1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166

pub mod prelude {
    pub use super::{VertexArray, VertexArrayDesc};
}

use std::fmt;
use std::marker::PhantomData;

use crate::AttribBinding;

use super::{Attrib, AttribBindPoint, Buffer, GLHandle, RenderingContext};

#[derive(Clone, Debug)]
pub struct VertexArrayDesc<'gl, 'a> {
    buffers: Vec<&'a Buffer<'gl>>,
    bind_points: Vec<AttribBindPoint>,
    bindings: Vec<AttribBinding>,
    attribs: Vec<Attrib>,
}

impl<'gl, 'a> VertexArrayDesc<'gl, 'a> {
    pub fn new() -> Self {
        Self {
            buffers: Vec::new(),
            bind_points: Vec::new(),
            bindings: Vec::new(),
            attribs: Vec::new(),
        }
    }

    pub fn with_buffer(mut self, buffer: &'a Buffer<'gl>) -> Self {
        self.buffers.push(buffer);
        self
    }

    pub fn with_bind_point(mut self, bind_point: AttribBindPoint) -> Self {
        self.bind_points.push(bind_point);
        self
    }

    pub fn with_binding(mut self, binding: AttribBinding) -> Self {
        self.bindings.push(binding);
        self
    }

    pub fn with_attrib(mut self, attrib: Attrib) -> Self {
        self.attribs.push(attrib);
        self
    }

    pub unsafe fn apply(&self, vao: u32) {
        for (buffer_index, bind_point) in self.bind_points.iter().enumerate() {
            let buffer = &self.buffers[buffer_index];
            bind_point.apply(vao, buffer.gl_handle());
        }

        for binding in &self.bindings {
            binding.apply(vao);
        }

        for attrib in &self.attribs {
            attrib.enable(vao);
            attrib.apply(vao);
        }
    }
}

impl<'gl, 'a> AsRef<VertexArrayDesc<'gl, 'a>> for VertexArrayDesc<'gl, 'a> {
    #[inline]
    fn as_ref(&self) -> &VertexArrayDesc<'gl, 'a> {
        self
    }
}

pub struct VertexArray<'gl> {
    handle: u32,
    phantom: PhantomData<&'gl ()>,
}

impl VertexArray<'static> {
    /// # Safety
    ///
    /// Must only be called on a thread where there is a current
    /// OpenGL context. The returned `VertexArray` must only
    /// exist, while the OpenGL context is valid.
    #[inline]
    pub unsafe fn new_unsafe<'gl, 'a>(desc: impl AsRef<VertexArrayDesc<'gl, 'a>>) -> Self
    where
        'gl: 'a,
    {
        let arr = Self::create();
        unsafe {
            desc.as_ref().apply(arr.handle);
        }
        arr
    }
}

impl<'gl> VertexArray<'gl> {
    #[inline]
    pub fn new<'a>(
        _ctx: &mut RenderingContext<'gl>,
        desc: impl AsRef<VertexArrayDesc<'gl, 'a>>,
    ) -> Self
    where
        'gl: 'a,
    {
        let arr = Self::create();
        unsafe {
            desc.as_ref().apply(arr.handle);
        }
        arr
    }

    fn create() -> Self {
        let mut handle = 0;
        unsafe {
            gl::CreateVertexArrays(1, &mut handle);
        }
        debug_assert_ne!(handle, 0, "failed creating vertex array");
        Self {
            handle,
            phantom: PhantomData,
        }
    }

    #[inline]
    pub unsafe fn bind(&self) {
        gl::BindVertexArray(self.handle);
    }

    #[inline]
    pub unsafe fn draw_triangles(&self, first: u32, tri_count: u32) {
        self.draw_arrays(gl::TRIANGLES, first * 3, tri_count * 3);
    }

    #[inline]
    pub unsafe fn draw_points(&self, first: u32, vertex_count: u32) {
        self.draw_arrays(gl::POINTS, first, vertex_count);
    }

    #[inline]
    unsafe fn draw_arrays(&self, mode: u32, first: u32, vertex_count: u32) {
        gl::DrawArrays(mode, first as i32, vertex_count as i32);
    }
}

impl GLHandle for VertexArray<'_> {
    #[inline]
    unsafe fn gl_handle(&self) -> u32 {
        self.handle
    }
}

impl Drop for VertexArray<'_> {
    fn drop(&mut self) {
        unsafe {
            gl::DeleteVertexArrays(1, &self.handle);
        }
    }
}

impl fmt::Debug for VertexArray<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "VertexArray({})", self.handle)
    }
}