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Add dynamic line height adjustment for multiline math display

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Replace fixed fontSize × 1.5 spacing with adaptive height calculation based
  on actual line content (ascent + descent), providing better visual spacing
  for expressions with varying content heights.
This commit is contained in:
Nicolas Guillot
2025-11-14 12:31:54 +01:00
parent ca0c3fbe07
commit b014be12b4
3 changed files with 326 additions and 33 deletions
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80
Sources/SwiftMath/MathRender/MTTypesetter.swift
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@@ -363,7 +363,9 @@ class MTTypesetter {
var cramped = false
var spaced = false
var maxWidth: CGFloat = 0 // Maximum width for line breaking, 0 means no constraint
var currentLineStartIndex: Int = 0 // Index in displayAtoms where current line starts
var minimumLineSpacing: CGFloat = 0 // Minimum spacing between lines (will be set based on fontSize)
static func createLineForMathList(_ mathList:MTMathList?, font:MTFont?, style:MTLineStyle) -> MTMathListDisplay? {
let finalizedList = mathList?.finalized
// default is not cramped, no width constraint
@@ -416,6 +418,9 @@ class MTTypesetter {
self.currentAtoms = [MTMathAtom]()
self.style = style
self.currentLineIndexRange = NSMakeRange(NSNotFound, NSNotFound);
self.currentLineStartIndex = 0
// Set minimum line spacing to 20% of fontSize for some breathing room
self.minimumLineSpacing = (font?.fontSize ?? 0) * 0.2
}
static func preprocessMathList(_ ml:MTMathList?) -> [MTMathAtom] {
@@ -602,10 +607,16 @@ class MTTypesetter {
// Flush the current line
self.addDisplayLine()
// Move down for new line
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height based on actual content
let lineHeight = calculateCurrentLineHeight()
// Move down for new line using dynamic height
currentPosition.y -= lineHeight
currentPosition.x = 0
// Update line start index for next line
currentLineStartIndex = displayAtoms.count
// Reset for new line
currentLine = NSMutableAttributedString()
currentAtoms = []
@@ -640,8 +651,41 @@ class MTTypesetter {
if currentLine.length > 0 {
self.addDisplayLine()
}
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height based on actual content
let lineHeight = calculateCurrentLineHeight()
// Move down for new line using dynamic height
currentPosition.y -= lineHeight
currentPosition.x = 0
// Update line start index for next line
currentLineStartIndex = displayAtoms.count
}
/// Calculate the height of the current line based on actual display heights
/// Returns the total height (max ascent + max descent) plus minimum spacing
func calculateCurrentLineHeight() -> CGFloat {
// If no displays added for current line, use default spacing
guard currentLineStartIndex < displayAtoms.count else {
return styleFont.fontSize * 1.5
}
var maxAscent: CGFloat = 0
var maxDescent: CGFloat = 0
// Iterate through all displays added for the current line
for i in currentLineStartIndex..<displayAtoms.count {
let display = displayAtoms[i]
maxAscent = max(maxAscent, display.ascent)
maxDescent = max(maxDescent, display.descent)
}
// Total line height = max ascent + max descent + minimum spacing
let lineHeight = maxAscent + maxDescent + minimumLineSpacing
// Ensure we have at least the baseline fontSize spacing for readability
return max(lineHeight, styleFont.fontSize * 1.2)
}
/// Estimate the width of an atom including its scripts (without actually creating the displays)
@@ -1190,9 +1234,11 @@ class MTTypesetter {
currentAtoms = [] // Approximate - we're splitting
self.addDisplayLine()
// Move down for new line
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height and move down for new line
let lineHeight = calculateCurrentLineHeight()
currentPosition.y -= lineHeight
currentPosition.x = 0
currentLineStartIndex = displayAtoms.count
// Remaining text includes everything after the earlier break
let remainingText = String(firstLineText.suffix(from: earlierBreakIndex)) +
@@ -1211,9 +1257,11 @@ class MTTypesetter {
currentAtoms = firstLineAtoms
self.addDisplayLine()
// Move down for new line and reset x position
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height and move down for new line
let lineHeight = calculateCurrentLineHeight()
currentPosition.y -= lineHeight
currentPosition.x = 0
currentLineStartIndex = displayAtoms.count
// Start the new line with the content after the break
let remainingText = String(currentText.suffix(from: breakIndex))
@@ -1239,8 +1287,10 @@ class MTTypesetter {
// If adding this scripted atom would exceed width, break line first
if projectedWidth > maxWidth {
self.addDisplayLine()
currentPosition.y -= styleFont.fontSize * 1.5
let lineHeight = calculateCurrentLineHeight()
currentPosition.y -= lineHeight
currentPosition.x = 0
currentLineStartIndex = displayAtoms.count
}
}
@@ -1433,9 +1483,11 @@ class MTTypesetter {
currentAtoms = []
self.addDisplayLine()
// Move down for new line
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height and move down for new line
let lineHeight = calculateCurrentLineHeight()
currentPosition.y -= lineHeight
currentPosition.x = 0
currentLineStartIndex = displayAtoms.count
// Remaining text includes everything after the earlier break
let remainingText = String(firstLineText.suffix(from: earlierBreakIndex)) +
@@ -1455,9 +1507,11 @@ class MTTypesetter {
currentAtoms = firstLineAtoms
self.addDisplayLine()
// Move down for new line and reset x position
currentPosition.y -= styleFont.fontSize * 1.5
// Calculate dynamic line height and move down for new line
let lineHeight = calculateCurrentLineHeight()
currentPosition.y -= lineHeight
currentPosition.x = 0
currentLineStartIndex = displayAtoms.count
// Start the new line with the content after the break
let remainingText = String(currentText.suffix(from: breakIndex))