 1,
                                                stride as i32,
                                                (buffer_offset + offset + (i * elements_count * 4) as usize) as *const _)
                }
            } else {
                match attribute_ty {
                    gl::BYTE | gl::UNSIGNED_BYTE | gl::SHORT | gl::UNSIGNED_SHORT |
                    gl::INT | gl::UNSIGNED_INT =>
                        ctxt.gl.VertexAttribIPointer(attribute.location as u32,
                                                     elements_count as gl::types::GLint, data_type,
                                                     stride as i32,
                                                     (buffer_offset + offset) as *const _),

                    gl::FLOAT => {
                        for i in 0..instances_count {
                            ctxt.gl.VertexAttribPointer((attribute.location + i) as u32,
                                                        elements_count as gl::types::GLint, data_type, 0,
                                                        stride as i32,
                                                        (buffer_offset + offset + (i * elements_count * 4) as usize) as *const _)
                        }
                    },

                    gl::DOUBLE | gl::INT64_NV | gl::UNSIGNED_INT64_NV => {
                        for i in 0..instances_count {
                            ctxt.gl.VertexAttribLPointer((attribute.location + i) as u32,
                                                         elements_count as gl::types::GLint, data_type,
                                                         stride as i32,
                                                         (buffer_offset + offset + (i * elements_count * 8) as usize) as *const _)
                        }
                    },

                    _ => unreachable!()
                }
            }

            for i in 0..instances_count {
                if let Some(divisor) = divisor {
                    ctxt.gl.VertexAttribDivisor((attribute.location + i) as u32, divisor);
                }
                ctxt.gl.EnableVertexAttribArray((attribute.location + i) as u32);
            }
        }
    }
}