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use crate::core::engine::opengl::{GL_ARRAY_BUFFER, GLboolean, GLenum, GLfloat, GLint, GLsizei, GLsizeiptr, GLuint, Vec2, gl_bind_buffer, gl_bind_vertex_array, gl_buffer_data, gl_buffer_data_empty, gl_buffer_sub_data_vec2, gl_delete_buffer, gl_delete_vertex_array, gl_enable_vertex_attrib_array, gl_gen_buffer, gl_gen_vertex_array, gl_vertex_attrib_divisor, gl_vertex_attrib_pointer_float};
#[derive(Debug, Clone)]
pub struct Attribute {
pub location: GLuint,
pub size: GLint,
pub normalize: GLboolean,
pub stride: GLsizei,
offset: GLsizei,
pub divisor: GLuint, // 0 = per-vertex, 1 = per-instance
}
impl Attribute {
pub fn new(
location: u32,
size: i32,
stride_components: usize,
offset_components: usize,
) -> Self {
Self {
location,
size,
normalize: GLboolean::FALSE,
stride: (stride_components * std::mem::size_of::<GLfloat>()) as GLsizei,
offset: (offset_components * std::mem::size_of::<GLfloat>()) as GLsizei,
divisor: 0,
}
}
pub fn instanced_vec2(location: u32) -> Self {
// tightly packed vec2, divisor=1
Self {
location,
size: 2,
normalize: GLboolean::FALSE,
stride: (2 * std::mem::size_of::<GLfloat>()) as GLsizei,
offset: 0,
divisor: 1,
}
}
}
/// A GPU-backed buffer representing a drawable shape or mesh.
///
/// `Geometry` encapsulates the OpenGL resources (such as VAOs and VBOs) and metadata required to render
/// a shape using a specific drawing mode (e.g., triangles, lines).
///
pub struct Geometry {
vao: GLuint,
vbo: GLuint,
vertex_count: i32,
drawing_mode: GLenum,
attributes: Vec<Attribute>,
// NEW
instance_vbo: GLuint,
instance_count: i32,
}
impl Drop for Geometry {
fn drop(&mut self) {
if self.instance_vbo != 0 {
gl_delete_buffer(self.instance_vbo);
}
if self.vbo != 0 {
gl_delete_buffer(self.vbo);
}
if self.vao != 0 {
gl_delete_vertex_array(self.vao);
}
}
}
impl Geometry {
/// Creates a new empty [`Geometry`] object with the specified OpenGL drawing mode.
///
/// This initializes a new Vertex Array Object (VAO) and prepares an empty set of vertex attributes.
/// The geometry is not yet ready for rendering until a Vertex Buffer Object (VBO) and vertex data
/// are assigned.
///
/// # Parameters
/// - `drawing_mode`: The OpenGL drawing mode (e.g., `GL_TRIANGLES`, `GL_LINES`) that determines how
/// the vertex data will be interpreted when rendering.
///
/// # Returns
/// A new, uninitialized [`Geometry`] instance.
///
pub fn new(drawing_mode: GLenum) -> Self {
let vao = gl_gen_vertex_array();
Geometry {
vao,
vbo: 0,
vertex_count: 0,
attributes: Vec::new(),
drawing_mode,
instance_vbo: 0,
instance_count: 0,
}
}
/// Uploads vertex data to the GPU and binds it to this geometry object.
///
/// This method creates a new Vertex Buffer Object (VBO), uploads the provided vertex data,
/// and associates it with the previously created Vertex Array Object (VAO).
///
/// # Parameters
///
/// - `buffer`: A flat slice of vertex attribute data. The data layout must match the expected
/// format for the associated shader (e.g., `[x0, y0, x1, y1, ...]` for 2D positions).
/// - `values_per_vertex`: The number of scalar values that make up one vertex
/// (e.g., `2` for a 2D position, `3` for a 3D position).
///
/// # Notes
///
/// - This method **does not define vertex attribute pointers**. You must call another method
/// (e.g., `add_attribute(...)`) to configure how vertex data is interpreted.
/// - The VAO is unbound after the operation to avoid unintended side effects.
