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//! This crate provides a binding for the Khronos EGL 1.5 API.
//! It was originally a fork of the [egl](https://crates.io/crates/egl) crate,
//! which is left unmaintained.
//!
//! ## Usage
//!
//! You can access the EGL API using an [`Instance`]
//! object defined by either statically linking with `libEGL.so.1` at compile time,
//! or dynamically loading the EGL library at runtime.
//!
//! ### Static linking
//!
//! You must enable static linking using the `static` feature in your `Cargo.toml`:
//! ```toml
//! khronos-egl = { version = ..., features = ["static"] }
//! ```
//!
//! This will add a dependency to the [`pkg-config`](https://crates.io/crates/pkg-config) crate,
//! necessary to find the EGL library at compile time.
//! Here is a simple example showing how to use this library to create an EGL context when static linking is enabled.
//!
//! ```rust
//! extern crate khronos_egl as egl;
//!
//! fn main() -> Result<(), egl::Error> {
//! 	// Create an EGL API instance.
//! 	// The `egl::Static` API implementation is only available when the `static` feature is enabled.
//! 	let egl = egl::Instance::new(egl::Static);
//!
//! 	let wayland_display = wayland_client::Display::connect_to_env().expect("unable to connect to the wayland server");
//! 	let display = egl.get_display(wayland_display.get_display_ptr() as *mut std::ffi::c_void).unwrap();
//! 	egl.initialize(display)?;
//!
//! 	let attributes = [
//! 		egl::RED_SIZE, 8,
//! 		egl::GREEN_SIZE, 8,
//! 		egl::BLUE_SIZE, 8,
//! 		egl::NONE
//! 	];
//!
//! 	let config = egl.choose_first_config(display, &attributes)?.expect("unable to find an appropriate ELG configuration");
//!
//! 	let context_attributes = [
//! 		egl::CONTEXT_MAJOR_VERSION, 4,
//! 		egl::CONTEXT_MINOR_VERSION, 0,
//! 		egl::CONTEXT_OPENGL_PROFILE_MASK, egl::CONTEXT_OPENGL_CORE_PROFILE_BIT,
//! 		egl::NONE
//! 	];
//!
//! 	egl.create_context(display, config, None, &context_attributes);
//!
//! 	Ok(())
//! }
//! ```
//!
//! The creation of a `Display` instance is not detailed here since it depends on your display server.
//! It is created using the `get_display` function with a pointer to the display server connection handle.
//! For instance, if you are using the [wayland-client](https://crates.io/crates/wayland-client) crate,
//! you can get this pointer using the `Display::get_display_ptr` method.
//!
//! #### Static API Instance
//!
//! It may be bothering in some applications to pass the `Instance` to every fonction that needs to call the EGL API.
//! One workaround would be to define a static `Instance`,
//! which should be possible to define at compile time using static linking.
//! However this is not yet supported by the stable `rustc` compiler.
//! With the nightly compiler,
//! you can combine the `nightly` and `static` features so that this crate
//! can provide a static `Instance`, called `API` that can then be accessed everywhere.
//!
//! ```
//! # extern crate khronos_egl as egl;
//! use egl::API as egl;
//! ```
//!
//! ### Dynamic Linking
//!
//! Dynamic linking allows your application to accept multiple versions of EGL and be more flexible.
//! You must enable dynamic linking using the `dynamic` feature in your `Cargo.toml`:
//! ```toml
//! khronos-egl = { version = ..., features = ["dynamic"] }
//! ```
//!
//! This will add a dependency to the [`libloading`](https://crates.io/crates/libloading) crate,
//! necessary to find the EGL library at runtime.
//! You can then load the EGL API into a `Instance<Dynamic<libloading::Library>>` as follows:
//!
//! ```
//! # extern crate khronos_egl as egl;
//! let lib = libloading::Library::new("libEGL.so.1").expect("unable to find libEGL.so.1");
//! let egl = unsafe { egl::DynamicInstance::<egl::EGL1_4>::load_required_from(lib).expect("unable to load libEGL.so.1") };
//! ```
//!
//! Here, `egl::EGL1_4` is used to specify what is the minimum required version of EGL that must be provided by `libEGL.so.1`.
//! This will return a `DynamicInstance<egl::EGL1_4>`, however in that case where `libEGL.so.1` provides a more recent version of EGL,
//! you can still upcast ths instance to provide version specific features:
//! ```
//! # extern crate khronos_egl as egl;
//! # let lib = libloading::Library::new("libEGL.so.1").expect("unable to find libEGL.so.1");
//! # let egl = unsafe { egl::DynamicInstance::<egl::EGL1_4>::load_required_from(lib).expect("unable to load libEGL.so.1") };
//! match egl.upcast::<egl::EGL1_5>() {
//! 	Some(egl1_5) => {
//! 		// do something with EGL 1.5
//! 	}
//! 	None => {
//! 		// do something with EGL 1.4 instead.
//! 	}
//! };
//! ```
//!
//! ## Troubleshooting
//!
//! ### Static Linking with OpenGL ES
//!
//! When using OpenGL ES with `khronos-egl` with the `static` feature,
//! it is necessary to place a dummy extern at the top of your application which links libEGL first, then GLESv1/2.
//! This is because libEGL provides symbols required by GLESv1/2.
//! Here's how to work around this:
//!
//! ```
//! ##[link(name = "EGL")]
//! ##[link(name = "GLESv2")]
//! extern {}
//! ```
#![allow(non_upper_case_globals)]
#![allow(non_snake_case)]

extern crate libc;

use std::convert::{TryFrom, TryInto};
use std::ffi::CStr;
use std::ffi::CString;
use std::fmt;
use std::ptr;

use libc::{c_uint, c_char, c_void};

/// EGL API provider.
pub trait Api {
	/// Version of the provided EGL API.
	fn version(&self) -> Version;
}

pub trait Downcast<V> {
	fn downcast(&self) -> &V;
}

impl<T> Downcast<T> for T {
	fn downcast(&self) -> &T {
		self
	}
}

pub trait Upcast<V> {
	fn upcast(&self) -> Option<&V>;
}

impl<T> Upcast<T> for T {
	fn upcast(&self) -> Option<&T> {
		Some(self)
	}
}

/// EGL API instance.
///
/// An instance wraps an interface to the EGL API and provide
/// rust-friendly access to it.
pub struct Instance<T> {
	api: T
}

impl<T> Instance<T> {
	/// Cast the API.
	#[inline(always)]
	pub fn cast_into<U: From<T>>(self) -> Instance<U> {
		Instance {
			api: self.api.into()
		}
	}

	/// Try to cast the API.
	#[inline(always)]
	pub fn try_cast_into<U: TryFrom<T>>(self) -> Result<Instance<U>, Instance<U::Error>> {
		match self.api.try_into() {
			Ok(t) => Ok(Instance {
				api: t
			}),
			Err(e) => Err(Instance {
				api: e
			})
		}
	}

	/// Returns the version of the provided EGL API.
	#[inline(always)]
	pub fn version(&self) -> Version where T: Api {
		self.api.version()
	}
}

impl<T> Instance<T> {
	#[inline(always)]
	pub const fn new(api: T) -> Instance<T> {
		Instance {
			api
		}
	}
}

impl<T: fmt::Debug> fmt::Debug for Instance<T> {
	#[inline(always)]
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		write!(f, "Instance({:?})", self.api)
	}
}

impl<T> From<T> for Instance<T> {
	#[inline(always)]
	fn from(t: T) -> Instance<T> {
		Instance::new(t)
	}
}

// ------------------------------------------------------------------------------------------------
// Link
// ------------------------------------------------------------------------------------------------
#[cfg(feature = "static")]
#[link(name = "EGL")]
extern {}

// ------------------------------------------------------------------------------------------------
// EGL 1.0
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_0")]
mod egl1_0 {
	use super::*;

	pub type Boolean = c_uint;
	pub type Int = i32;
	pub type Attrib = usize;
	pub type EGLDisplay = *mut c_void;
	pub type EGLConfig = *mut c_void;
	pub type EGLContext = *mut c_void;
	pub type EGLSurface = *mut c_void;
	pub type NativeDisplayType = *mut c_void;

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Display(pub(crate) EGLDisplay);

	impl Display {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLDisplay) -> Display {
			Display(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLDisplay {
			self.0
		}
	}

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Config(pub(crate) EGLConfig);

	impl Config {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLConfig) -> Config {
			Config(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLConfig {
			self.0
		}
	}

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Context(pub(crate) EGLContext);

	impl Context {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLContext) -> Context {
			Context(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLContext {
			self.0
		}
	}

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Surface(pub(crate) EGLSurface);

	impl Surface {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLSurface) -> Surface {
			Surface(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLSurface {
			self.0
		}
	}

	#[cfg(not(android))]
	pub type NativePixmapType = *mut c_void;

	#[cfg(not(android))]
	pub type NativeWindowType = *mut c_void;

	#[repr(C)]
	#[cfg(android)]
	struct android_native_window_t;

	#[repr(C)]
	#[cfg(android)]
	struct egl_native_pixmap_t;

	#[cfg(android)]
	pub type NativePixmapType = *mut egl_native_pixmap_t;

