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InstantPage V2: fix inline emoji/image/formula x-offset on RTL lines

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Inline attachments anchored their left edge at
CTLineGetOffsetForStringIndex(line, range.location), which is the glyph's
LEFT edge for LTR runs but its RIGHT edge for RTL runs (string index
increases leftward). On an RTL line (e.g. an Arabic thinking block) this
shoved emoji/images/formulas ~one advance (~24pt) too far right while the
CoreText-drawn text stayed correct.

Add v2LeadingOffsetForRange(_:range:), which returns
min(offset(start), offset(end)) with directional-boundary secondary-offset
handling — the true leading edge in both directions. Mirrors
Display.TextNode.addEmbeddedItem and the strikethrough/underline/spoiler
decorations already in this file (which used the min/abs form; the inline
attachments had regressed to a single offset). Applied at all 5 sites:
the emoji/image/formula display frames and the emoji/image characterRect
(reveal mask). Widths unchanged; only x corrected. LTR is byte-identical.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
isaac 2026-06-04 20:39:13 +02:00
parent 52db80698c
commit 0a92dbddc3
2 changed files with 33 additions and 5 deletions
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37
submodules/InstantPageUI/Sources/InstantPageV2Layout.swift
View file

@ -2966,6 +2966,33 @@ func v2FrameForLine(_ line: InstantPageTextLine, boundingWidth: CGFloat, alignme
return lineFrame
}
// Returns the leading-edge x offset (line-origin-relative) for an inline-attachment's string
// `range`, correct for both LTR and RTL runs. `CTLineGetOffsetForStringIndex` at the start index
// gives the glyph's LEFT edge in LTR text, but its RIGHT edge in RTL text (increasing string index
// moves leftward) — so using the start-index offset alone as the left edge shoves an RTL attachment
// ~one advance too far right. Taking the min of the start- and end-index offsets yields the true
// leading (left) edge in both directions. Mirrors `Display.TextNode`'s `addEmbeddedItem`, including
// the directional-boundary secondary-offset handling. For a pure-LTR line this returns exactly the
// start-index offset (primary == secondary, and start-offset < end-offset), so LTR layout is
// byte-identical to the previous single-offset behavior.
private func v2LeadingOffsetForRange(_ line: CTLine, range: NSRange) -> CGFloat {
var secondaryStartOffset: CGFloat = 0.0
let rawStartOffset = CTLineGetOffsetForStringIndex(line, range.location, &secondaryStartOffset)
var startOffset = rawStartOffset
if !rawStartOffset.isEqual(to: secondaryStartOffset) {
startOffset = secondaryStartOffset
}
var secondaryEndOffset: CGFloat = 0.0
let rawEndOffset = CTLineGetOffsetForStringIndex(line, range.location + range.length, &secondaryEndOffset)
var endOffset = rawEndOffset
if !rawEndOffset.isEqual(to: secondaryEndOffset) {
endOffset = secondaryEndOffset
}
return min(startOffset, endOffset)
}
private func v2LocalAttachmentBoundsForRange(_ range: NSRange, imageItems: [InstantPageTextImageItem], formulaItems: [InstantPageTextFormulaRun]) -> CGRect? {
var result: CGRect?
@ -3144,14 +3171,14 @@ func layoutTextItem(
string.enumerateAttributes(in: runRange, options: []) { attributes, range, _ in
if let id = attributes[NSAttributedString.Key.init(rawValue: InstantPageMediaIdAttribute)] as? Int64, let dimensions = attributes[NSAttributedString.Key.init(rawValue: InstantPageMediaDimensionsAttribute)] as? PixelDimensions {
let imageSize = dimensions.cgSize.fitted(CGSize(width: boundingWidth, height: boundingWidth))
let xOffset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, nil)
let xOffset = v2LeadingOffsetForRange(line, range: range)
pendingImages.append(PendingV2ImageAttachment(xOffset: xOffset, range: range, id: id, size: imageSize))
} else if let attachment = attributes[NSAttributedString.Key(rawValue: InstantPageFormulaAttribute)] as? InstantPageMathAttachment {
let xOffset = CTLineGetOffsetForStringIndex(line, range.location, nil)
let xOffset = v2LeadingOffsetForRange(line, range: range)
let baselineOffset = (attributes[NSAttributedString.Key.baselineOffset] as? CGFloat) ?? 0.0
pendingFormulas.append(PendingV2FormulaAttachment(xOffset: xOffset, range: range, attachment: attachment, baselineOffset: baselineOffset))
} else if let emoji = attributes[ChatTextInputAttributes.customEmoji] as? ChatTextInputTextCustomEmojiAttribute {
let xOffset = CTLineGetOffsetForStringIndex(line, range.location, nil)
let xOffset = v2LeadingOffsetForRange(line, range: range)
let font = (attributes[NSAttributedString.Key.font] as? UIFont) ?? UIFont.systemFont(ofSize: 17.0)
// Size the inline emoji to the font's line height (A + D = the true
// line-box height) plus a 4pt bump at the 17pt body font (scaled
@ -3363,7 +3390,7 @@ func layoutTextItem(
for emoji in pendingEmoji {
let localIndex = emoji.range.location - lineRange.location
if localIndex >= 0 && localIndex < rects.count {
let x = CTLineGetOffsetForStringIndex(line, emoji.range.location, nil)
let x = v2LeadingOffsetForRange(line, range: emoji.range)
// characterRects are baseline-relative (positive-up). The emoji cell is now
// centered on the font line box (see frame loop), so in baseline-relative
// coords it spans [fontLineHeight/2 − size/2, fontLineHeight/2 + size/2].
@ -3375,7 +3402,7 @@ func layoutTextItem(
for image in pendingImages {
let localIndex = image.range.location - lineRange.location
if localIndex >= 0 && localIndex < rects.count {
let x = CTLineGetOffsetForStringIndex(line, image.range.location, nil)
let x = v2LeadingOffsetForRange(line, range: image.range)
// Image cell is centered on the font line box (see frame loop). Baseline-relative
// cell spans [fontLineHeight/2 − height/2, fontLineHeight/2 + height/2]; the full
// width feeds the reveal cost map so the streaming cursor is charged the image's