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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 CapabilitiesSource;
use SwapBuffersError;
use context::Capabilities;
use context::ExtensionsList;
use version::Version;
pub use context::Context;
pub use context::ReleaseBehavior;
#[cfg(feature = "glutin")]
pub mod glutin;
/// 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);
/// 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 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_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
}
}