	#[cfg(android)]
	pub type NativeWindowType = *mut android_native_window_t;

	pub const ALPHA_SIZE: Int = 0x3021;
	pub const BAD_ACCESS: Int = 0x3002;
	pub const BAD_ALLOC: Int = 0x3003;
	pub const BAD_ATTRIBUTE: Int = 0x3004;
	pub const BAD_CONFIG: Int = 0x3005;
	pub const BAD_CONTEXT: Int = 0x3006;
	pub const BAD_CURRENT_SURFACE: Int = 0x3007;
	pub const BAD_DISPLAY: Int = 0x3008;
	pub const BAD_MATCH: Int = 0x3009;
	pub const BAD_NATIVE_PIXMAP: Int = 0x300A;
	pub const BAD_NATIVE_WINDOW: Int = 0x300B;
	pub const BAD_PARAMETER: Int = 0x300C;
	pub const BAD_SURFACE: Int = 0x300D;
	pub const BLUE_SIZE: Int = 0x3022;
	pub const BUFFER_SIZE: Int = 0x3020;
	pub const CONFIG_CAVEAT: Int = 0x3027;
	pub const CONFIG_ID: Int = 0x3028;
	pub const CORE_NATIVE_ENGINE: Int = 0x305B;
	pub const DEPTH_SIZE: Int = 0x3025;
	pub const DONT_CARE: Int = -1;
	pub const DRAW: Int = 0x3059;
	pub const EXTENSIONS: Int = 0x3055;
	pub const FALSE: Boolean = 0;
	pub const GREEN_SIZE: Int = 0x3023;
	pub const HEIGHT: Int = 0x3056;
	pub const LARGEST_PBUFFER: Int = 0x3058;
	pub const LEVEL: Int = 0x3029;
	pub const MAX_PBUFFER_HEIGHT: Int = 0x302A;
	pub const MAX_PBUFFER_PIXELS: Int = 0x302B;
	pub const MAX_PBUFFER_WIDTH: Int = 0x302C;
	pub const NATIVE_RENDERABLE: Int = 0x302D;
	pub const NATIVE_VISUAL_ID: Int = 0x302E;
	pub const NATIVE_VISUAL_TYPE: Int = 0x302F;
	pub const NONE: Int = 0x3038;
	pub const ATTRIB_NONE: Attrib = 0x3038;
	pub const NON_CONFORMANT_CONFIG: Int = 0x3051;
	pub const NOT_INITIALIZED: Int = 0x3001;
	pub const NO_CONTEXT: EGLContext = 0 as EGLContext;
	pub const NO_DISPLAY: EGLDisplay = 0 as EGLDisplay;
	pub const NO_SURFACE: EGLSurface = 0 as EGLSurface;
	pub const PBUFFER_BIT: Int = 0x0001;
	pub const PIXMAP_BIT: Int = 0x0002;
	pub const READ: Int = 0x305A;
	pub const RED_SIZE: Int = 0x3024;
	pub const SAMPLES: Int = 0x3031;
	pub const SAMPLE_BUFFERS: Int = 0x3032;
	pub const SLOW_CONFIG: Int = 0x3050;
	pub const STENCIL_SIZE: Int = 0x3026;
	pub const SUCCESS: Int = 0x3000;
	pub const SURFACE_TYPE: Int = 0x3033;
	pub const TRANSPARENT_BLUE_VALUE: Int = 0x3035;
	pub const TRANSPARENT_GREEN_VALUE: Int = 0x3036;
	pub const TRANSPARENT_RED_VALUE: Int = 0x3037;
	pub const TRANSPARENT_RGB: Int = 0x3052;
	pub const TRANSPARENT_TYPE: Int = 0x3034;
	pub const TRUE: Boolean = 1;
	pub const VENDOR: Int = 0x3053;
	pub const VERSION: Int = 0x3054;
	pub const WIDTH: Int = 0x3057;
	pub const WINDOW_BIT: Int = 0x0004;

	/// EGL errors.
	#[derive(Clone, Copy, PartialEq, Eq, Debug)]
	pub enum Error {
		/// EGL is not initialized, or could not be initialized, for the specified
		/// EGL display connection.
		NotInitialized,

		/// EGL cannot access a requested resource (for example a context is bound
		/// in another thread).
		BadAccess,

		/// EGL failed to allocate resources for the requested operation.
		BadAlloc,

		/// An unrecognized attribute or attribute value was passed in the attribute
		/// list.
		BadAttribute,

		/// An Context argument does not name a valid EGL rendering context.
		BadContext,

		/// An Config argument does not name a valid EGL frame buffer configuration.
		BadConfig,

		/// The current surface of the calling thread is a window, pixel buffer or
		/// pixmap that is no longer valid.
		BadCurrentSurface,

		/// An Display argument does not name a valid EGL display connection.
		BadDisplay,

		/// An Surface argument does not name a valid surface (window, pixel buffer
		/// or pixmap) configured for GL rendering.
		BadSurface,

		/// Arguments are inconsistent (for example, a valid context requires
		/// buffers not supplied by a valid surface).
		BadMatch,

		/// One or more argument values are invalid.
		BadParameter,

		/// A NativePixmapType argument does not refer to a valid native pixmap.
		BadNativePixmap,

		/// A NativeWindowType argument does not refer to a valid native window.
		BadNativeWindow,

		/// A power management event has occurred. The application must destroy all
		/// contexts and reinitialise OpenGL ES state and objects to continue
		/// rendering.
		ContextLost,
	}

	impl std::error::Error for Error {
		fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
			None
		}
	}

	impl Error {
		pub fn native(&self) -> Int {
			use Error::*;
			match self {
				NotInitialized => NOT_INITIALIZED,
				BadAccess => BAD_ACCESS,
				BadAlloc => BAD_ALLOC,
				BadAttribute => BAD_ATTRIBUTE,
				BadContext => BAD_CONTEXT,
				BadConfig => BAD_CONFIG,
				BadCurrentSurface => BAD_CURRENT_SURFACE,
				BadDisplay => BAD_DISPLAY,
				BadSurface => BAD_SURFACE,
				BadMatch => BAD_MATCH,
				BadParameter => BAD_PARAMETER,
				BadNativePixmap => BAD_NATIVE_PIXMAP,
				BadNativeWindow => BAD_NATIVE_WINDOW,
				ContextLost => CONTEXT_LOST,
			}
		}

		fn message(&self) -> &'static str {
			use Error::*;
			match self {
				NotInitialized => "EGL is not initialized, or could not be initialized, for the specified EGL display connection.",
				BadAccess => "EGL cannot access a requested resource (for example a context is bound in another thread.",
				BadAlloc => "EGL failed to allocate resources for the requested operation.",
				BadAttribute => "An unrecognized attribute or attribute value was passed in the attribute list.",
				BadContext => "An Context argument does not name a valid EGL rendering context.",
				BadConfig => "An Config argument does not name a valid EGL frame buffer configuration.",
				BadCurrentSurface => "The current surface of the calling thread is a window, pixel buffer or pixmap that is no longer valid.",
				BadDisplay => "An Display argument does not name a valid EGL display connection.",
				BadSurface => "An Surface argument does not name a valid surface (window, pixel buffer or pixmap) configured for GL rendering.",
				BadMatch => "Arguments are inconsistent (for example, a valid context requires buffers not supplied by a valid surface.",
				BadParameter => "One or more argument values are invalid.",
				BadNativePixmap => "A NativePixmapType argument does not refer to a valid native pixmap.",
				BadNativeWindow => "A NativeWindowType argument does not refer to a valid native window.",
				ContextLost => "A power management event has occurred. The application must destroy all contexts and reinitialise OpenGL ES state and objects to continue rendering."
			}
		}
	}

	impl From<Error> for Int {
		fn from(e: Error) -> Int {
			e.native()
		}
	}

	impl TryFrom<Int> for Error {
		type Error = Int;

		fn try_from(e: Int) -> Result<Error, Int> {
			use Error::*;
			match e {
				NOT_INITIALIZED => Ok(NotInitialized),
				BAD_ACCESS => Ok(BadAccess),
				BAD_ALLOC => Ok(BadAlloc),
				BAD_ATTRIBUTE => Ok(BadAttribute),
				BAD_CONTEXT => Ok(BadContext),
				BAD_CONFIG => Ok(BadConfig),
				BAD_CURRENT_SURFACE => Ok(BadCurrentSurface),
				BAD_DISPLAY => Ok(BadDisplay),
				BAD_SURFACE => Ok(BadSurface),
				BAD_MATCH => Ok(BadMatch),
				BAD_PARAMETER => Ok(BadParameter),
				BAD_NATIVE_PIXMAP => Ok(BadNativePixmap),
				BAD_NATIVE_WINDOW => Ok(BadNativeWindow),
				CONTEXT_LOST => Ok(ContextLost),
				_ => Err(e),
			}
		}
	}

	impl fmt::Display for Error {
		fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
			self.message().fmt(f)
		}
	}

	pub fn check_int_list(attrib_list: &[Int]) -> Result<(), Error> {
		if attrib_list.last() == Some(&NONE) {
			Ok(())
		} else {
			Err(Error::BadParameter)
		}
	}

	pub fn check_attrib_list(attrib_list: &[Attrib]) -> Result<(), Error> {
		if attrib_list.last() == Some(&ATTRIB_NONE) {
			Ok(())
		} else {
			Err(Error::BadParameter)
		}
	}

	impl<T: api::EGL1_0> Instance<T> {
		/// Return the number of EGL frame buffer configurations that atch specified
		/// attributes.
		///
		/// This will call `eglChooseConfig` without `null` as `configs` to get the
		/// number of matching configurations.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		pub fn matching_config_count(&self, display: Display, attrib_list: &[Int]) -> Result<usize, Error> {
			check_int_list(attrib_list)?;
			unsafe {
				let mut count = 0;

				if self.api.eglChooseConfig(
					display.as_ptr(),
					attrib_list.as_ptr(),
					ptr::null_mut(),
					0,
					&mut count,
				) == TRUE
				{
					Ok(count as usize)
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return a list of EGL frame buffer configurations that match specified
		/// attributes.
		///
		/// This will write as many matching configurations in `configs` up to its
		/// capacity. You can use the function [`matching_config_count`](Self::matching_config_count) to get the
		/// exact number of configurations matching the specified attributes.
		///
		/// ## Example
		///
		/// ```
		/// # extern crate khronos_egl as egl;
		/// # extern crate wayland_client;
		/// # fn main() -> Result<(), egl::Error> {
		/// # let egl = egl::Instance::new(egl::Static);
		/// # let wayland_display = wayland_client::Display::connect_to_env().expect("unable to connect to the wayland server");
		/// # let display = egl.get_display(wayland_display.get_display_ptr() as *mut std::ffi::c_void).unwrap();
		/// # egl.initialize(display)?;
		/// # let attrib_list = [egl::RED_SIZE, 8, egl::GREEN_SIZE, 8, egl::BLUE_SIZE, 8, egl::NONE];
		/// // Get the number of matching configurations.
		/// let count = egl.matching_config_count(display, &attrib_list)?;
		///
		/// // Get the matching configurations.
		/// let mut configs = Vec::with_capacity(count);
		/// egl.choose_config(display, &attrib_list, &mut configs)?;
		/// # Ok(())
		/// # }
		/// ```
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		pub fn choose_config(&self, display: Display, attrib_list: &[Int], configs: &mut Vec<Config>) -> Result<(), Error> {
			check_int_list(attrib_list)?;
			unsafe {
				let capacity = configs.capacity();
				let mut count = 0;

