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style: Remove some magic from the bindings

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This simplifies a tiny bit our bindings in some places, and complicates
it in others, but over all I think it's better.

It requires a bit more manual code in the rust side to drop and cast the
relevant pointers (which was done implicitly before), but it's a lot
less magic than it used to be, and that's all autogenerated so consumers
don't need to care about it.

The set up is still not ideal. I don't like that we rely on destructors
running in both sides of the FFI boundary, but that's for another day.

This is the last usage of RawOffsetArc, so remove that. We now support
proper Arc<> in structs (GridTemplateAreas uses it), so I don't think
we'll need it any time soon.

Differential Revision: https://phabricator.services.mozilla.com/D177905
This commit is contained in:
Emilio Cobos Álvarez 2023-05-12 23:33:12 +00:00 • committed by Martin Robinson
parent e9bf977369
commit d1046739fc
7 changed files with 320 additions and 472 deletions
Download patch file Download diff file Expand all files Collapse all files

168
components/servo_arc/lib.rs
View file

@ -218,8 +218,6 @@ impl<T> Arc<T> {
/// Convert the Arc<T> to a raw pointer, suitable for use across FFI
///
/// Note: This returns a pointer to the data T, which is offset in the allocation.
///
/// It is recommended to use RawOffsetArc for this.
#[inline]
pub fn into_raw(this: Self) -> *const T {
let ptr = unsafe { &((*this.ptr()).data) as *const _ };
@ -286,26 +284,6 @@ impl<T> Arc<T> {
ArcBorrow(&**self)
}
/// Temporarily converts |self| into a bonafide RawOffsetArc and exposes it to the
/// provided callback. The refcount is not modified.
#[inline(always)]
pub fn with_raw_offset_arc<F, U>(&self, f: F) -> U
where
F: FnOnce(&RawOffsetArc<T>) -> U,
{
// Synthesize transient Arc, which never touches the refcount of the ArcInner.
let transient = unsafe { NoDrop::new(Arc::into_raw_offset(ptr::read(self))) };
// Expose the transient Arc to the callback, which may clone it if it wants.
let result = f(&transient);
// Forget the transient Arc to leave the refcount untouched.
mem::forget(transient);
// Forward the result.
result
}
/// Returns the address on the heap of the Arc itself -- not the T within it -- for memory
/// reporting.
///
@ -1100,149 +1078,6 @@ impl<H: PartialEq, T: PartialEq> PartialEq for ThinArc<H, T> {
impl<H: Eq, T: Eq> Eq for ThinArc<H, T> {}
/// An `Arc`, except it holds a pointer to the T instead of to the
/// entire ArcInner. This struct is FFI-compatible.
///
/// ```text
/// Arc<T> RawOffsetArc<T>
/// | |
/// v v
/// ---------------------
/// | RefCount | T (data) | [ArcInner<T>]
/// ---------------------
/// ```
///
/// This means that this is a direct pointer to
/// its contained data (and can be read from by both C++ and Rust),
/// but we can also convert it to a "regular" Arc<T> by removing the offset.
///
/// This is very useful if you have an Arc-containing struct shared between Rust and C++,
/// and wish for C++ to be able to read the data behind the `Arc` without incurring
/// an FFI call overhead.
#[derive(Eq)]
#[repr(C)]
pub struct RawOffsetArc<T> {
ptr: ptr::NonNull<T>,
}
unsafe impl<T: Sync + Send> Send for RawOffsetArc<T> {}
unsafe impl<T: Sync + Send> Sync for RawOffsetArc<T> {}
