glib: Add new marker traits for transparent types

Author: sdroege

glib/src/boxed.rs

@@ -59,6 +59,9 @@ macro_rules! glib_boxed_wrapper {
             type GlibType = *mut $ffi_name;
         }
 
+        #[doc(hidden)]
+        unsafe impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::translate::TransparentPtrType for $name $(<$($generic),+>)? {}
+
         #[doc(hidden)]
         impl<'a $(, $($generic $(: $bound $(+ $bound2)*)?),+)?> $crate::translate::ToGlibPtr<'a, *const $ffi_name> for $name $(<$($generic),+>)? {
             type Storage = std::marker::PhantomData<&'a $crate::boxed::Boxed<$ffi_name, Self>>;

glib/src/boxed_inline.rs

@@ -164,6 +164,11 @@ macro_rules! glib_boxed_inline_wrapper {
             type GlibType = *mut $ffi_name;
         }
 
+        #[doc(hidden)]
+        unsafe impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::translate::TransparentType for $name $(<$($generic),+>)? {
+            type GlibType = $ffi_name;
+        }
+
         #[doc(hidden)]
         impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::translate::Uninitialized for $name $(<$($generic),+>)? {
             #[inline]

glib/src/object.rs

@@ -903,6 +903,9 @@ macro_rules! glib_object_wrapper {
             type GlibType = *mut $ffi_name;
         }
 
+        #[doc(hidden)]
+        unsafe impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::translate::TransparentPtrType for $name $(<$($generic),+>)? {}
+
         #[doc(hidden)]
         unsafe impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::object::ObjectType for $name $(<$($generic),+>)? {
             type GlibType = $ffi_name;

glib/src/shared.rs

@@ -71,6 +71,9 @@ macro_rules! glib_shared_wrapper {
             type GlibType = *mut $ffi_name;
         }
 
+        #[doc(hidden)]
+        unsafe impl $(<$($generic $(: $bound $(+ $bound2)*)?),+>)? $crate::translate::TransparentPtrType for $name $(<$($generic),+>)? {}
+
         #[doc(hidden)]
         impl<'a $(, $($generic $(: $bound $(+ $bound2)*)?),+)?> $crate::translate::ToGlibPtr<'a, *mut $ffi_name> for $name $(<$($generic),+>)? {
             type Storage = std::marker::PhantomData<&'a $crate::shared::Shared<$ffi_name, Self>>;

glib/src/translate.rs

@@ -352,6 +352,10 @@ impl IntoGlib for char {
     }
 }
 
+unsafe impl TransparentType for char {
+    type GlibType = u32;
+}
+
 impl IntoGlib for Option<char> {
     type GlibType = u32;
 
@@ -1998,6 +2002,10 @@ impl FromGlibContainerAsVec<bool, *mut ffi::gboolean> for bool {
 
 macro_rules! impl_from_glib_container_as_vec_fundamental {
     ($name:ty) => {
+        unsafe impl TransparentType for $name {
+            type GlibType = $name;
+        }
+
         impl FromGlibContainerAsVec<$name, *const $name> for $name {
             unsafe fn from_glib_none_num_as_vec(ptr: *const $name, num: usize) -> Vec<Self> {
                 if num == 0 || ptr.is_null() {
@@ -2605,6 +2613,24 @@ where
     }
 }
 
+/// Trait for types that have the same memory representation as a pointer to their FFI type.
+///
+/// Values of types implementing this trait can be transmuted to pointers of the FFI type,
+/// references to pointers of pointers to the FFI type.
+pub unsafe trait TransparentPtrType: Clone + Sized + GlibPtrDefault {}
+
+/// Trait for types that have the same memory representation as their FFI type.
+///
+/// Values of types implementing this trait can be transmuted directly to the FFI type, references
+/// to pointers to the FFI type.
+pub unsafe trait TransparentType: Clone + Sized {
+    type GlibType;
+}
+
+unsafe impl<T: TransparentPtrType> TransparentType for T {
+    type GlibType = <T as GlibPtrDefault>::GlibType;
+}
+
 #[cfg(test)]
 mod tests {
     use std::{collections::HashMap, fs};

glib/src/types.rs

@@ -14,6 +14,10 @@ use crate::{translate::*, Slice};
 #[repr(transparent)]
 pub struct Type(ffi::GType);
 
+unsafe impl TransparentType for Type {
+    type GlibType = ffi::GType;
+}
+
 impl Type {
     // rustdoc-stripper-ignore-next
     /// An invalid `Type` used as error return value in some functions