				if self.api.eglChooseConfig(
					display.as_ptr(),
					attrib_list.as_ptr(),
					configs.as_mut_ptr() as *mut EGLConfig,
					capacity.try_into().unwrap(),
					&mut count,
				) == TRUE
				{
					configs.set_len(count as usize);
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return the first EGL frame buffer configuration that match specified
		/// attributes.
		///
		/// This is an helper function that will call `choose_config` with a buffer of
		/// size 1, which is equivalent to:
		/// ```
		/// # extern crate khronos_egl as egl;
		/// # extern crate wayland_client;
		/// # fn main() -> Result<(), egl::Error> {
		/// # let egl = egl::Instance::new(egl::Static);
		/// # let wayland_display = wayland_client::Display::connect_to_env().expect("unable to connect to the wayland server");
		/// # let display = egl.get_display(wayland_display.get_display_ptr() as *mut std::ffi::c_void).unwrap();
		/// # egl.initialize(display)?;
		/// # let attrib_list = [egl::RED_SIZE, 8, egl::GREEN_SIZE, 8, egl::BLUE_SIZE, 8, egl::NONE];
		/// let mut configs = Vec::with_capacity(1);
		/// egl.choose_config(display, &attrib_list, &mut configs)?;
		/// configs.first();
		/// # Ok(())
		/// # }
		/// ```
		pub fn choose_first_config(&self, display: Display, attrib_list: &[Int]) -> Result<Option<Config>, Error> {
			let mut configs = Vec::with_capacity(1);
			self.choose_config(display, attrib_list, &mut configs)?;
			Ok(configs.first().map(|config| *config))
		}

		/// Copy EGL surface color buffer to a native pixmap.
		pub fn copy_buffers(&self, display: Display, surface: Surface, target: NativePixmapType) -> Result<(), Error> {
			unsafe {
				if self.api.eglCopyBuffers(display.as_ptr(), surface.as_ptr(), target) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Create a new EGL rendering context.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		pub fn create_context(&self, display: Display, config: Config, share_context: Option<Context>, attrib_list: &[Int]) -> Result<Context, Error> {
			check_int_list(attrib_list)?;
			unsafe {
				let share_context = match share_context {
					Some(share_context) => share_context.as_ptr(),
					None => NO_CONTEXT,
				};

				let context = self.api.eglCreateContext(
					display.as_ptr(),
					config.as_ptr(),
					share_context,
					attrib_list.as_ptr(),
				);

				if context != NO_CONTEXT {
					Ok(Context(context))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Create a new EGL pixel buffer surface.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		pub fn create_pbuffer_surface(&self, display: Display, config: Config, attrib_list: &[Int]) -> Result<Surface, Error> {
			check_int_list(attrib_list)?;
			unsafe {
				let surface =
					self.api.eglCreatePbufferSurface(display.as_ptr(), config.as_ptr(), attrib_list.as_ptr());

				if surface != NO_SURFACE {
					Ok(Surface(surface))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Create a new EGL offscreen surface.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		///
		/// Since this function may raise undefined behavior if the display and native
		/// pixmap do not belong to the same platform, it is inherently unsafe.
		pub unsafe fn create_pixmap_surface(&self, display: Display, config: Config, pixmap: NativePixmapType, attrib_list: &[Int]) -> Result<Surface, Error> {
			check_int_list(attrib_list)?;
			let surface = self.api.eglCreatePixmapSurface(
				display.as_ptr(),
				config.as_ptr(),
				pixmap,
				attrib_list.as_ptr(),
			);

			if surface != NO_SURFACE {
				Ok(Surface(surface))
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Create a new EGL window surface.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		///
		/// Since this function may raise undefined behavior if the display and native
		/// window do not belong to the same platform, it is inherently unsafe.
		pub unsafe fn create_window_surface(&self, display: Display, config: Config, window: NativeWindowType, attrib_list: Option<&[Int]>) -> Result<Surface, Error> {
			let attrib_list = match attrib_list {
				Some(attrib_list) => {
					check_int_list(attrib_list)?;
					attrib_list.as_ptr()
				}
				None => ptr::null(),
			};

			let surface =
				self.api.eglCreateWindowSurface(display.as_ptr(), config.as_ptr(), window, attrib_list);

			if surface != NO_SURFACE {
				Ok(Surface(surface))
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Destroy an EGL rendering context.
		pub fn destroy_context(&self, display: Display, ctx: Context) -> Result<(), Error> {
			unsafe {
				if self.api.eglDestroyContext(display.as_ptr(), ctx.as_ptr()) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Destroy an EGL surface.
		pub fn destroy_surface(&self, display: Display, surface: Surface) -> Result<(), Error> {
			unsafe {
				if self.api.eglDestroySurface(display.as_ptr(), surface.as_ptr()) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return information about an EGL frame buffer configuration.
		pub fn get_config_attrib(&self, display: Display, config: Config, attribute: Int) -> Result<Int, Error> {
			unsafe {
				let mut value: Int = 0;
				if self.api.eglGetConfigAttrib(display.as_ptr(), config.as_ptr(), attribute, &mut value) == TRUE
				{
					Ok(value)
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return the number of all frame buffer configurations.
		///
		/// You can use it to setup the correct capacity for the configurations buffer in [`get_configs`](Self::get_configs).
		///
		/// ## Example
		/// ```
		/// # extern crate khronos_egl as egl;
		/// # extern crate wayland_client;
		/// # fn main() -> Result<(), egl::Error> {
		/// # let egl = egl::Instance::new(egl::Static);
		/// # let wayland_display = wayland_client::Display::connect_to_env().expect("unable to connect to the wayland server");
		/// # let display = egl.get_display(wayland_display.get_display_ptr() as *mut std::ffi::c_void).unwrap();
		/// # egl.initialize(display)?;
		/// let mut configs = Vec::with_capacity(egl.get_config_count(display)?);
		/// egl.get_configs(display, &mut configs);
		/// assert!(configs.len() > 0);
		/// # Ok(())
		/// # }
		/// ```
		pub fn get_config_count(&self, display: Display) -> Result<usize, Error> {
			unsafe {
				let mut count = 0;

				if self.api.eglGetConfigs(display.as_ptr(), std::ptr::null_mut(), 0, &mut count) == TRUE {
					Ok(count as usize)
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Get the list of all EGL frame buffer configurations for a display.
		///
		/// The configurations are added to the `configs` buffer, up to the buffer's capacity.
		/// You can use [`get_config_count`](Self::get_config_count) to get the total number of available frame buffer configurations,
		/// and setup the buffer's capacity accordingly.
		///
		/// ## Example
		/// ```
		/// # extern crate khronos_egl as egl;
		/// # extern crate wayland_client;
		/// # fn main() -> Result<(), egl::Error> {
		/// # let egl = egl::Instance::new(egl::Static);
		/// # let wayland_display = wayland_client::Display::connect_to_env().expect("unable to connect to the wayland server");
		/// # let display = egl.get_display(wayland_display.get_display_ptr() as *mut std::ffi::c_void).unwrap();
		/// # egl.initialize(display)?;
		/// let mut configs = Vec::with_capacity(egl.get_config_count(display)?);
		/// egl.get_configs(display, &mut configs);
		/// # Ok(())
		/// # }
		/// ```
		pub fn get_configs(&self, display: Display, configs: &mut Vec<Config>) -> Result<(), Error> {
			unsafe {
				let capacity = configs.capacity();
				let mut count = 0;

				if self.api.eglGetConfigs(
					display.as_ptr(),
					configs.as_mut_ptr() as *mut EGLConfig,
					capacity.try_into().unwrap(),
					&mut count,
				) == TRUE
				{
					configs.set_len(count as usize);
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return the display for the current EGL rendering context.
		pub fn get_current_display(&self) -> Option<Display> {
			unsafe {
				let display = self.api.eglGetCurrentDisplay();

				if display != NO_DISPLAY {
					Some(Display(display))
				} else {
					None
				}
			}
		}

		/// Return the read or draw surface for the current EGL rendering context.
		pub fn get_current_surface(&self, readdraw: Int) -> Option<Surface> {
			unsafe {
				let surface = self.api.eglGetCurrentSurface(readdraw);

				if surface != NO_SURFACE {
					Some(Surface(surface))
				} else {
					None
				}
			}
		}

		/// Return an EGL display connection.
		pub fn get_display(&self, display_id: NativeDisplayType) -> Option<Display> {
			unsafe {
				let display = self.api.eglGetDisplay(display_id);

				if display != NO_DISPLAY {
					Some(Display(display))
				} else {
					None
				}
			}
		}

		/// Return error information.
		///
		/// Return the error of the last called EGL function in the current thread, or
		/// `None` if the error is set to `SUCCESS`.
		///
		/// Note that since a call to `eglGetError` sets the error to `SUCCESS`, and
		/// since this function is automatically called by any wrapper function
		/// returning a `Result` when necessary, this function may only return `None`
		/// from the point of view of a user.
		pub fn get_error(&self) -> Option<Error> {
			unsafe {
				let e = self.api.eglGetError();
				if e == SUCCESS {
					None
				} else {
					Some(e.try_into().unwrap())
				}
			}
		}

