0403948aa2
# Background In `no_std` compatible crates, there is often an `std` feature which will allow access to the standard library. Currently, with the `std` feature _enabled_, the [`std::prelude`](https://doc.rust-lang.org/std/prelude/index.html) is implicitly imported in all modules. With the feature _disabled_, instead the [`core::prelude`](https://doc.rust-lang.org/core/prelude/index.html) is implicitly imported. This creates a subtle and pervasive issue where `alloc` items _may_ be implicitly included (if `std` is enabled), or must be explicitly included (if `std` is not enabled). # Objective - Make the implicit imports for `no_std` crates consistent regardless of what features are/not enabled. ## Solution - Replace the `cfg_attr` "double negative" `no_std` attribute with conditional compilation to _include_ `std` as an external crate. ```rust // Before #![cfg_attr(not(feature = "std"), no_std)] // After #![no_std] #[cfg(feature = "std")] extern crate std; ``` - Fix imports that are currently broken but are only now visible with the above fix. ## Testing - CI ## Notes I had previously used the "double negative" version of `no_std` based on general consensus that it was "cleaner" within the Rust embedded community. However, this implicit prelude issue likely was considered when forming this consensus. I believe the reason why is the items most affected by this issue are provided by the `alloc` crate, which is rarely used within embedded but extensively used within Bevy.
105 lines
3.2 KiB
Rust
105 lines
3.2 KiB
Rust
#![allow(
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unsafe_op_in_unsafe_fn,
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clippy::all,
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clippy::undocumented_unsafe_blocks,
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clippy::ptr_cast_constness,
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// FIXME(15321): solve CI failures, then replace with `#![expect()]`.
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missing_docs
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)]
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#![cfg_attr(docsrs, feature(doc_auto_cfg))]
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#![doc(
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html_logo_url = "https://bevyengine.org/assets/icon.png",
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html_favicon_url = "https://bevyengine.org/assets/icon.png"
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)]
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#![no_std]
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#[cfg(feature = "std")]
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extern crate std;
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extern crate alloc;
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use glam::{Vec2, Vec3};
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mod generated;
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/// The interface by which mikktspace interacts with your geometry.
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pub trait Geometry {
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/// Returns the number of faces.
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fn num_faces(&self) -> usize;
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/// Returns the number of vertices of a face.
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fn num_vertices_of_face(&self, face: usize) -> usize;
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/// Returns the position of a vertex.
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fn position(&self, face: usize, vert: usize) -> [f32; 3];
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/// Returns the normal of a vertex.
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fn normal(&self, face: usize, vert: usize) -> [f32; 3];
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/// Returns the texture coordinate of a vertex.
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fn tex_coord(&self, face: usize, vert: usize) -> [f32; 2];
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/// Sets the generated tangent for a vertex.
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/// Leave this function unimplemented if you are implementing
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/// `set_tangent_encoded`.
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fn set_tangent(
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&mut self,
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tangent: [f32; 3],
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_bi_tangent: [f32; 3],
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_f_mag_s: f32,
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_f_mag_t: f32,
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bi_tangent_preserves_orientation: bool,
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face: usize,
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vert: usize,
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) {
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let sign = if bi_tangent_preserves_orientation {
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1.0
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} else {
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-1.0
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};
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self.set_tangent_encoded([tangent[0], tangent[1], tangent[2], sign], face, vert);
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}
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/// Sets the generated tangent for a vertex with its bi-tangent encoded as the 'W' (4th)
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/// component in the tangent. The 'W' component marks if the bi-tangent is flipped. This
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/// is called by the default implementation of `set_tangent`; therefore, this function will
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/// not be called by the crate unless `set_tangent` is unimplemented.
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fn set_tangent_encoded(&mut self, _tangent: [f32; 4], _face: usize, _vert: usize) {}
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}
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/// Generates tangents for the input geometry.
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///
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/// # Errors
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///
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/// Returns `false` if the geometry is unsuitable for tangent generation including,
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/// but not limited to, lack of vertices.
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#[allow(unsafe_code)]
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pub fn generate_tangents<I: Geometry>(geometry: &mut I) -> bool {
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unsafe { generated::genTangSpace(geometry, 180.0) }
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}
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fn get_position<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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geometry.position(face, vert).into()
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}
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fn get_tex_coord<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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let tex_coord: Vec2 = geometry.tex_coord(face, vert).into();
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let val = tex_coord.extend(1.0);
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val
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}
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fn get_normal<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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geometry.normal(face, vert).into()
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}
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fn index_to_face_vert(index: usize) -> (usize, usize) {
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(index >> 2, index & 0x3)
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}
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fn face_vert_to_index(face: usize, vert: usize) -> usize {
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face << 2 | vert & 0x3
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}
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