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Fix large operator positioning causing incorrect atom ordering

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When rendering large operators (e.g., sum, integral) with scripts in text
  mode, the operator glyph was incorrectly positioned after its subscripts
  and superscripts instead of before them. This caused expressions like
  \sum_{i=1}^{n} i = \frac{n(n+1)}{2} to render with the equals sign
  appearing visually misplaced.

  Root cause:
  The line-breaking refactoring introduced double-positioning of large
  operators. makeLargeOp() internally sets the operator position, advances
  currentPosition.x, and adds script displays. However, the calling code
  then overwrote the position and advanced currentPosition.x again, causing:
  - Double-advancement leading to incorrect width calculations
  - Scripts positioned before the operator instead of after

  Solution:
  Save and restore typesetter state before/after line break dimension checks,
  then call makeLargeOp() once at the correct position after handling line
  breaks and inter-element spacing.
This commit is contained in:
Nicolas Guillot
2025-11-14 10:32:10 +01:00
parent 8cf87ef703
commit 15269e87e5
3 changed files with 276 additions and 56 deletions
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15
Sources/SwiftMath/MathRender/MTMathUILabel.swift
View File

@@ -258,9 +258,24 @@ public class MTMathUILabel : MTView {
let effectiveWidth = _preferredMaxLayoutWidth > 0 ? _preferredMaxLayoutWidth : bounds.size.width
let availableWidth = effectiveWidth - contentInsets.left - contentInsets.right
print("🔧 MTMathUILabel _layoutSubviews:")
print(" preferredMaxLayoutWidth: \(_preferredMaxLayoutWidth)")
print(" bounds.size.width: \(bounds.size.width)")
print(" effectiveWidth: \(effectiveWidth)")
print(" availableWidth: \(availableWidth)")
print(" LaTeX: \(_latex.prefix(60))...")
// print("Pre list = \(_mathList!)")
_displayList = MTTypesetter.createLineForMathList(_mathList, font: font, style: currentStyle, maxWidth: availableWidth)
_displayList!.textColor = textColor
print(" Display subDisplays count: \(_displayList!.subDisplays.count)")
for (index, subDisplay) in _displayList!.subDisplays.enumerated() {
print(" Display \(index): type=\(type(of: subDisplay)), x=\(subDisplay.position.x), width=\(subDisplay.width)")
if let lineDisplay = subDisplay as? MTCTLineDisplay {
print(" Content: '\(lineDisplay.attributedString?.string ?? "")'")
}
}
// print("Post list = \(_mathList!)")
var textX = CGFloat(0)
switch self.textAlignment {

115
Sources/SwiftMath/MathRender/MTTypesetter.swift
View File

@@ -626,7 +626,15 @@ class MTTypesetter {
display!.localTextColor = MTColor(fromHexString: colorAtom.colorString)
// Check if we need to break before adding this colored content
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:.ordinary)
@@ -643,7 +651,15 @@ class MTTypesetter {
display!.localTextColor = MTColor(fromHexString: colorAtom.colorString)
// Check if we need to break before adding this colored content
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else if prevNode != nil && display!.subDisplays.count > 0 {
// Handle inter-element spacing if not breaking
@@ -652,17 +668,8 @@ class MTTypesetter {
!ctLineDisplay.atoms.isEmpty {
let subDisplayAtom = ctLineDisplay.atoms[0]
let interElementSpace = self.getInterElementSpace(prevNode!.type, right:subDisplayAtom.type)
if currentLine.length > 0 {
if interElementSpace > 0 {
// add a kerning of that space to the previous character
currentLine.addAttribute(kCTKernAttributeName as NSAttributedString.Key,
value:NSNumber(floatLiteral: interElementSpace),
range:currentLine.mutableString.rangeOfComposedCharacterSequence(at: currentLine.length-1))
}
} else {
// increase the space
currentPosition.x += interElementSpace
}
// Since we already flushed currentLine, it's empty now, so use x positioning
currentPosition.x += interElementSpace
}
}
@@ -678,7 +685,15 @@ class MTTypesetter {
display!.localBackgroundColor = MTColor(fromHexString: colorboxAtom.colorString)
// Check if we need to break before adding this colorbox
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .ordinary)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:.ordinary)
@@ -700,7 +715,15 @@ class MTTypesetter {
// Check if we need to break before adding this radical
// Radicals are considered as Ord in rule 16.
if shouldBreakBeforeDisplay(displayRad!, prevNode: prevNode, displayType: .ordinary) {
let shouldBreak = shouldBreakBeforeDisplay(displayRad!, prevNode: prevNode, displayType: .ordinary)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:.ordinary)
@@ -724,7 +747,15 @@ class MTTypesetter {
let display = self.makeFraction(frac)
// Check if we need to break before adding this fraction
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: atom.type) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: atom.type)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:atom.type)
@@ -741,25 +772,37 @@ class MTTypesetter {
}
case .largeOperator:
// Create the large operator display first
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Create the large operator display to check if we need line breaking
let op = atom as! MTLargeOperator?
let display = self.makeLargeOp(op)
// Check if we need to break before adding this operator
// Large operators can be tall (with limits), so check both width and height
let isTooTall = (display!.ascent + display!.descent) > styleFont.fontSize * 2.5
let isTooWide = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: atom.type)
// Save state before creating display (makeLargeOp may add scripts to displayAtoms)
let savedDisplayAtomsCount = displayAtoms.count
let savedPosition = currentPosition
let tempDisplay = self.makeLargeOp(op)
let tempIsTooTall = (tempDisplay!.ascent + tempDisplay!.descent) > styleFont.fontSize * 2.5
let tempIsTooWide = shouldBreakBeforeDisplay(tempDisplay!, prevNode: prevNode, displayType: atom.type)
let shouldBreak = tempIsTooTall || tempIsTooWide
if isTooTall || isTooWide {
// Restore state (remove any scripts that were added)
displayAtoms.removeLast(displayAtoms.count - savedDisplayAtomsCount)
currentPosition = savedPosition
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:atom.type)
}
// Position and add the operator display
display!.position = currentPosition
// Now create the display at the correct position (after spacing/line break)
// makeLargeOp sets position, advances currentPosition.x, and adds scripts
let display = self.makeLargeOp(op)
displayAtoms.append(display!)
currentPosition.x += display!.width
case .inner:
// Create the inner display first
@@ -774,7 +817,15 @@ class MTTypesetter {
}
// Check if we need to break before adding this inner content
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .inner) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .inner)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:atom.type)
@@ -908,7 +959,15 @@ class MTTypesetter {
// Check if we need to break before adding this table
// We will consider tables as inner
if shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .inner) {
let shouldBreak = shouldBreakBeforeDisplay(display!, prevNode: prevNode, displayType: .inner)
// Flush current line to convert accumulated text to displays
if currentLine.length > 0 {
self.addDisplayLine()
}
// Perform line break if needed
if shouldBreak {
performLineBreak()
} else {
self.addInterElementSpace(prevNode, currentType:.inner)