		/// Return a GL or an EGL extension function.
		pub fn get_proc_address(&self, procname: &str) -> Option<extern "C" fn()> {
			unsafe {
				let string = CString::new(procname).unwrap();

				let addr = self.api.eglGetProcAddress(string.as_ptr());
				if !(addr as *const ()).is_null() {
					Some(addr)
				} else {
					None
				}
			}
		}

		/// Initialize an EGL display connection.
		pub fn initialize(&self, display: Display) -> Result<(Int, Int), Error> {
			unsafe {
				let mut major = 0;
				let mut minor = 0;

				if self.api.eglInitialize(display.as_ptr(), &mut major, &mut minor) == TRUE {
					Ok((major, minor))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Attach an EGL rendering context to EGL surfaces.
		pub fn make_current(&self, display: Display, draw: Option<Surface>, read: Option<Surface>, ctx: Option<Context>) -> Result<(), Error> {
			unsafe {
				let draw = match draw {
					Some(draw) => draw.as_ptr(),
					None => NO_SURFACE,
				};
				let read = match read {
					Some(read) => read.as_ptr(),
					None => NO_SURFACE,
				};
				let ctx = match ctx {
					Some(ctx) => ctx.as_ptr(),
					None => NO_CONTEXT,
				};

				if self.api.eglMakeCurrent(display.as_ptr(), draw, read, ctx) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return EGL rendering context information.
		pub fn query_context(&self, display: Display, ctx: Context, attribute: Int) -> Result<Int, Error> {
			unsafe {
				let mut value = 0;
				if self.api.eglQueryContext(display.as_ptr(), ctx.as_ptr(), attribute, &mut value) == TRUE {
					Ok(value)
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return a string describing properties of the EGL client or of an EGL display
		/// connection.
		pub fn query_string(&self, display: Option<Display>, name: Int) -> Result<&'static CStr, Error> {
			unsafe {
				let display_ptr = match display {
					Some(display) => display.as_ptr(),
					None => NO_DISPLAY
				};

				let c_str = self.api.eglQueryString(display_ptr, name);

				if !c_str.is_null() {
					Ok(CStr::from_ptr(c_str))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return EGL surface information.
		pub fn query_surface(&self, display: Display, surface: Surface, attribute: Int) -> Result<Int, Error> {
			unsafe {
				let mut value = 0;
				if self.api.eglQuerySurface(display.as_ptr(), surface.as_ptr(), attribute, &mut value) == TRUE {
					Ok(value)
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Post EGL surface color buffer to a native window.
		pub fn swap_buffers(&self, display: Display, surface: Surface) -> Result<(), Error> {
			unsafe {
				if self.api.eglSwapBuffers(display.as_ptr(), surface.as_ptr()) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Terminate an EGL display connection.
		pub fn terminate(&self, display: Display) -> Result<(), Error> {
			unsafe {
				if self.api.eglTerminate(display.as_ptr()) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Complete GL execution prior to subsequent native rendering calls.
		pub fn wait_gl(&self) -> Result<(), Error> {
			unsafe {
				if self.api.eglWaitGL() == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Complete native execution prior to subsequent GL rendering calls.
		pub fn wait_native(&self, engine: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglWaitNative(engine) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}
	}
}

#[cfg(feature = "1_0")]
pub use egl1_0::*;

// ------------------------------------------------------------------------------------------------
// EGL 1.1
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_1")]
mod egl1_1 {
	use super::*;

	pub const BACK_BUFFER: Int = 0x3084;
	pub const BIND_TO_TEXTURE_RGB: Int = 0x3039;
	pub const BIND_TO_TEXTURE_RGBA: Int = 0x303A;
	pub const CONTEXT_LOST: Int = 0x300E;
	pub const MIN_SWAP_INTERVAL: Int = 0x303B;
	pub const MAX_SWAP_INTERVAL: Int = 0x303C;
	pub const MIPMAP_TEXTURE: Int = 0x3082;
	pub const MIPMAP_LEVEL: Int = 0x3083;
	pub const NO_TEXTURE: Int = 0x305C;
	pub const TEXTURE_2D: Int = 0x305F;
	pub const TEXTURE_FORMAT: Int = 0x3080;
	pub const TEXTURE_RGB: Int = 0x305D;
	pub const TEXTURE_RGBA: Int = 0x305E;
	pub const TEXTURE_TARGET: Int = 0x3081;

	impl<T: api::EGL1_1> Instance<T> {
		/// Defines a two-dimensional texture image.
		pub fn bind_tex_image(&self, display: Display, surface: Surface, buffer: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglBindTexImage(display.as_ptr(), surface.as_ptr(), buffer) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		///  Releases a color buffer that is being used as a texture.
		pub fn release_tex_image(&self, display: Display, surface: Surface, buffer: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglReleaseTexImage(display.as_ptr(), surface.as_ptr(), buffer) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Set an EGL surface attribute.
		pub fn surface_attrib(&self, display: Display, surface: Surface, attribute: Int, value: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglSurfaceAttrib(display.as_ptr(), surface.as_ptr(), attribute, value) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Specifies the minimum number of video frame periods per buffer swap for the
		/// window associated with the current context.
		pub fn swap_interval(&self, display: Display, interval: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglSwapInterval(display.as_ptr(), interval) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}
	}
}

#[cfg(feature = "1_1")]
pub use egl1_1::*;

// ------------------------------------------------------------------------------------------------
// EGL 1.2
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_2")]
mod egl1_2 {
	use super::*;

	pub type Enum = c_uint;
	pub type EGLClientBuffer = *mut c_void;

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct ClientBuffer(EGLClientBuffer);

	impl ClientBuffer {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLClientBuffer) -> ClientBuffer {
			ClientBuffer(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLClientBuffer {
			self.0
		}
	}

	pub const ALPHA_FORMAT: Int = 0x3088;
	pub const ALPHA_FORMAT_NONPRE: Int = 0x308B;
	pub const ALPHA_FORMAT_PRE: Int = 0x308C;
	pub const ALPHA_MASK_SIZE: Int = 0x303E;
	pub const BUFFER_PRESERVED: Int = 0x3094;
	pub const BUFFER_DESTROYED: Int = 0x3095;
	pub const CLIENT_APIS: Int = 0x308D;
	pub const COLORSPACE: Int = 0x3087;
	pub const COLORSPACE_sRGB: Int = 0x3089;
	pub const COLORSPACE_LINEAR: Int = 0x308A;
	pub const COLOR_BUFFER_TYPE: Int = 0x303F;
	pub const CONTEXT_CLIENT_TYPE: Int = 0x3097;
	pub const DISPLAY_SCALING: Int = 10000;
	pub const HORIZONTAL_RESOLUTION: Int = 0x3090;
	pub const LUMINANCE_BUFFER: Int = 0x308F;
	pub const LUMINANCE_SIZE: Int = 0x303D;
	pub const OPENGL_ES_BIT: Int = 0x0001;
	pub const OPENVG_BIT: Int = 0x0002;
	pub const OPENGL_ES_API: Enum = 0x30A0;
	pub const OPENVG_API: Enum = 0x30A1;
	pub const OPENVG_IMAGE: Int = 0x3096;
	pub const PIXEL_ASPECT_RATIO: Int = 0x3092;
	pub const RENDERABLE_TYPE: Int = 0x3040;
	pub const RENDER_BUFFER: Int = 0x3086;
	pub const RGB_BUFFER: Int = 0x308E;
	pub const SINGLE_BUFFER: Int = 0x3085;
	pub const SWAP_BEHAVIOR: Int = 0x3093;
	pub const UNKNOWN: Int = -1;
	pub const VERTICAL_RESOLUTION: Int = 0x3091;

	impl<T: api::EGL1_2> Instance<T> {
		/// Set the current rendering API.
		pub fn bind_api(&self, api: Enum) -> Result<(), Error> {
			unsafe {
				if self.api.eglBindAPI(api) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Query the current rendering API.
		pub fn query_api(&self) -> Enum {
			unsafe { self.api.eglQueryAPI() }
		}

		/// Create a new EGL pixel buffer surface bound to an OpenVG image.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `NONE`).
		pub fn create_pbuffer_from_client_buffer(&self, display: Display, buffer_type: Enum, buffer: ClientBuffer, config: Config, attrib_list: &[Int]) -> Result<Surface, Error> {
			check_int_list(attrib_list)?;
			unsafe {
				let surface = self.api.eglCreatePbufferFromClientBuffer(
					display.as_ptr(),
					buffer_type,
					buffer.as_ptr(),
					config.as_ptr(),
					attrib_list.as_ptr(),
				);

				if surface != NO_SURFACE {
					Ok(Surface(surface))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Release EGL per-thread state.
		pub fn release_thread(&self) -> Result<(), Error> {
			unsafe {
				if self.api.eglReleaseThread() == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Complete client API execution prior to subsequent native rendering calls.
		pub fn wait_client(&self) -> Result<(), Error> {
			unsafe {
				if self.api.eglWaitClient() == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}
	}
}

#[cfg(feature = "1_2")]
pub use egl1_2::*;

// ------------------------------------------------------------------------------------------------
// EGL 1.3
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_3")]
mod egl1_3 {
	use super::*;

	pub const CONFORMANT: Int = 0x3042;
	pub const CONTEXT_CLIENT_VERSION: Int = 0x3098;
	pub const MATCH_NATIVE_PIXMAP: Int = 0x3041;
	pub const OPENGL_ES2_BIT: Int = 0x0004;
	pub const VG_ALPHA_FORMAT: Int = 0x3088;
	pub const VG_ALPHA_FORMAT_NONPRE: Int = 0x308B;
	pub const VG_ALPHA_FORMAT_PRE: Int = 0x308C;
	pub const VG_ALPHA_FORMAT_PRE_BIT: Int = 0x0040;
	pub const VG_COLORSPACE: Int = 0x3087;
	pub const VG_COLORSPACE_sRGB: Int = 0x3089;
	pub const VG_COLORSPACE_LINEAR: Int = 0x308A;
	pub const VG_COLORSPACE_LINEAR_BIT: Int = 0x0020;
}

