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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/*!
Contains everything related to external API memory objects.
*/

// TODO: Add Windows support via EXT_external_objects_win32

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

use crate::backend::Facade;
use crate::context::Context;
use crate::ContextExt;
use std::rc::Rc;

/// Describes an error encountered during memory object creation
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MemoryObjectCreationError {
    /// Driver does not support EXT_memory_object
    MemoryObjectNotSupported,
    /// Driver does not support EXT_memory_object_fd
    MemoryObjectFdNotSupported,
    /// OpenGL returned a null pointer when creating memory object
    NullResult,
}

impl std::fmt::Display for MemoryObjectCreationError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        use self::MemoryObjectCreationError::*;

        let desc = match *self {
            MemoryObjectNotSupported => "Driver does not support EXT_memory_object",
            MemoryObjectFdNotSupported => "Driver does not support EXT_memory_object_fd",
            NullResult => "OpenGL returned a null pointer when creating memory object",
        };
        f.write_str(desc)
    }
}

impl std::error::Error for MemoryObjectCreationError {}

/// Describes a memory object created by an external API. In OpenGL there is no distinction
/// between a texture or buffer and its underlying memory. However, in other API's like Vulkan
/// the underlying memory and the image are separate. Thus this type is useful when interfacing
/// with such APIs, as such a memory object can then be used to create a texture or buffer
/// which OpenGL can then interact with.
pub struct MemoryObject {
    context: Rc<Context>,
    id: gl::types::GLuint,
}

impl MemoryObject {
    /// Creates a memory object form an opaque file descriptor.
    #[cfg(target_os = "linux")]
    pub unsafe fn new_from_fd<F: Facade + ?Sized>(
        facade: &F,
        dedicated: bool,
        fd: std::fs::File,
        size: u64,
    ) -> Result<Self, MemoryObjectCreationError> {
        use std::os::unix::io::AsRawFd;
        let ctxt = facade.get_context().make_current();
        let mem_obj: Self = Self::new(facade, &ctxt)?;

        if !ctxt.extensions.gl_ext_memory_object_fd {
            Err(MemoryObjectCreationError::MemoryObjectFdNotSupported)
        } else {
            let dedicated: gl::types::GLint = if dedicated {
                gl::TRUE as i32
            } else {
                gl::FALSE as i32
            };

            ctxt.gl.MemoryObjectParameterivEXT(
                mem_obj.id,
                gl::DEDICATED_MEMORY_OBJECT_EXT,
                &dedicated as *const i32,
            );

            ctxt.gl.ImportMemoryFdEXT(
                mem_obj.id,
                size,
                gl::HANDLE_TYPE_OPAQUE_FD_EXT,
                fd.as_raw_fd(),
            );

            std::mem::forget(fd);

            Ok(mem_obj)
        }
    }

    fn new<F: Facade + ?Sized>(
        facade: &F,
        ctxt: &CommandContext<'_>,
    ) -> Result<Self, MemoryObjectCreationError> {
        if (ctxt.version >= &Version(Api::Gl, 4, 5)
            || ctxt.version >= &Version(Api::GlEs, 3, 2)
            || ctxt.extensions.gl_arb_texture_storage)
            && ctxt.extensions.gl_ext_memory_object
        {
            let id = unsafe {
                let mut id: gl::types::GLuint = 0;
                ctxt.gl.CreateMemoryObjectsEXT(1, &mut id as *mut u32);

                if ctxt.gl.IsMemoryObjectEXT(id) == gl::FALSE {
                    return Err(MemoryObjectCreationError::NullResult);
                } else {
                    id
                }
            };

            Ok(Self {
                context: facade.get_context().clone(),
                id,
            })
        } else {
            Err(MemoryObjectCreationError::MemoryObjectNotSupported)
        }
    }
}

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

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

impl Drop for MemoryObject {
    fn drop(&mut self) {
        let ctxt = self.context.get_context().make_current();
        unsafe { ctxt.gl.DeleteMemoryObjectsEXT(1, &mut self.id as *mut u32) };
    }
}