emerald 0.3.214

A lite, fully featured 2D game engine.
Documentation 
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use rapier2d::na::Matrix4;

// lib.rs
#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
pub(crate) struct Vertex {
    pub position: [f32; 2],
    pub tex_coords: [f32; 2],
    pub color: [f32; 4],
}
impl Vertex {
    pub fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
        wgpu::VertexBufferLayout {
            array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 0,
                    format: wgpu::VertexFormat::Float32x2,
                },
                wgpu::VertexAttribute {
                    offset: std::mem::size_of::<[f32; 2]>() as wgpu::BufferAddress,
                    shader_location: 1,
                    format: wgpu::VertexFormat::Float32x2,
                },
                wgpu::VertexAttribute {
                    offset: (std::mem::size_of::<[f32; 2]>() * 2) as wgpu::BufferAddress,
                    shader_location: 2,
                    format: wgpu::VertexFormat::Float32x4,
                },
            ],
        }
    }
}

pub(crate) const VERTICES: &[Vertex] = &[
    // Changed
    Vertex {
        position: [-1.0, 1.0],
        tex_coords: [0.0, 0.0],
        color: [0.0, 0.0, 0.0, 1.0],
    }, // A
    Vertex {
        position: [-1.0, -1.0],
        tex_coords: [0.0, 1.0],
        color: [0.0, 0.0, 0.0, 1.0],
    }, // B
    Vertex {
        position: [1.0, -1.0],
        tex_coords: [1.0, 1.0],
        color: [0.0, 0.0, 0.0, 1.0],
    }, // C
    Vertex {
        position: [1.0, 1.0],
        tex_coords: [1.0, 0.0],
        color: [0.0, 0.0, 0.0, 1.0],
    },
];

pub(crate) const INDICES: &[u16] = &[0, 1, 2, 0, 2, 3];

pub(crate) struct Camera2D {
    pub view_height: u32,
    pub view_width: u32,
}

impl Camera2D {
    pub fn new(view_width: u32, view_height: u32) -> Self {
        Self {
            view_height,
            view_width,
        }
    }

    fn build_view_projection_matrix(&self) -> Matrix4<f32> {
        // // 1.
        // let view = cgmath::Matrix4::look_at_rh(self.eye, self.target, self.up);
        // // 2.
        let proj = Matrix4::new_orthographic(-1.0, 1.0, -1.0, 1.0, 0.0, 100.0);

        // 3.
        return proj;
    }
}

// We need this for Rust to store our data correctly for the shaders
#[repr(C)]
// This is so we can store this in a buffer
#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
pub(crate) struct CameraUniform {
    // We can't use cgmath with bytemuck directly so we'll have
    // to convert the Matrix4 into a 4x4 f32 array
    view_width: f32,
    view_height: f32,
}

impl CameraUniform {
    pub fn new(view_width: f32, view_height: f32) -> Self {
        Self {
            view_height,
            view_width,
        }
    }
}

// Credit(https://github.com/not-fl3/good-web-game/blob/master/src/graphics/image.rs#L129)
// pub(crate) fn param_to_instance_transform(
//     rotation: f32,
//     scale: Vec2,
//     offset: Vec2,
//     dest: Vec2,
// ) -> Mat4 {
//     let cosr = rotation.cos();
//     let sinr = rotation.sin();
//     let m00 = cosr * scale.x;
//     let m01 = -sinr * scale.y;
//     let m10 = sinr * scale.x;
//     let m11 = cosr * scale.y;
//     let m03 = offset.x * (1.0 - m00) - offset.y * m01 + dest.x;
//     let m13 = offset.y * (1.0 - m11) - offset.x * m10 + dest.y;

//     Mat4::from_cols(
//         Vec4::new(m00, m10, 0.0, 0.0),
//         Vec4::new(m01, m11, 0.0, 0.0),
//         Vec4::new(0.0, 0.0, 1.0, 0.0),
//         Vec4::new(m03, m13, 0.0, 1.0),
//     )
// }