#[cfg(feature = "1_3")]
pub use egl1_3::*;

// ------------------------------------------------------------------------------------------------
// EGL 1.4
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_4")]
mod egl1_4 {
	use super::*;

	pub const DEFAULT_DISPLAY: NativeDisplayType = 0 as NativeDisplayType;
	pub const MULTISAMPLE_RESOLVE_BOX_BIT: Int = 0x0200;
	pub const MULTISAMPLE_RESOLVE: Int = 0x3099;
	pub const MULTISAMPLE_RESOLVE_DEFAULT: Int = 0x309A;
	pub const MULTISAMPLE_RESOLVE_BOX: Int = 0x309B;
	pub const OPENGL_API: Enum = 0x30A2;
	pub const OPENGL_BIT: Int = 0x0008;
	pub const SWAP_BEHAVIOR_PRESERVED_BIT: Int = 0x0400;

	impl<T: api::EGL1_4> Instance<T> {
		/// Return the current EGL rendering context.
		pub fn get_current_context(&self) -> Option<Context> {
			unsafe {
				let context = self.api.eglGetCurrentContext();

				if context != NO_CONTEXT {
					Some(Context(context))
				} else {
					None
				}
			}
		}
	}
}

#[cfg(feature = "1_4")]
pub use egl1_4::*;

// ------------------------------------------------------------------------------------------------
// EGL 1.5
// ------------------------------------------------------------------------------------------------

#[cfg(feature = "1_5")]
mod egl1_5 {
	use super::*;

	pub type Time = u64;
	pub type EGLSync = *mut c_void;
	pub type EGLImage = *mut c_void;

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Sync(EGLSync);

	impl Sync {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLSync) -> Sync {
			Sync(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLSync {
			self.0
		}
	}

	#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
	pub struct Image(EGLImage);

	impl Image {
		#[inline]
		pub unsafe fn from_ptr(ptr: EGLImage) -> Image {
			Image(ptr)
		}

		#[inline]
		pub fn as_ptr(&self) -> EGLImage {
			self.0
		}
	}

	pub const CONTEXT_MAJOR_VERSION: Int = 0x3098;
	pub const CONTEXT_MINOR_VERSION: Int = 0x30FB;
	pub const CONTEXT_OPENGL_PROFILE_MASK: Int = 0x30FD;
	pub const CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY: Int = 0x31BD;
	pub const NO_RESET_NOTIFICATION: Int = 0x31BE;
	pub const LOSE_CONTEXT_ON_RESET: Int = 0x31BF;
	pub const CONTEXT_OPENGL_CORE_PROFILE_BIT: Int = 0x00000001;
	pub const CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT: Int = 0x00000002;
	pub const CONTEXT_OPENGL_DEBUG: Int = 0x31B0;
	pub const CONTEXT_OPENGL_FORWARD_COMPATIBLE: Int = 0x31B1;
	pub const CONTEXT_OPENGL_ROBUST_ACCESS: Int = 0x31B2;
	pub const OPENGL_ES3_BIT: Int = 0x00000040;
	pub const CL_EVENT_HANDLE: Int = 0x309C;
	pub const SYNC_CL_EVENT: Int = 0x30FE;
	pub const SYNC_CL_EVENT_COMPLETE: Int = 0x30FF;
	pub const SYNC_PRIOR_COMMANDS_COMPLETE: Int = 0x30F0;
	pub const SYNC_TYPE: Int = 0x30F7;
	pub const SYNC_STATUS: Int = 0x30F1;
	pub const SYNC_CONDITION: Int = 0x30F8;
	pub const SIGNALED: Int = 0x30F2;
	pub const UNSIGNALED: Int = 0x30F3;
	pub const SYNC_FLUSH_COMMANDS_BIT: Int = 0x0001;
	pub const FOREVER: u64 = 0xFFFFFFFFFFFFFFFFu64;
	pub const TIMEOUT_EXPIRED: Int = 0x30F5;
	pub const CONDITION_SATISFIED: Int = 0x30F6;
	pub const NO_SYNC: EGLSync = 0 as EGLSync;
	pub const SYNC_FENCE: Int = 0x30F9;
	pub const GL_COLORSPACE: Int = 0x309D;
	pub const GL_COLORSPACE_SRGB: Int = 0x3089;
	pub const GL_COLORSPACE_LINEAR: Int = 0x308A;
	pub const GL_RENDERBUFFER: Int = 0x30B9;
	pub const GL_TEXTURE_2D: Int = 0x30B1;
	pub const GL_TEXTURE_LEVEL: Int = 0x30BC;
	pub const GL_TEXTURE_3D: Int = 0x30B2;
	pub const GL_TEXTURE_ZOFFSET: Int = 0x30BD;
	pub const GL_TEXTURE_CUBE_MAP_POSITIVE_X: Int = 0x30B3;
	pub const GL_TEXTURE_CUBE_MAP_NEGATIVE_X: Int = 0x30B4;
	pub const GL_TEXTURE_CUBE_MAP_POSITIVE_Y: Int = 0x30B5;
	pub const GL_TEXTURE_CUBE_MAP_NEGATIVE_Y: Int = 0x30B6;
	pub const GL_TEXTURE_CUBE_MAP_POSITIVE_Z: Int = 0x30B7;
	pub const GL_TEXTURE_CUBE_MAP_NEGATIVE_Z: Int = 0x30B8;
	pub const IMAGE_PRESERVED: Int = 0x30D2;
	pub const NO_IMAGE: EGLImage = 0 as EGLImage;

	impl<T: api::EGL1_5> Instance<T> {
		/// Create a new EGL sync object.
		///
		/// Note that the constant `ATTRIB_NONE` which has the type `Attrib` can be used
		/// instead of `NONE` to terminate the attribute list.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `ATTRIB_NONE`).
		///
		/// This function is unsafe: when creating an OpenCL Event Sync Object, passing an invalid event
		/// handle in `attrib_list` may result in undefined behavior up to and including program
		/// termination.
		pub unsafe fn create_sync(&self, display: Display, ty: Enum, attrib_list: &[Attrib]) -> Result<Sync, Error> {
			check_attrib_list(attrib_list)?;
			let sync = self.api.eglCreateSync(display.as_ptr(), ty, attrib_list.as_ptr());
			if sync != NO_SYNC {
				Ok(Sync(sync))
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Destroy a sync object.
		///
		/// This function is unsafe: if display does not match the display passed to eglCreateSync when
		/// sync was created, the behaviour is undefined.
		pub unsafe fn destroy_sync(&self, display: Display, sync: Sync) -> Result<(), Error> {
			if self.api.eglDestroySync(display.as_ptr(), sync.as_ptr()) == TRUE {
				Ok(())
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Wait in the client for a sync object to be signalled.
		///
		/// This function is unsafe: if `display` does not match the [`Display`] passed to [`create_sync`](Self::create_sync)
		/// when `sync` was created, the behaviour is undefined.
		pub unsafe fn client_wait_sync(&self, display: Display, sync: Sync, flags: Int, timeout: Time) -> Result<Int, Error> {
			let status = self.api.eglClientWaitSync(display.as_ptr(), sync.as_ptr(), flags, timeout);
			if status != FALSE as Int {
				Ok(status)
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Return an attribute of a sync object.
		///
		/// This function is unsafe: If `display` does not match the [`Display`] passed to [`create_sync`](Self::create_sync)
		/// when `sync` was created, behaviour is undefined.
		pub unsafe fn get_sync_attrib(&self, display: Display, sync: Sync, attribute: Int) -> Result<Attrib, Error> {
			let mut value = 0;
			if self.api.eglGetSyncAttrib(
				display.as_ptr(),
				sync.as_ptr(),
				attribute,
				&mut value as *mut Attrib,
			) == TRUE
			{
				Ok(value)
			} else {
				Err(self.get_error().unwrap())
			}
		}

		/// Create a new Image object.
		///
		/// Note that the constant `ATTRIB_NONE` which has the type `Attrib` can be used
		/// instead of `NONE` to terminate the attribute list.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `ATTRIB_NONE`).
		pub fn create_image(&self, display: Display, ctx: Context, target: Enum, buffer: ClientBuffer, attrib_list: &[Attrib]) -> Result<Image, Error> {
			check_attrib_list(attrib_list)?;
			unsafe {
				let image = self.api.eglCreateImage(
					display.as_ptr(),
					ctx.as_ptr(),
					target,
					buffer.as_ptr(),
					attrib_list.as_ptr(),
				);
				if image != NO_IMAGE {
					Ok(Image(image))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Destroy an Image object.
		pub fn destroy_image(&self, display: Display, image: Image) -> Result<(), Error> {
			unsafe {
				if self.api.eglDestroyImage(display.as_ptr(), image.as_ptr()) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Return an EGL display connection.
		///
		/// Note that the constant `ATTRIB_NONE` which has the type `Attrib` can be used
		/// instead of `NONE` to terminate the attribute list.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `ATTRIB_NONE`).
		pub fn get_platform_display(&self, platform: Enum, native_display: *mut c_void, attrib_list: &[Attrib]) -> Result<Display, Error> {
			check_attrib_list(attrib_list)?;
			unsafe {
				let display = self.api.eglGetPlatformDisplay(platform, native_display, attrib_list.as_ptr());
				if display != NO_DISPLAY {
					Ok(Display(display))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Create a new EGL on-screen rendering surface.
		///
		/// Note that the constant `ATTRIB_NONE` which has the type `Attrib` can be used
		/// instead of `NONE` to terminate the attribute list.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `ATTRIB_NONE`).
		pub fn create_platform_window_surface(&self, display: Display, config: Config, native_window: *mut c_void, attrib_list: &[Attrib]) -> Result<Surface, Error> {
			check_attrib_list(attrib_list)?;
			unsafe {
				let surface = self.api.eglCreatePlatformWindowSurface(
					display.as_ptr(),
					config.as_ptr(),
					native_window,
					attrib_list.as_ptr(),
				);
				if surface != NO_SURFACE {
					Ok(Surface(surface))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Create a new EGL offscreen surface.
		///
		/// Note that the constant `ATTRIB_NONE` which has the type `Attrib` can be used
		/// instead of `NONE` to terminate the attribute list.
		///
		/// This will return a `BadParameter` error if `attrib_list` is not a valid
		/// attributes list (if it does not terminate with `ATTRIB_NONE`).
		pub fn create_platform_pixmap_surface(&self, display: Display, config: Config, native_pixmap: *mut c_void, attrib_list: &[Attrib]) -> Result<Surface, Error> {
			check_attrib_list(attrib_list)?;
			unsafe {
				let surface = self.api.eglCreatePlatformPixmapSurface(
					display.as_ptr(),
					config.as_ptr(),
					native_pixmap,
					attrib_list.as_ptr(),
				);
				if surface != NO_SURFACE {
					Ok(Surface(surface))
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}