///
pub fn add_buffer(&mut self, buffer: &[GLfloat], values_per_vertex: i32) {
self.vbo = gl_gen_buffer();
self.vertex_count = buffer.len() as i32 / values_per_vertex;
gl_bind_vertex_array(self.vao);
gl_bind_buffer(GL_ARRAY_BUFFER, self.vbo);
gl_buffer_data(GL_ARRAY_BUFFER, buffer);
gl_bind_vertex_array(0);
}
/// Defines a vertex attribute layout for this geometry object.
///
/// This sets up how each vertex's data is interpreted in the currently bound Vertex Array Object (VAO).
/// The attribute configuration specifies the format, stride, and offset for a particular input in the shader.
///
/// # Parameters
///
/// - `attribute`: An [`Attribute`] describing the layout of a single vertex attribute
/// (e.g., position, color, texture coordinate). It includes:
/// - `location`: The attribute index as used in the shader (e.g., `layout(location = 0)`).
/// - `size`: Number of components for this attribute (e.g., 2 for vec2, 3 for vec3).
/// - `normalize`: Whether to normalize the values.
/// - `stride`: Byte offset between consecutive vertices.
/// - `offset`: Byte offset to the start of this attribute within the vertex.
/// # Notes
///
/// - This must be called *after* [Self::add_buffer] has uploaded vertex data.
/// - The VAO is bound during the call and unbound afterward to preserve OpenGL state.
/// - You can call this multiple times to add multiple attributes (e.g., position and color).
pub fn add_vertex_attribute(&mut self, attribute: Attribute) {
gl_bind_vertex_array(self.vao);
gl_enable_vertex_attrib_array(attribute.location);
gl_vertex_attrib_pointer_float(
attribute.location,
attribute.size,
attribute.normalize,
attribute.stride,
attribute.offset,
);
gl_vertex_attrib_divisor(attribute.location, attribute.divisor);
gl_bind_vertex_array(0);
self.attributes.push(attribute);
}
pub fn enable_instancing_xy(&mut self, max_instances: usize) {
if self.instance_vbo == 0 {
self.instance_vbo = gl_gen_buffer();
}
gl_bind_vertex_array(self.vao);
gl_bind_buffer(GL_ARRAY_BUFFER, self.instance_vbo);
// Allocate empty buffer of required capacity (you can also upload a zero slice)
let bytes = (max_instances * 2 * std::mem::size_of::<GLfloat>()) as GLsizei;
crate::core::engine::opengl::gl_buffer_data_empty(GL_ARRAY_BUFFER, bytes as GLsizeiptr); // add this tiny helper in FFI OR upload a zero slice
// Attribute at location=1, vec2, divisor=1
let inst_attr = Attribute::instanced_vec2(1);
gl_enable_vertex_attrib_array(inst_attr.location);
gl_vertex_attrib_pointer_float(
inst_attr.location,
inst_attr.size,
inst_attr.normalize,
inst_attr.stride,
inst_attr.offset,
);
gl_vertex_attrib_divisor(inst_attr.location, 1);
gl_bind_vertex_array(0);
gl_bind_buffer(GL_ARRAY_BUFFER, 0);
}
pub fn update_instance_xy(&mut self, xy: &[Vec2]) {
if self.instance_vbo == 0 { return; }
gl_bind_vertex_array(self.vao);
gl_bind_buffer(GL_ARRAY_BUFFER, self.instance_vbo);
// orphan + upload
let bytes = (xy.len() * std::mem::size_of::<Vec2>()) as GLsizei;
gl_buffer_data_empty(GL_ARRAY_BUFFER, bytes as GLsizeiptr);
gl_buffer_sub_data_vec2(GL_ARRAY_BUFFER, xy);
gl_bind_vertex_array(0);
gl_bind_buffer(GL_ARRAY_BUFFER, 0);
self.instance_count = xy.len() as i32;
}
pub fn clear_instancing(&mut self) {
self.instance_count = 0;
// keep instance_vbo for reuse
}
pub fn instance_count(&self) -> i32 { self.instance_count }
pub fn drawing_mode(&self) -> GLenum {
self.drawing_mode
}
pub fn vertex_count(&self) -> i32 {
self.vertex_count
}
pub fn bind(&self) {
gl_bind_vertex_array(self.vao)
}
pub fn unbind(&self) {
gl_bind_vertex_array(0)
}
}