impl<T> Deref for RawOffsetArc<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
unsafe { &*self.ptr.as_ptr() }
}
}
impl<T> Clone for RawOffsetArc<T> {
#[inline]
fn clone(&self) -> Self {
Arc::into_raw_offset(self.clone_arc())
}
}
impl<T> Drop for RawOffsetArc<T> {
fn drop(&mut self) {
let _ = Arc::from_raw_offset(RawOffsetArc { ptr: self.ptr });
}
}
impl<T: fmt::Debug> fmt::Debug for RawOffsetArc<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}
impl<T: PartialEq> PartialEq for RawOffsetArc<T> {
fn eq(&self, other: &RawOffsetArc<T>) -> bool {
*(*self) == *(*other)
}
}
impl<T> RawOffsetArc<T> {
/// Temporarily converts |self| into a bonafide Arc and exposes it to the
/// provided callback. The refcount is not modified.
#[inline]
pub fn with_arc<F, U>(&self, f: F) -> U
where
F: FnOnce(&Arc<T>) -> U,
{
// Synthesize transient Arc, which never touches the refcount of the ArcInner.
let transient = unsafe { NoDrop::new(Arc::from_raw(self.ptr.as_ptr())) };
// Expose the transient Arc to the callback, which may clone it if it wants.
let result = f(&transient);
// Forget the transient Arc to leave the refcount untouched.
// XXXManishearth this can be removed when unions stabilize,
// since then NoDrop becomes zero overhead
mem::forget(transient);
// Forward the result.
result
}
/// If uniquely owned, provide a mutable reference
/// Else create a copy, and mutate that
///
/// This is functionally the same thing as `Arc::make_mut`
#[inline]
pub fn make_mut(&mut self) -> &mut T
where
T: Clone,
{
unsafe {
// extract the RawOffsetArc as an owned variable
let this = ptr::read(self);
// treat it as a real Arc
let mut arc = Arc::from_raw_offset(this);
// obtain the mutable reference. Cast away the lifetime
// This may mutate `arc`
let ret = Arc::make_mut(&mut arc) as *mut _;
// Store the possibly-mutated arc back inside, after converting
// it to a RawOffsetArc again
ptr::write(self, Arc::into_raw_offset(arc));
&mut *ret
}
}
/// Clone it as an `Arc`
#[inline]
pub fn clone_arc(&self) -> Arc<T> {
RawOffsetArc::with_arc(self, |a| a.clone())
}
/// Produce a pointer to the data that can be converted back
/// to an `Arc`
#[inline]
pub fn borrow_arc<'a>(&'a self) -> ArcBorrow<'a, T> {
ArcBorrow(&**self)
}
}
impl<T> Arc<T> {
/// Converts an `Arc` into a `RawOffsetArc`. This consumes the `Arc`, so the refcount
/// is not modified.
#[inline]
pub fn into_raw_offset(a: Self) -> RawOffsetArc<T> {
unsafe {
RawOffsetArc {
ptr: ptr::NonNull::new_unchecked(Arc::into_raw(a) as *mut T),
}
}
}
/// Converts a `RawOffsetArc` into an `Arc`. This consumes the `RawOffsetArc`, so the refcount
/// is not modified.
#[inline]
pub fn from_raw_offset(a: RawOffsetArc<T>) -> Self {
let ptr = a.ptr.as_ptr();
mem::forget(a);
unsafe { Arc::from_raw(ptr) }
}
}
/// A "borrowed `Arc`". This is a pointer to
/// a T that is known to have been allocated within an
/// `Arc`.
@ -1253,8 +1088,7 @@ impl<T> Arc<T> {
/// It's also a direct pointer to `T`, so using this involves less pointer-chasing
///
/// However, C++ code may hand us refcounted things as pointers to T directly,
/// so we have to conjure up a temporary `Arc` on the stack each time. The
/// same happens for when the object is managed by a `RawOffsetArc`.
/// so we have to conjure up a temporary `Arc` on the stack each time.
///
/// `ArcBorrow` lets us deal with borrows of known-refcounted objects
/// without needing to worry about where the `Arc<T>` is.