		/// Wait in the server for a sync object to be signalled.
		///
		/// This function is unsafe: if `display` does not match the [`Display`] passed to [`create_sync`](Self::create_sync)
		/// when `sync` was created, the behavior is undefined.
		pub fn wait_sync(&self, display: Display, sync: Sync, flags: Int) -> Result<(), Error> {
			unsafe {
				if self.api.eglWaitSync(display.as_ptr(), sync.as_ptr(), flags) == TRUE {
					Ok(())
				} else {
					Err(self.get_error().unwrap())
				}
			}
		}
	}
}

#[cfg(feature = "1_5")]
pub use egl1_5::*;

// -------------------------------------------------------------------------------------------------
// FFI
// -------------------------------------------------------------------------------------------------

macro_rules! api {
	($($id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* }),*) => {
		#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
		pub enum Version {
			$(
				#[cfg(feature=$version)]
				$id,
			)*
		}

		impl std::fmt::Display for Version {
			fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
				match self {
					$(
						#[cfg(feature=$version)]
						Version::$id => write!(f, $version),
					)*
				}
			}
		}

		pub mod api {
			use super::*;

			api!(@api_traits () () $($id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* })*);
		}

		#[cfg(feature="static")]
		mod ffi {
			use libc::{c_char, c_void};

			use super::{
				Attrib, Boolean, EGLClientBuffer, EGLConfig, EGLContext, EGLDisplay, EGLImage, EGLSurface,
				EGLSync, Enum, Int, NativeDisplayType, NativePixmapType, NativeWindowType, Time,
			};

			$(
				extern "C" {
					$(
						#[cfg(feature=$version)]
						pub fn $name ($($arg : $atype ),* ) -> $rtype ;
					)*
				}
			)*
		}

		#[cfg(feature="static")]
		/// Static EGL API interface.
		///
		/// This type is only available when the `static` feature is enabled,
		/// by statically linking the EGL library at compile time.
		#[derive(Copy, Clone, Debug)]
		pub struct Static;

		#[cfg(feature="static")]
		impl Api for Static {
			#[inline(always)]
			fn version(&self) -> Version {
				LATEST
			}
		}

		#[cfg(feature="static")]
		pub static API: Instance<Static> = Instance::new(Static);

		#[cfg(feature="dynamic")]
		extern crate libloading;

		api!(@dynamic_struct $($id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* })*);
		api!(@api_types () $($id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* })*);
	};
	(@dynamic_struct $($id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* })*) => {
		#[cfg(feature="dynamic")]
		#[derive(Debug)]
		pub enum LoadError<L> {
			/// Something wrong happend while loading the library.
			Library(L),

			/// The provided version does not meet the requirements.
			InvalidVersion {
				provided: Version,
				required: Version
			}
		}

		#[cfg(feature="dynamic")]
		impl<L: std::error::Error + 'static> std::error::Error for LoadError<L> {
			fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
				match self {
					LoadError::Library(l) => Some(l),
					_ => None
				}
			}
		}

		#[cfg(feature="dynamic")]
		impl<L: std::fmt::Display> std::fmt::Display for LoadError<L> {
			fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
				match self {
					LoadError::Library(l) => write!(f, "Load error: {}", l),
					LoadError::InvalidVersion { provided, required } => write!(f, "Invalid EGL API version (required {}, provided {})", required, provided)
				}
			}
		}

		#[cfg(feature="dynamic")]
		struct RawDynamic<L> {
			lib: L,
			version: Version,
			$(
				$(
					#[cfg(feature=$version)]
					$name : std::mem::MaybeUninit<unsafe extern "C" fn($($atype ),*) -> $rtype>,
				)*
			)*
		}

		#[cfg(feature="dynamic")]
		impl<L> RawDynamic<L> {
			#[inline(always)]
			/// Returns the underlying EGL library.
			pub fn library(&self) -> &L {
				&self.lib
			}

			#[inline(always)]
			/// Returns the EGL version.
			pub fn version(&self) -> Version {
				self.version
			}

			#[inline(always)]
			/// Sets the EGL version.
			pub unsafe fn set_version(&mut self, version: Version) {
				self.version = version
			}

			/// Wraps the given library but does not load the symbols.
			pub unsafe fn unloaded(lib: L, version: Version) -> Self {
				RawDynamic {
					lib,
					version,
					$(
						$(
							#[cfg(feature=$version)]
							$name : std::mem::MaybeUninit::uninit(),
						)*
					)*
				}
			}
		}

		#[cfg(feature="dynamic")]
		/// Dynamic EGL API interface.
		///
		/// The first type parameter is the type of the underlying library handle.
		/// The second `Dynamic` type parameter gives the EGL API version provided by the library.
		///
		/// This type is only available when the `dynamic` feature is enabled.
		/// In most cases, you may prefer to directly use the `DynamicInstance` type.
		pub struct Dynamic<L, A> {
			raw: RawDynamic<L>,
			_api_version: std::marker::PhantomData<A>
		}

		#[cfg(feature="dynamic")]
		impl<L, A> Dynamic<L, A> {
			#[inline(always)]
			/// Return the underlying EGL library.
			pub fn library(&self) -> &L {
				self.raw.library()
			}

			/// Returns the provided EGL version.
			pub fn version(&self) -> Version {
				self.raw.version()
			}

			/// Wraps the given library but does not load the symbols.
			pub(crate) unsafe fn unloaded(lib: L, version: Version) -> Self {
				Dynamic {
					raw: RawDynamic::unloaded(lib, version),
					_api_version: std::marker::PhantomData
				}
			}
		}

		#[cfg(feature="dynamic")]
		impl<L, A> Api for Dynamic<L, A> {
			/// Returns the provided EGL version.
			#[inline(always)]
			fn version(&self) -> Version {
				self.version()
			}
		}

		#[cfg(feature="dynamic")]
		#[cfg(feature="1_0")]
		impl<L: std::borrow::Borrow<libloading::Library>> Dynamic<L, EGL1_0> {
			#[inline]
			/// Load the EGL API symbols from the given library.
			///
			/// This will load the most recent API provided by the library,
			/// which is at least EGL 1.0.
			/// You can check what version has actually been loaded using [`Dynamic::version`],
			/// and/or convert to a more recent version using [`try_into`](TryInto::try_into).
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_from(lib: L) -> Result<Dynamic<L, EGL1_0>, libloading::Error> {
				let mut result = Dynamic::unloaded(lib, Version::EGL1_0);

				$(
					match $id::load_from(&mut result.raw) {
						Ok(()) => result.raw.set_version(Version::$id),
						Err(libloading::Error::DlSymUnknown) => {
							if Version::$id == Version::EGL1_0 {
								return Err(libloading::Error::DlSymUnknown) // we require at least EGL 1.0.
							} else {
								return Ok(result)
							}
						},
						Err(libloading::Error::DlSym { desc }) => {
							if Version::$id == Version::EGL1_0 {
								return Err(libloading::Error::DlSym { desc }) // we require at least EGL 1.0.
							} else {
								return Ok(result)
							}
						},
						Err(e) => return Err(e)
					}
				)*

				Ok(result)
			}
		}

		#[cfg(feature="dynamic")]
		#[cfg(feature="1_0")]
		impl<L: std::borrow::Borrow<libloading::Library>> Instance<Dynamic<L, EGL1_0>> {
			#[inline(always)]
			/// Create an EGL instance using the symbols provided by the given library.
			///
			/// The most recent version of EGL provided by the given library is loaded.
			/// You can check what version has actually been loaded using [`Instance::version`],
			/// and/or convert to a more recent version using [`try_into`](TryInto::try_into).
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_from(lib: L) -> Result<Instance<Dynamic<L, EGL1_0>>, libloading::Error> {
				Ok(Instance::new(Dynamic::<L, EGL1_0>::load_from(lib)?))
			}
		}

		#[cfg(feature="dynamic")]
		impl<L, V> Instance<Dynamic<L, V>> {
			/// Cast the API.
			#[inline(always)]
			pub fn downcast<W>(&self) -> &Instance<Dynamic<L, W>> where Instance<Dynamic<L, V>>: Downcast<Instance<Dynamic<L, W>>> {
				Downcast::downcast(self)
			}

			/// Cast the API.
			#[inline(always)]
			pub fn upcast<W>(&self) -> Option<&Instance<Dynamic<L, W>>> where Instance<Dynamic<L, V>>: Upcast<Instance<Dynamic<L, W>>> {
				Upcast::upcast(self)
			}
		}

		#[cfg(feature="dynamic")]
		unsafe impl<L: std::borrow::Borrow<libloading::Library> + Send, A: Send> Send for Dynamic<L, A> {}

		#[cfg(feature="dynamic")]
		unsafe impl<L: std::borrow::Borrow<libloading::Library> + std::marker::Sync, A: std::marker::Sync> std::marker::Sync for Dynamic<L, A> {}

