dear_imgui_rs/

internal.rs

//! Internal low-level types
//!
//! Exposes helpers mirroring Dear ImGui internals (e.g. `ImVector`, data type
//! markers). These are primarily for advanced integrations; APIs may change.
//!
#![allow(
    clippy::cast_possible_truncation,
    clippy::cast_sign_loss,
    clippy::as_conversions
)]
use crate::sys;
use std::ffi::c_int;
use std::slice;

/// A primary data type
#[repr(i32)]
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum DataType {
    I8 = sys::ImGuiDataType_S8 as i32,
    U8 = sys::ImGuiDataType_U8 as i32,
    I16 = sys::ImGuiDataType_S16 as i32,
    U16 = sys::ImGuiDataType_U16 as i32,
    I32 = sys::ImGuiDataType_S32 as i32,
    U32 = sys::ImGuiDataType_U32 as i32,
    I64 = sys::ImGuiDataType_S64 as i32,
    U64 = sys::ImGuiDataType_U64 as i32,
    F32 = sys::ImGuiDataType_Float as i32,
    F64 = sys::ImGuiDataType_Double as i32,
}

/// Primitive type marker.
///
/// If this trait is implemented for a type, it is assumed to have *exactly* the same
/// representation in memory as the primitive value described by the associated `KIND` constant.
///
/// # Safety
/// The `DataType` *must* have the same representation as the primitive value of `KIND`.
pub unsafe trait DataTypeKind: Copy {
    const KIND: DataType;
}

unsafe impl DataTypeKind for i8 {
    const KIND: DataType = DataType::I8;
}
unsafe impl DataTypeKind for u8 {
    const KIND: DataType = DataType::U8;
}
unsafe impl DataTypeKind for i16 {
    const KIND: DataType = DataType::I16;
}
unsafe impl DataTypeKind for u16 {
    const KIND: DataType = DataType::U16;
}
unsafe impl DataTypeKind for i32 {
    const KIND: DataType = DataType::I32;
}
unsafe impl DataTypeKind for u32 {
    const KIND: DataType = DataType::U32;
}
unsafe impl DataTypeKind for i64 {
    const KIND: DataType = DataType::I64;
}
unsafe impl DataTypeKind for u64 {
    const KIND: DataType = DataType::U64;
}
unsafe impl DataTypeKind for f32 {
    const KIND: DataType = DataType::F32;
}
unsafe impl DataTypeKind for f64 {
    const KIND: DataType = DataType::F64;
}

unsafe impl DataTypeKind for usize {
    #[cfg(target_pointer_width = "16")]
    const KIND: DataType = DataType::U16;

    #[cfg(target_pointer_width = "32")]
    const KIND: DataType = DataType::U32;

    #[cfg(target_pointer_width = "64")]
    const KIND: DataType = DataType::U64;

    // Fallback for when we are on a weird system width
    //
    #[cfg(not(any(
        target_pointer_width = "16",
        target_pointer_width = "32",
        target_pointer_width = "64"
    )))]
    compile_error!(
        "cannot impl DataTypeKind for usize: unsupported target pointer width. supported values are 16, 32, 64"
    );
}

unsafe impl DataTypeKind for isize {
    #[cfg(target_pointer_width = "16")]
    const KIND: DataType = DataType::I16;

    #[cfg(target_pointer_width = "32")]
    const KIND: DataType = DataType::I32;

    #[cfg(target_pointer_width = "64")]
    const KIND: DataType = DataType::I64;

    // Fallback for when we are on a weird system width
    //
    #[cfg(not(any(
        target_pointer_width = "16",
        target_pointer_width = "32",
        target_pointer_width = "64"
    )))]
    compile_error!(
        "cannot impl DataTypeKind for isize: unsupported target pointer width. supported values are 16, 32, 64"
    );
}

/// A generic version of the raw imgui-sys ImVector struct types
///
/// This provides a safe Rust interface to Dear ImGui's vector type.
#[repr(C)]
pub struct ImVector<T> {
    pub(crate) size: c_int,
    pub(crate) capacity: c_int,
    pub(crate) data: *mut T,
}

impl<T> ImVector<T> {
    /// Returns the vector as a slice
    #[inline]
    pub fn as_slice(&self) -> &[T] {
        if self.size == 0 || self.data.is_null() {
            &[]
        } else {
            unsafe { slice::from_raw_parts(self.data, self.size as usize) }
        }
    }