4
components/style/gecko/media_queries.rs
View file

@ -131,7 +131,7 @@ impl Device {
line_height,
pres_context.map_or(std::ptr::null(), |pc| pc),
vertical,
font.gecko(),
&**font,
element.map_or(std::ptr::null(), |e| e.0)
)
});
@ -231,7 +231,7 @@ impl Device {
bindings::Gecko_GetFontMetrics(
pc,
vertical,
font.gecko(),
&**font,
base_size,
// we don't use the user font set in a media query
!in_media_query,

23
components/style/properties/cascade.rs
View file

@ -900,7 +900,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
let builder = &mut self.context.builder;
let default_font_type = {
let font = builder.get_font().gecko();
let font = builder.get_font();
if !font.mFont.family.is_initial {
return;
@ -922,9 +922,8 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
default_font_type
};
let font = builder.mutate_font().gecko_mut();
// NOTE: Leaves is_initial untouched.
font.mFont.family.families = FontFamily::generic(default_font_type).families.clone();
builder.mutate_font().mFont.family.families = FontFamily::generic(default_font_type).families.clone();
}
/// Prioritize user fonts if needed by pref.
@ -943,7 +942,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
let builder = &mut self.context.builder;
let default_font_type = {
let font = builder.get_font().gecko();
let font = builder.get_font();
if font.mFont.family.is_system_font {
return;
@ -961,7 +960,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
}
};
let font = builder.mutate_font().gecko_mut();
let font = builder.mutate_font();
font.mFont.family.families.prioritize_first_generic_or_prepend(default_font_type);
}
@ -986,7 +985,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
},
};
if font.gecko().mScriptUnconstrainedSize == new_size.computed_size {
if font.mScriptUnconstrainedSize == new_size.computed_size {
return;
}
@ -1013,9 +1012,9 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
let builder = &mut self.context.builder;
let min_font_size = {
let font = builder.get_font().gecko();
let font = builder.get_font();
let min_font_size = unsafe {
bindings::Gecko_nsStyleFont_ComputeMinSize(font, builder.device.document())
bindings::Gecko_nsStyleFont_ComputeMinSize(&**font, builder.device.document())
};
if font.mFont.size.0 >= min_font_size {
@ -1025,7 +1024,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
NonNegative(min_font_size)
};
builder.mutate_font().gecko_mut().mFont.size = min_font_size;
builder.mutate_font().mFont.size = min_font_size;
}
/// <svg:text> is not affected by text zoom, and it uses a preshint to disable it. We fix up
@ -1133,8 +1132,8 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
let (new_size, new_unconstrained_size) = {
let builder = &self.context.builder;
let font = builder.get_font().gecko();
let parent_font = builder.get_parent_font().gecko();
let font = builder.get_font();
let parent_font = builder.get_parent_font();
let delta = font.mMathDepth.saturating_sub(parent_font.mMathDepth);
@ -1195,7 +1194,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
)
}
};
let font = self.context.builder.mutate_font().gecko_mut();
let font = self.context.builder.mutate_font();
font.mFont.size = NonNegative(new_size);
font.mSize = NonNegative(new_size);
font.mScriptUnconstrainedSize = NonNegative(new_unconstrained_size);

532
components/style/properties/gecko.mako.rs
View file

File diff suppressed because it is too large Load diff

2
components/style/properties/longhands/font.mako.rs
View file

@ -401,7 +401,7 @@ pub mod system_font {
bindings::Gecko_nsFont_InitSystem(
system.as_mut_ptr(),
*self,
cx.style().get_font().gecko(),
&**cx.style().get_font(),
cx.device().document()
);
&mut *system.as_mut_ptr()