		#[cfg(feature="dynamic")]
		impl<L: std::borrow::Borrow<libloading::Library> + fmt::Debug, A> fmt::Debug for Dynamic<L, A> {
			fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
				write!(f, "Dynamic({:?})", self.library())
			}
		}
	};
	(@api_traits ( ) ( ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* } $($t_id:ident : $t_version:literal { $(fn $t_name:ident ($($t_arg:ident : $t_atype:ty ),* ) -> $t_rtype:ty ;)* })*) => {
		api!(@api_trait ( ) ( ) $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* });
		api!(@api_traits ( $id : $version ) ( : $id ) $($t_id : $t_version { $(fn $t_name ($($t_arg : $t_atype ),* ) -> $t_rtype ;)* })*);
	};
	(@api_traits ( $($pred:ident : $p_version:literal)+ ) ( $($deps:tt)+ ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* } $($t_id:ident : $t_version:literal { $(fn $t_name:ident ($($t_arg:ident : $t_atype:ty ),* ) -> $t_rtype:ty ;)* })*) => {
		api!(@api_trait ( $($pred : $p_version)* ) ( $($deps)* ) $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* });
		api!(@api_traits ( $($pred : $version)* $id : $version ) ( $($deps)* + $id ) $($t_id : $t_version { $(fn $t_name ($($t_arg : $t_atype ),* ) -> $t_rtype ;)* })*);
	};
	(@api_traits ( $($pred:ident : $p_version:literal)* ) ( $($deps:tt)* )) => {
		// nothing
	};
	(@api_trait ( $($pred:ident : $p_version:literal)* ) ( $($deps:tt)* ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* }) => {
		/// EGL API interface.
		///
		/// An implementation of this trait can be used to create an [`Instance`].
		///
		/// This crate provides two implemntation of this trait:
		///  - [`Static`] which is available with the `static` feature enabled,
		///    defined by statically linking to the EGL library at compile time.
		///  - [`Dynamic`] which is available with the `dynamic` feature enabled,
		///    defined by dynamically linking to the EGL library at runtime.
		///    In this case, you may prefer to directly use the `DynamicInstance` type.
		#[cfg(feature=$version)]
		pub unsafe trait $id $($deps)* {
			$(
				unsafe fn $name (&self, $($arg : $atype ),* ) -> $rtype ;
			)*
		}
	};
	(@api_types ( ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* } $($t_id:ident : $t_version:literal { $(fn $t_name:ident ($($t_arg:ident : $t_atype:ty ),* ) -> $t_rtype:ty ;)* })*) => {
		#[cfg(feature="dynamic")]
		$(
			#[cfg(not(feature=$t_version))]
		)*
		#[cfg(feature=$version)]
		/// Latest available EGL version.
		pub type Latest = $id;

		$(
			#[cfg(not(feature=$t_version))]
		)*
		#[cfg(feature=$version)]
		/// Latest available EGL version.
		pub const LATEST: Version = Version::$id;

		api!(@api_type ( ) $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* });
		api!(@api_types ( $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* } ) $($t_id : $t_version { $(fn $t_name ($($t_arg : $t_atype ),* ) -> $t_rtype ;)* })*);
	};
	(@api_types ( $($pred:ident : $p_version:literal { $(fn $p_name:ident ($($p_arg:ident : $p_atype:ty ),* ) -> $p_rtype:ty ;)* })+ ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* } $($t_id:ident : $t_version:literal { $(fn $t_name:ident ($($t_arg:ident : $t_atype:ty ),* ) -> $t_rtype:ty ;)* })*) => {
		#[cfg(feature="dynamic")]
		$(
			#[cfg(not(feature=$t_version))]
		)*
		#[cfg(feature=$version)]
		/// Latest available EGL version.
		pub type Latest = $id;

		$(
			#[cfg(not(feature=$t_version))]
		)*
		#[cfg(feature=$version)]
		/// Latest available EGL version.
		pub const LATEST: Version = Version::$id;

		api!(@api_type ( $($pred : $p_version { $(fn $p_name ($($p_arg : $p_atype ),* ) -> $p_rtype ;)* })* ) $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* });
		api!(@api_types ( $($pred : $p_version { $(fn $p_name ($($p_arg : $p_atype ),* ) -> $p_rtype ;)* })* $id : $version { $(fn $name ($($arg : $atype ),* ) -> $rtype ;)* } ) $($t_id : $t_version { $(fn $t_name ($($t_arg : $t_atype ),* ) -> $t_rtype ;)* })*);
	};
	(@api_types ( $($pred:ident : $p_version:literal { $(fn $p_name:ident ($($p_arg:ident : $p_atype:ty ),* ) -> $p_rtype:ty ;)* })+ ) ) => {
		#[cfg(feature="dynamic")]
		#[cfg(feature="1_0")]
		/// Alias for dynamically linked instances with the latest handled version of EGL.
		pub type DynamicInstance<V = Latest> = Instance<Dynamic<libloading::Library, V>>;

		#[cfg(feature="dynamic")]
		#[cfg(feature="1_0")]
		impl DynamicInstance<EGL1_0> {
			#[inline(always)]
			/// Create an EGL instance by finding and loading a dynamic library with the given filename.
			///
			/// See [`Library::new`](libloading::Library::new)
			/// for more details on how the `filename` argument is used.
			///
			/// On Linux plateforms, the library is loaded with the `RTLD_NODELETE` flag.
			/// See [#14](https://github.com/timothee-haudebourg/khronos-egl/issues/14) for more details.
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_from_filename<P: AsRef<std::ffi::OsStr>>(filename: P) -> Result<DynamicInstance<EGL1_0>, libloading::Error> {
				#[cfg(target_os = "linux")]
				let lib: libloading::Library = {
					// On Linux, load library with `RTLD_NOW | RTLD_NODELETE` to fix a SIGSEGV
					// See https://github.com/timothee-haudebourg/khronos-egl/issues/14 for more details.
					libloading::os::unix::Library::open(Some(filename), 0x2 | 0x1000)?.into()
				};
				#[cfg(not(target_os = "linux"))]
				let lib = libloading::Library::new(filename)?;
				Self::load_from(lib)
			}

			#[inline(always)]
			/// Create an EGL instance by finding and loading the `libEGL.so.1` library.
			///
			/// This is equivalent to `DynamicInstance::load_from_filename("libEGL.so.1")`.
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the found library complies to the EGL API.
			pub unsafe fn load() -> Result<DynamicInstance<EGL1_0>, libloading::Error> {
				Self::load_from_filename("libEGL.so.1")
			}
		}
	};
	(@api_type ( $($pred:ident : $p_version:literal { $(fn $p_name:ident ($($p_arg:ident : $p_atype:ty ),* ) -> $p_rtype:ty ;)* })* ) $id:ident : $version:literal { $(fn $name:ident ($($arg:ident : $atype:ty ),* ) -> $rtype:ty ;)* }) => {
		#[cfg(feature="static")]
		#[cfg(feature=$version)]
		unsafe impl api::$id for Static {
			$(
				#[inline(always)]
				unsafe fn $name(&self, $($arg : $atype),*) -> $rtype {
					ffi::$name($($arg),*)
				}
			)*
		}

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		/// EGL version type.
		///
		/// Used by [`Dynamic`] to statically know the EGL API version provided by the library.
		pub struct $id;

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		impl $id {
			#[allow(unused_variables)]
			unsafe fn load_from<L: std::borrow::Borrow<libloading::Library>>(raw: &mut RawDynamic<L>) -> Result<(), libloading::Error> {
				let lib = raw.lib.borrow();

				$(
					let name = stringify!($name).as_bytes();
					let symbol = lib.get::<unsafe extern "C" fn($($atype ),*) -> $rtype>(name)?;
					let ptr = (&symbol.into_raw().into_raw()) as *const *mut _ as *const unsafe extern "C" fn($($atype ),*) -> $rtype;
					assert!(!ptr.is_null());
					raw.$name = std::mem::MaybeUninit::new(*ptr);
				)*

				Ok(())
			}
		}

		$(
			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			unsafe impl<L: std::borrow::Borrow<libloading::Library>> api::$pred for Dynamic<L, $id> {
				$(
					#[inline(always)]
					unsafe fn $p_name(&self, $($p_arg : $p_atype),*) -> $p_rtype {
						(self.raw.$p_name.assume_init())($($p_arg),*)
					}
				)*
			}
		)*

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		unsafe impl<L: std::borrow::Borrow<libloading::Library>> api::$id for Dynamic<L, $id> {
			$(
				#[inline(always)]
				unsafe fn $name(&self, $($arg : $atype),*) -> $rtype {
					(self.raw.$name.assume_init())($($arg),*)
				}
			)*
		}

		$(
			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> TryFrom<Dynamic<L, $pred>> for Dynamic<L, $id> {
				type Error = Dynamic<L, $pred>;

				fn try_from(other: Dynamic<L, $pred>) -> Result<Self, Dynamic<L, $pred>> {
					if other.version() >= Version::$id {
						Ok(Dynamic {
							raw: other.raw,
							_api_version: std::marker::PhantomData
						})
					} else {
						Err(other)
					}
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> From<Dynamic<L, $id>> for Dynamic<L, $pred> {
				fn from(other: Dynamic<L, $id>) -> Self {
					Dynamic {
						raw: other.raw,
						_api_version: std::marker::PhantomData
					}
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> AsRef<Dynamic<L, $pred>> for Dynamic<L, $id> {
				fn as_ref(&self) -> &Dynamic<L, $pred> {
					unsafe { std::mem::transmute(self) } // this is safe because both types have the same repr.
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> Downcast<Dynamic<L, $pred>> for Dynamic<L, $id> {
				fn downcast(&self) -> &Dynamic<L, $pred> {
					unsafe { std::mem::transmute(self) } // this is safe because both types have the same repr.
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> Downcast<Instance<Dynamic<L, $pred>>> for Instance<Dynamic<L, $id>> {
				fn downcast(&self) -> &Instance<Dynamic<L, $pred>> {
					unsafe { std::mem::transmute(self) } // this is safe because both types have the same repr.
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> Upcast<Dynamic<L, $id>> for Dynamic<L, $pred> {
				fn upcast(&self) -> Option<&Dynamic<L, $id>> {
					if self.version() >= Version::$id {
						Some(unsafe { std::mem::transmute(self) }) // this is safe because both types have the same repr.
					} else {
						None
					}
				}
			}

