[Text] Fixes double reorder of cached bidi runs - #21351
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MrJul
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* Fix double reorder with cached runs * Revert change * Add covering unit tests * Remove worktrees * Update API baseline
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What does the pull request do?
Fix double reorder with cached bidi runs
When
TextRunCachewas enabled and a paragraph contained RTL text, recreating aTextLayoutfrom the same cache would render RTL runs incorrectly.The root cause was in how shaped runs were shared between the cache and the formatter:
The cache stored a
ShapedTextRunreferencing aShapedBufferbacked by a rentedGlyphInfo[]array.The formatter created "non-owning" copies for use in the line by passing the same
ArraySlice<GlyphInfo>to a newShapedBufferconstructor; both the cached run and the line's run therefore pointed at the same backing array.BidiReorderer.Reverse()mutated glyph order in-place on the line's copy, which also reversed the cached run's glyphs.On the next layout from cache, the retrieved run had IsReversed = false (fresh copy) but an already-reversed buffer.
BidiReordererreversed it a second time, putting RTL glyphs back into logical (ascending-cluster) order — causing wrong visual rendering.What is the current behavior?
What is the updated/expected behavior with this PR?
How was the solution implemented (if it's not obvious)?
ShapedTextRunis now ref-counted (AddRef/Dispose). The shaper produces one reference; callingAddRef()yields an additional owned reference rather than a shallow buffer copy.BidiReordererno longer calls Reverse() on individual runs. RTLShapedBuffers are produced by the shaper already in visual (descending-cluster) order; the reorderer only shuffles the run sequence.TextFormatterImpl: when adding runs to the cache,AddRefis called so both the cache and the current line hold independent, correctly-counted references. When reading from cache (FormatLineFromCache), each run's ref-count is incremented rather than copying the buffer.TextRunCache: properly disposes the old entry (releasing its reference) when a key is overwritten, preventing leaks.Checklist
Breaking changes
Obsoletions / Deprecations
Fixed issues