glium 0.36.0

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 
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/*!

The `backend` module allows one to link between glium and the OpenGL context..

There are three concepts in play:

 - The `Backend` trait describes the glue between glium and the OpenGL context provider like
   glutin, SDL, GLFW, etc.
 - The `Context` struct is the main brick of glium. It manages everything that glium needs to
   execute OpenGL commands. Creating a `Context` requires a `Backend`.
 - The `Facade` trait. Calling functions like `VertexBuffer::new` requires passing an object
   that implements this trait. It is implemented on `Rc<Context>`.

*/
use std::rc::Rc;
use std::ops::Deref;
use std::os::raw::c_void;

use crate::CapabilitiesSource;
use crate::SwapBuffersError;

use crate::context::Capabilities;
use crate::context::ExtensionsList;
use crate::version::Version;

pub use crate::context::Context;
pub use crate::context::ReleaseBehavior;

#[cfg(feature = "glutin")]
pub mod glutin;

#[cfg(feature = "simple_window_builder")]
pub use winit;

/// Trait for types that can be used as a backend for a glium context.
///
/// This trait is unsafe, as you can get undefined behaviors or crashes if you don't implement
/// the methods correctly.
pub unsafe trait Backend {
    /// Swaps buffers at the end of a frame.
    fn swap_buffers(&self) -> Result<(), SwapBuffersError>;

    /// Returns the address of an OpenGL function.
    ///
    /// Supposes that the context has been made current before this function is called.
    unsafe fn get_proc_address(&self, symbol: &str) -> *const c_void;

    /// Returns the dimensions of the window, or screen, etc.
    fn get_framebuffer_dimensions(&self) -> (u32, u32);

    /// Resizes the underlying surface, should be called when the window's size has changed for example.
    fn resize(&self, new_size:(u32, u32));

    /// Returns true if the OpenGL context is the current one in the thread.
    fn is_current(&self) -> bool;

    /// Makes the OpenGL context the current context in the current thread.
    unsafe fn make_current(&self);
}

unsafe impl<T> Backend for Rc<T> where T: Backend {
    fn swap_buffers(&self) -> Result<(), SwapBuffersError> {
        self.deref().swap_buffers()
    }

    unsafe fn get_proc_address(&self, symbol: &str) -> *const c_void {
        self.deref().get_proc_address(symbol)
    }

    fn get_framebuffer_dimensions(&self) -> (u32, u32) {
        self.deref().get_framebuffer_dimensions()
    }

    fn resize(&self, new_size:(u32, u32)) {
        self.deref().resize(new_size);
    }

    fn is_current(&self) -> bool {
        self.deref().is_current()
    }

    unsafe fn make_current(&self) {
        self.deref().make_current();
    }
}

/// Trait for types that provide a safe access for glium functions.
pub trait Facade {
    /// Returns an opaque type that contains the OpenGL state, extensions, version, etc.
    fn get_context(&self) -> &Rc<Context>;
}

impl<T: ?Sized> CapabilitiesSource for T where T: Facade {
    fn get_version(&self) -> &Version {
        self.get_context().deref().get_opengl_version()
    }

    fn get_extensions(&self) -> &ExtensionsList {
        self.get_context().deref().get_extensions()
    }

    fn get_capabilities(&self) -> &Capabilities {
        self.get_context().deref().get_capabilities()
    }
}

impl Facade for Rc<Context> {
    #[inline]
    fn get_context(&self) -> &Rc<Context> {
        self
    }
}