			#[cfg(feature="dynamic")]
			#[cfg(feature=$version)]
			impl<L: std::borrow::Borrow<libloading::Library>> Upcast<Instance<Dynamic<L, $id>>> for Instance<Dynamic<L, $pred>> {
				fn upcast(&self) -> Option<&Instance<Dynamic<L, $id>>> {
					if self.version() >= Version::$id {
						Some(unsafe { std::mem::transmute(self) }) // this is safe because both types have the same repr.
					} else {
						None
					}
				}
			}
		)*

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		impl<L: std::borrow::Borrow<libloading::Library>> Dynamic<L, $id> {
			#[inline]
			/// Load the EGL API symbols from the given library.
			///
			/// The second `Dynamic` type parameter gives the EGL API version expected to be provided by the library.
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_required(lib: L) -> Result<Dynamic<L, $id>, LoadError<libloading::Error>> {
				match Dynamic::<L, EGL1_0>::load_from(lib) {
					Ok(dynamic) => {
						let provided = dynamic.version();
						match dynamic.try_into() {
							Ok(t) => Ok(t),
							Err(_) => Err(LoadError::InvalidVersion {
								provided,
								required: Version::$id
							})
						}
					},
					Err(e) => Err(LoadError::Library(e))
				}
			}
		}

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		impl<L: std::borrow::Borrow<libloading::Library>> Instance<Dynamic<L, $id>> {
			#[inline(always)]
			/// Create an EGL instance using the symbols provided by the given library.
			/// This function fails if the EGL library does not provide the minimum required version given by the type parameter.
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_required_from(lib: L) -> Result<Instance<Dynamic<L, $id>>, LoadError<libloading::Error>> {
				Ok(Instance::new(Dynamic::<L, $id>::load_required(lib)?))
			}
		}

		#[cfg(feature="dynamic")]
		#[cfg(feature=$version)]
		impl DynamicInstance<$id> {
			#[inline(always)]
			/// Create an EGL instance by finding and loading a dynamic library with the given filename.
			/// This function fails if the EGL library does not provide the minimum required version given by the type parameter.
			///
			/// See [`Library::new`](libloading::Library::new)
			/// for more details on how the `filename` argument is used.
			/// 
			/// On Linux plateforms, the library is loaded with the `RTLD_NODELETE` flag.
			/// See [#14](https://github.com/timothee-haudebourg/khronos-egl/issues/14) for more details.
			/// 
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the input library complies to the EGL API.
			pub unsafe fn load_required_from_filename<P: AsRef<std::ffi::OsStr>>(filename: P) -> Result<DynamicInstance<$id>, LoadError<libloading::Error>> {
				#[cfg(target_os = "linux")]
				let lib: libloading::Library = {
					// On Linux, load library with `RTLD_NOW | RTLD_NODELETE` to fix a SIGSEGV
					// See https://github.com/timothee-haudebourg/khronos-egl/issues/14 for more details.
					libloading::os::unix::Library::open(Some(filename), 0x2 | 0x1000).map_err(LoadError::Library)?.into()
				};
				#[cfg(not(target_os = "linux"))]
				let lib = libloading::Library::new(filename).map_err(LoadError::Library)?;
				Self::load_required_from(lib)
			}

			#[inline(always)]
			/// Create an EGL instance by finding and loading the `libEGL.so.1` library.
			/// This function fails if the EGL library does not provide the minimum required version given by the type parameter.
			///
			/// This is equivalent to `DynamicInstance::load_required_from_filename("libEGL.so.1")`.
			///
			/// ## Safety
			/// This is fundamentally unsafe since there are no guaranties the found library complies to the EGL API.
			pub unsafe fn load_required() -> Result<DynamicInstance<$id>, LoadError<libloading::Error>> {
				Self::load_required_from_filename("libEGL.so.1")
			}
		}
	}
}

api! {
	EGL1_0 : "1_0" {
		fn eglChooseConfig(
			display: EGLDisplay,
			attrib_list: *const Int,
			configs: *mut EGLConfig,
			config_size: Int,
			num_config: *mut Int
		) -> Boolean;
		fn eglCopyBuffers(
			display: EGLDisplay,
			surface: EGLSurface,
			target: NativePixmapType
		) -> Boolean;
		fn eglCreateContext(
			display: EGLDisplay,
			config: EGLConfig,
			share_context: EGLContext,
			attrib_list: *const Int
		) -> EGLContext;
		fn eglCreatePbufferSurface(
			display: EGLDisplay,
			config: EGLConfig,
			attrib_list: *const Int
		) -> EGLSurface;
		fn eglCreatePixmapSurface(
			display: EGLDisplay,
			config: EGLConfig,
			pixmap: NativePixmapType,
			attrib_list: *const Int
		) -> EGLSurface;
		fn eglCreateWindowSurface(
			display: EGLDisplay,
			config: EGLConfig,
			win: NativeWindowType,
			attrib_list: *const Int
		) -> EGLSurface;
		fn eglDestroyContext(display: EGLDisplay, ctx: EGLContext) -> Boolean;
		fn eglDestroySurface(display: EGLDisplay, surface: EGLSurface) -> Boolean;
		fn eglGetConfigAttrib(
			display: EGLDisplay,
			config: EGLConfig,
			attribute: Int,
			value: *mut Int
		) -> Boolean;
		fn eglGetConfigs(
			display: EGLDisplay,
			configs: *mut EGLConfig,
			config_size: Int,
			num_config: *mut Int
		) -> Boolean;
		fn eglGetCurrentDisplay() -> EGLDisplay;
		fn eglGetCurrentSurface(readdraw: Int) -> EGLSurface;
		fn eglGetDisplay(display_id: NativeDisplayType) -> EGLDisplay;
		fn eglGetError() -> Int;
		fn eglGetProcAddress(procname: *const c_char) -> extern "C" fn();
		fn eglInitialize(display: EGLDisplay, major: *mut Int, minor: *mut Int) -> Boolean;
		fn eglMakeCurrent(
			display: EGLDisplay,
			draw: EGLSurface,
			read: EGLSurface,
			ctx: EGLContext
		) -> Boolean;
		fn eglQueryContext(
			display: EGLDisplay,
			ctx: EGLContext,
			attribute: Int,
			value: *mut Int
		) -> Boolean;
		fn eglQueryString(display: EGLDisplay, name: Int) -> *const c_char;
		fn eglQuerySurface(
			display: EGLDisplay,
			surface: EGLSurface,
			attribute: Int,
			value: *mut Int
		) -> Boolean;
		fn eglSwapBuffers(display: EGLDisplay, surface: EGLSurface) -> Boolean;
		fn eglTerminate(display: EGLDisplay) -> Boolean;
		fn eglWaitGL() -> Boolean;
		fn eglWaitNative(engine: Int) -> Boolean;
	},

	EGL1_1 : "1_1" {
		fn eglBindTexImage(display: EGLDisplay, surface: EGLSurface, buffer: Int) -> Boolean;
		fn eglReleaseTexImage(display: EGLDisplay, surface: EGLSurface, buffer: Int) -> Boolean;
		fn eglSurfaceAttrib(
			display: EGLDisplay,
			surface: EGLSurface,
			attribute: Int,
			value: Int
		) -> Boolean;
		fn eglSwapInterval(display: EGLDisplay, interval: Int) -> Boolean;
	},

	EGL1_2 : "1_2" {
		fn eglBindAPI(api: Enum) -> Boolean;
		fn eglQueryAPI() -> Enum;
		fn eglCreatePbufferFromClientBuffer(
			display: EGLDisplay,
			buftype: Enum,
			buffer: EGLClientBuffer,
			config: EGLConfig,
			attrib_list: *const Int
		) -> EGLSurface;
		fn eglReleaseThread() -> Boolean;
		fn eglWaitClient() -> Boolean;
	},

	EGL1_3 : "1_3" {
		// nothing.
	},

	EGL1_4 : "1_4" {
		fn eglGetCurrentContext() -> EGLContext;
	},

	EGL1_5 : "1_5" {
		fn eglCreateSync(display: EGLDisplay, type_: Enum, attrib_list: *const Attrib) -> EGLSync;
		fn eglDestroySync(display: EGLDisplay, sync: EGLSync) -> Boolean;
		fn eglClientWaitSync(display: EGLDisplay, sync: EGLSync, flags: Int, timeout: Time) -> Int;
		fn eglGetSyncAttrib(
			display: EGLDisplay,
			sync: EGLSync,
			attribute: Int,
			value: *mut Attrib
		) -> Boolean;
		fn eglCreateImage(
			display: EGLDisplay,
			ctx: EGLContext,
			target: Enum,
			buffer: EGLClientBuffer,
			attrib_list: *const Attrib
		) -> EGLImage;
		fn eglDestroyImage(display: EGLDisplay, image: EGLImage) -> Boolean;
		fn eglGetPlatformDisplay(
			platform: Enum,
			native_display: *mut c_void,
			attrib_list: *const Attrib
		) -> EGLDisplay;
		fn eglCreatePlatformWindowSurface(
			display: EGLDisplay,
			config: EGLConfig,
			native_window: *mut c_void,
			attrib_list: *const Attrib
		) -> EGLSurface;
		fn eglCreatePlatformPixmapSurface(
			display: EGLDisplay,
			config: EGLConfig,
			native_pixmap: *mut c_void,
			attrib_list: *const Attrib
		) -> EGLSurface;
		fn eglWaitSync(display: EGLDisplay, sync: EGLSync, flags: Int) -> Boolean;
	}
}