    /// Returns the vector as a mutable slice
    #[inline]
    pub fn as_slice_mut(&mut self) -> &mut [T] {
        if self.size == 0 || self.data.is_null() {
            &mut []
        } else {
            unsafe { slice::from_raw_parts_mut(self.data, self.size as usize) }
        }
    }

    /// Returns the number of elements in the vector
    #[inline]
    pub fn len(&self) -> usize {
        self.size as usize
    }

    /// Returns true if the vector is empty
    #[inline]
    pub fn is_empty(&self) -> bool {
        self.size == 0
    }
}

impl<T> Default for ImVector<T> {
    fn default() -> Self {
        Self {
            size: 0,
            capacity: 0,
            data: std::ptr::null_mut(),
        }
    }
}

impl<T> ImVector<T> {
    /// Returns an iterator over the elements
    #[inline]
    pub fn iter(&self) -> slice::Iter<'_, T> {
        self.as_slice().iter()
    }

    /// Returns a mutable iterator over the elements
    #[inline]
    pub fn iter_mut(&mut self) -> slice::IterMut<'_, T> {
        self.as_slice_mut().iter_mut()
    }
}

/// Cast a bindgen-generated `ImVector_*` to our generic `ImVector<T>` view.
///
/// Safety: `raw` must be a pointer/reference to a C `ImVector` instantiated
/// with the same element type `T` (layout-compatible). Only use with
/// bindgen-generated `ImVector_*` structs from dear-imgui-sys.
#[inline]
pub unsafe fn imvector_cast_ref<T, R>(raw: &R) -> &ImVector<T> {
    unsafe { &*(raw as *const R as *const ImVector<T>) }
}

/// Mutable variant of [`imvector_cast_ref`]. See its safety contract.
#[inline]
pub unsafe fn imvector_cast_mut<T, R>(raw: &mut R) -> &mut ImVector<T> {
    unsafe { &mut *(raw as *mut R as *mut ImVector<T>) }
}

/// Marks a type as a transparent wrapper over a raw type
pub trait RawWrapper {
    /// Wrapped raw type
    type Raw;
    /// Returns an immutable reference to the wrapped raw value
    ///
    /// # Safety
    ///
    /// It is up to the caller to use the returned raw reference without causing undefined
    /// behaviour or breaking safety rules.
    unsafe fn raw(&self) -> &Self::Raw;
    /// Returns a mutable reference to the wrapped raw value
    ///
    /// # Safety
    ///
    /// It is up to the caller to use the returned mutable raw reference without causing undefined
    /// behaviour or breaking safety rules.
    unsafe fn raw_mut(&mut self) -> &mut Self::Raw;
}

/// Casting from/to a raw type that has the same layout and alignment as the target type
///
/// # Safety
///
/// Each function outlines its own safety contract, which generally is
/// that the cast from `T` to `Self` is valid.
pub unsafe trait RawCast<T>: Sized {
    /// Casts an immutable reference from the raw type
    ///
    /// # Safety
    ///
    /// It is up to the caller to guarantee the cast is valid.
    #[inline]
    unsafe fn from_raw(raw: &T) -> &Self {
        unsafe { &*(raw as *const _ as *const Self) }
    }

    /// Casts a mutable reference from the raw type
    ///
    /// # Safety
    ///
    /// It is up to the caller to guarantee the cast is valid.
    #[inline]
    unsafe fn from_raw_mut(raw: &mut T) -> &mut Self {
        unsafe { &mut *(raw as *mut _ as *mut Self) }
    }

    /// Casts an immutable reference to the raw type
    ///
    /// # Safety
    ///
    /// It is up to the caller to guarantee the cast is valid.
    #[inline]
    unsafe fn raw(&self) -> &T {
        unsafe { &*(self as *const _ as *const T) }
    }

    /// Casts a mutable reference to the raw type
    ///
    /// # Safety
    ///
    /// It is up to the caller to guarantee the cast is valid.
    #[inline]
    unsafe fn raw_mut(&mut self) -> &mut T {
        unsafe { &mut *(self as *mut _ as *mut T) }
    }
}