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Make LOCAL_CONTEXT_KEY safe and non-leaky.

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`LOCAL_CONTEXT_KEY` is currently a `Cell<*mut LocalLayoutContext>`. The use
of the raw pointer means that the `LocalLayoutContext` is not dropped when
the thread dies; this leaks FreeType instances and probably other
things. There are also some unsafe getter functions in `LayoutContext`
(`font_context`, `applicable_declarations_cache` and
`style_sharing_candidate_cache`) that @eddyb says involve undefined
behaviour.

This changeset changes `LOCAL_CONTEXT_KEY` to
`RefCell<Option<Rc<LocalLayoutContext>>>`. This fixes the leak and also
results in safe getters.

(Fixes #6282.)
This commit is contained in:
Nicholas Nethercote 2015-06-04 20:08:19 -07:00
parent 2ca606aaba
commit 9b4d39d6d1
7 changed files with 38 additions and 48 deletions
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6
components/layout/construct.rs
View file

@ -423,7 +423,7 @@ impl<'a> FlowConstructor<'a> {
// for runs might collapse so much whitespace away that only hypothetical fragments
// remain. In that case the inline flow will compute its ascent and descent to be zero.
let scanned_fragments =
TextRunScanner::new().scan_for_runs(self.layout_context.font_context(),
TextRunScanner::new().scan_for_runs(&mut self.layout_context.font_context(),
fragments.fragments);
let mut inline_flow_ref =
FlowRef::new(box InlineFlow::from_fragments(scanned_fragments,
@ -446,7 +446,7 @@ impl<'a> FlowConstructor<'a> {
let (ascent, descent) =
inline_flow.compute_minimum_ascent_and_descent(self.layout_context.font_context(),
inline_flow.compute_minimum_ascent_and_descent(&mut self.layout_context.font_context(),
&**node.style());
inline_flow.minimum_block_size_above_baseline = ascent;
inline_flow.minimum_depth_below_baseline = descent;
@ -1140,7 +1140,7 @@ impl<'a> FlowConstructor<'a> {
SpecificFragmentInfo::UnscannedText(
UnscannedTextFragmentInfo::from_text(text))));
let marker_fragments = TextRunScanner::new().scan_for_runs(
self.layout_context.font_context(),
&mut self.layout_context.font_context(),
unscanned_marker_fragments);
debug_assert!(marker_fragments.len() == 1);
marker_fragments.fragments.into_iter().next()