Draft first working version of `iced_glow` :tada:

1 files changed, 254 insertions, 0 deletions

diff --git a/glow/src/quad.rs b/glow/src/quad.rs
new file mode 100644
index 00000000..744597d2
--- /dev/null
+++ b/glow/src/quad.rs
@@ -0,0 +1,254 @@
+use crate::{Transformation, Viewport};
+use glow::HasContext;
+use iced_native::Rectangle;
+
+#[derive(Debug)]
+pub struct Pipeline {
+    program: <glow::Context as HasContext>::Program,
+    vertex_array: <glow::Context as HasContext>::VertexArray,
+    instances: <glow::Context as HasContext>::Buffer,
+    current_transform: Transformation,
+    current_scale: f32,
+}
+
+impl Pipeline {
+    pub fn new(gl: &glow::Context) -> Pipeline {
+        let program = unsafe {
+            create_program(
+                gl,
+                &[
+                    (glow::VERTEX_SHADER, include_str!("shader/quad.vert")),
+                    (glow::FRAGMENT_SHADER, include_str!("shader/quad.frag")),
+                ],
+            )
+        };
+
+        unsafe {
+            gl.use_program(Some(program));
+
+            gl.uniform_matrix_4_f32_slice(
+                Some(0),
+                false,
+                &Transformation::identity().into(),
+            );
+            gl.uniform_1_f32(Some(1), 1.0);
+
+            gl.use_program(None);
+        }
+
+        let (vertex_array, instances) =
+            unsafe { create_instance_buffer(gl, Quad::MAX) };
+
+        Pipeline {
+            program,
+            vertex_array,
+            instances,
+            current_transform: Transformation::identity(),
+            current_scale: 1.0,
+        }
+    }
+
+    pub fn draw(
+        &mut self,
+        gl: &glow::Context,
+        viewport: &Viewport,
+        instances: &[Quad],
+        transformation: Transformation,
+        scale: f32,
+        bounds: Rectangle<u32>,
+    ) {
+        unsafe {
+            gl.enable(glow::SCISSOR_TEST);
+            gl.scissor(
+                bounds.x as i32,
+                (viewport.height()
+                    - (bounds.y + bounds.height).min(viewport.height()))
+                    as i32,
+                bounds.width as i32,
+                bounds.height as i32,
+            );
+
+            gl.use_program(Some(self.program));
+            gl.bind_vertex_array(Some(self.vertex_array));
+            gl.bind_buffer(glow::ARRAY_BUFFER, Some(self.instances));
+        }
+
+        if transformation != self.current_transform {
+            unsafe {
+                gl.uniform_matrix_4_f32_slice(
+                    Some(0),
+                    false,
+                    &transformation.into(),
+                );
+
+                self.current_transform = transformation;
+            }
+        }
+
+        if scale != self.current_scale {
+            unsafe {
+                gl.uniform_1_f32(Some(1), scale);
+            }
+
+            self.current_scale = scale;
+        }
+
+        let mut i = 0;
+        let total = instances.len();
+
+        while i < total {
+            let end = (i + Quad::MAX).min(total);
+            let amount = end - i;
+
+            unsafe {
+                gl.buffer_sub_data_u8_slice(
+                    glow::ARRAY_BUFFER,
+                    0,
+                    bytemuck::cast_slice(&instances[i..end]),
+                );
+
+                gl.draw_arrays_instanced(
+                    glow::TRIANGLE_STRIP,
+                    0,
+                    4,
+                    amount as i32,
+                );