57
components/style/properties/properties.mako.rs
View file

@ -3098,14 +3098,9 @@ impl ComputedValues {
self.rules.as_ref().unwrap()
}
/// Returns the visited style, if any.
pub fn visited_style(&self) -> Option<<&ComputedValues> {
self.visited_style.as_deref()
}
/// Returns the visited rules, if applicable.
pub fn visited_rules(&self) -> Option<<&StrongRuleNode> {
self.visited_style.as_ref().and_then(|s| s.rules.as_ref())
self.visited_style().and_then(|s| s.rules.as_ref())
}
/// Gets a reference to the custom properties map (if one exists).
@ -3346,6 +3341,11 @@ impl ops::DerefMut for ComputedValues {
#[cfg(feature = "servo")]
impl ComputedValuesInner {
/// Returns the visited style, if any.
pub fn visited_style(&self) -> Option<<&ComputedValues> {
self.visited_style.as_deref()
}
% for style_struct in data.active_style_structs():
/// Clone the ${style_struct.name} struct.
#[inline]
@ -3359,12 +3359,6 @@ impl ComputedValuesInner {
&self.${style_struct.ident}
}
/// Gets an immutable reference to the refcounted value that wraps
/// `${style_struct.name}`.
pub fn ${style_struct.name_lower}_arc(&self) -> &Arc<style_structs::${style_struct.name}> {
&self.${style_struct.ident}
}
/// Get a mutable reference to the ${style_struct.name} struct.
#[inline]
pub fn mutate_${style_struct.name_lower}(&mut self) -> &mut style_structs::${style_struct.name} {
@ -3563,24 +3557,10 @@ impl ComputedValuesInner {
}
}
% if engine == "gecko":
pub use crate::servo_arc::RawOffsetArc as BuilderArc;
/// Clone an arc, returning a regular arc
fn clone_arc<T: 'static>(x: &BuilderArc<T>) -> Arc<T> {
Arc::from_raw_offset(x.clone())
}
% else:
pub use crate::servo_arc::Arc as BuilderArc;
/// Clone an arc, returning a regular arc
fn clone_arc<T: 'static>(x: &BuilderArc<T>) -> Arc<T> {
x.clone()
}
% endif
/// A reference to a style struct of the parent, or our own style struct.
pub enum StyleStructRef<'a, T: 'static> {
/// A borrowed struct from the parent, for example, for inheriting style.
Borrowed(&'a BuilderArc<T>),
Borrowed(&'a T),
/// An owned struct, that we've already mutated.
Owned(UniqueArc<T>),
/// Temporarily vacated, will panic if accessed
@ -3595,7 +3575,7 @@ where
/// borrowed value, or returning the owned one.
pub fn mutate(&mut self) -> &mut T {
if let StyleStructRef::Borrowed(v) = *self {
*self = StyleStructRef::Owned(UniqueArc::new((**v).clone()));
*self = StyleStructRef::Owned(UniqueArc::new(v.clone()));
}
match *self {
@ -3614,8 +3594,8 @@ where
pub fn ptr_eq(&self, struct_to_copy_from: &T) -> bool {
match *self {
StyleStructRef::Owned(..) => false,
StyleStructRef::Borrowed(arc) => {
&**arc as *const T == struct_to_copy_from as *const T
StyleStructRef::Borrowed(s) => {
s as *const T == struct_to_copy_from as *const T
}
StyleStructRef::Vacated => panic!("Accessed vacated style struct")
}
@ -3632,7 +3612,7 @@ where
match inner {
StyleStructRef::Owned(arc) => arc,
StyleStructRef::Borrowed(arc) => UniqueArc::new((**arc).clone()),
StyleStructRef::Borrowed(s) => UniqueArc::new(s.clone()),
StyleStructRef::Vacated => panic!("Accessed vacated style struct"),
}
}
@ -3658,7 +3638,8 @@ where
pub fn build(self) -> Arc<T> {
match self {
StyleStructRef::Owned(v) => v.shareable(),
StyleStructRef::Borrowed(v) => clone_arc(v),
// SAFETY: We know all style structs are arc-allocated.
StyleStructRef::Borrowed(v) => unsafe { Arc::from_raw_addrefed(v) },
StyleStructRef::Vacated => panic!("Accessed vacated style struct")
}
}
@ -3670,7 +3651,7 @@ impl<'a, T: 'a> ops::Deref for StyleStructRef<'a, T> {
fn deref(&self) -> &T {
match *self {
StyleStructRef::Owned(ref v) => &**v,
StyleStructRef::Borrowed(v) => &**v,
StyleStructRef::Borrowed(v) => v,
StyleStructRef::Vacated => panic!("Accessed vacated style struct")
}
}
@ -3773,9 +3754,9 @@ impl<'a> StyleBuilder<'a> {
visited_style: None,
% for style_struct in data.active_style_structs():
% if style_struct.inherited:
${style_struct.ident}: StyleStructRef::Borrowed(inherited_style.${style_struct.name_lower}_arc()),
${style_struct.ident}: StyleStructRef::Borrowed(inherited_style.get_${style_struct.name_lower}()),
% else:
${style_struct.ident}: StyleStructRef::Borrowed(reset_style.${style_struct.name_lower}_arc()),
${style_struct.ident}: StyleStructRef::Borrowed(reset_style.get_${style_struct.name_lower}()),
% endif
% endfor
}
@ -3813,7 +3794,7 @@ impl<'a> StyleBuilder<'a> {
visited_style: None,
% for style_struct in data.active_style_structs():
${style_struct.ident}: StyleStructRef::Borrowed(
style_to_derive_from.${style_struct.name_lower}_arc()
style_to_derive_from.get_${style_struct.name_lower}()
),
% endfor
}
@ -3824,7 +3805,7 @@ impl<'a> StyleBuilder<'a> {
% for style_struct in data.active_style_structs():
% if not style_struct.inherited:
self.${style_struct.ident} =
StyleStructRef::Borrowed(style.${style_struct.name_lower}_arc());
StyleStructRef::Borrowed(style.get_${style_struct.name_lower}());
% endif
% endfor
}
@ -3991,7 +3972,7 @@ impl<'a> StyleBuilder<'a> {
/// Reset the current `${style_struct.name}` style to its default value.
pub fn reset_${style_struct.name_lower}_struct(&mut self) {
self.${style_struct.ident} =
StyleStructRef::Borrowed(self.reset_style.${style_struct.name_lower}_arc());
StyleStructRef::Borrowed(self.reset_style.get_${style_struct.name_lower}());
}
% endfor
<% del style_struct %>

6
components/style/values/specified/font.rs
View file

@ -775,13 +775,13 @@ impl FontSizeKeyword {
#[cfg(feature = "gecko")]
#[inline]
fn to_length(&self, cx: &Context) -> NonNegativeLength {
let gecko_font = cx.style().get_font().gecko();
let family = &gecko_font.mFont.family.families;
let font = cx.style().get_font();
let family = &font.mFont.family.families;
let generic = family
.single_generic()
.unwrap_or(computed::GenericFontFamily::None);
let base_size = unsafe {
Atom::with(gecko_font.mLanguage.mRawPtr, |language| {
Atom::with(font.mLanguage.mRawPtr, |language| {
cx.device().base_size_for_generic(language, generic)
})
};