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fix(macos): keep chat text layout contiguous to prevent streaming gap/overlap #26317

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Merged
siddseethepalli merged 1 commit into from
Apr 18, 2026
Merged

fix(macos): keep chat text layout contiguous to prevent streaming gap/overlap #26317

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18 changes: 13 additions & 5 deletions clients/shared/DesignSystem/Components/Display/SelectableTextView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -177,11 +177,19 @@ public struct VSelectableTextView: NSViewRepresentable {
// Reference: https://developer.apple.com/documentation/appkit/nstextview/1449309-layoutmanager
let textStorage = NSTextStorage()
let layoutManager = NSLayoutManager()
// Confine glyph generation to the requested bounding rect so that
// attaching the text view to its hosting view does not force full
// document layout on the main thread.
// https://developer.apple.com/documentation/appkit/nslayoutmanager/allowsnoncontiguouslayout
layoutManager.allowsNonContiguousLayout = true
// Contiguous (default) layout: the measurement path uses
// `NSLayoutManager.ensureLayout(for:)` + `usedRect(for:)` on a separate
// TextKit stack that always lays out every glyph, so the frame we
// hand SwiftUI via `.frame(height:)` assumes the NSTextView will
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// render every glyph in that same rect. Non-contiguous layout leaves
// glyphs pending until the view scrolls or draws them, which races
// with streaming updates — the NSTextView briefly paints a smaller
// laid-out region inside the (correctly-measured) larger frame,
// producing a visible gap; the next sibling then gets placed via
// the measured frame and the lazy glyphs later paint outside it,
// producing overlap. Keep this contiguous for correctness here.
// VCodeView / HighlightedTextView still opt in to non-contiguous
// layout independently for their own scroll-attachment perf fix.
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textStorage.addLayoutManager(layoutManager)
let textContainer = NSTextContainer(size: NSSize(
width: 0,
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