+            }
+
+            i += Quad::MAX;
+        }
+
+        unsafe {
+            gl.bind_vertex_array(None);
+            gl.use_program(None);
+            gl.disable(glow::SCISSOR_TEST);
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+#[repr(C)]
+pub struct Quad {
+    pub position: [f32; 2],
+    pub scale: [f32; 2],
+    pub color: [f32; 4],
+    pub border_color: [f32; 4],
+    pub border_radius: f32,
+    pub border_width: f32,
+}
+
+unsafe impl bytemuck::Zeroable for Quad {}
+unsafe impl bytemuck::Pod for Quad {}
+
+impl Quad {
+    const MAX: usize = 100_000;
+}
+
+unsafe fn create_program(
+    gl: &glow::Context,
+    shader_sources: &[(u32, &str)],
+) -> <glow::Context as HasContext>::Program {
+    let program = gl.create_program().expect("Cannot create program");
+
+    let mut shaders = Vec::with_capacity(shader_sources.len());
+
+    for (shader_type, shader_source) in shader_sources.iter() {
+        let shader = gl
+            .create_shader(*shader_type)
+            .expect("Cannot create shader");
+
+        gl.shader_source(shader, shader_source);
+        gl.compile_shader(shader);
+
+        if !gl.get_shader_compile_status(shader) {
+            panic!(gl.get_shader_info_log(shader));
+        }
+
+        gl.attach_shader(program, shader);
+
+        shaders.push(shader);
+    }
+
+    gl.link_program(program);
+    if !gl.get_program_link_status(program) {
+        panic!(gl.get_program_info_log(program));
+    }
+
+    for shader in shaders {
+        gl.detach_shader(program, shader);
+        gl.delete_shader(shader);
+    }
+
+    program
+}
+
+unsafe fn create_instance_buffer(
+    gl: &glow::Context,
+    size: usize,
+) -> (
+    <glow::Context as HasContext>::VertexArray,
+    <glow::Context as HasContext>::Buffer,
+) {
+    let vertex_array = gl.create_vertex_array().expect("Create vertex array");
+    let buffer = gl.create_buffer().expect("Create instance buffer");
+
+    gl.bind_vertex_array(Some(vertex_array));
+    gl.bind_buffer(glow::ARRAY_BUFFER, Some(buffer));
+    gl.buffer_data_size(
+        glow::ARRAY_BUFFER,
+        (size * std::mem::size_of::<Quad>()) as i32,
+        glow::DYNAMIC_DRAW,
+    );
+
+    let stride = std::mem::size_of::<Quad>() as i32;
+
+    gl.enable_vertex_attrib_array(0);
+    gl.vertex_attrib_pointer_f32(0, 2, glow::FLOAT, false, stride, 0);
+    gl.vertex_attrib_divisor(0, 1);
+
+    gl.enable_vertex_attrib_array(1);
+    gl.vertex_attrib_pointer_f32(1, 2, glow::FLOAT, false, stride, 4 * 2);
+    gl.vertex_attrib_divisor(1, 1);
+
+    gl.enable_vertex_attrib_array(2);
+    gl.vertex_attrib_pointer_f32(2, 4, glow::FLOAT, false, stride, 4 * (2 + 2));
+    gl.vertex_attrib_divisor(2, 1);
+
+    gl.enable_vertex_attrib_array(3);
+    gl.vertex_attrib_pointer_f32(
+        3,
+        4,
+        glow::FLOAT,
+        false,
+        stride,
+        4 * (2 + 2 + 4),
+    );
+    gl.vertex_attrib_divisor(3, 1);
+
+    gl.enable_vertex_attrib_array(4);
+    gl.vertex_attrib_pointer_f32(
+        4,
+        1,
+        glow::FLOAT,
+        false,
+        stride,
+        4 * (2 + 2 + 4 + 4),
+    );
+    gl.vertex_attrib_divisor(4, 1);
+
+    gl.enable_vertex_attrib_array(5);
+    gl.vertex_attrib_pointer_f32(
+        5,
+        1,
+        glow::FLOAT,
+        false,
+        stride,
+        4 * (2 + 2 + 4 + 4 + 1),
+    );
+    gl.vertex_attrib_divisor(5, 1);
+
+    gl.bind_vertex_array(None);
+    gl.bind_buffer(glow::ARRAY_BUFFER, None);
+
+    (vertex_array, buffer)
+}