fix(datagrid): size the two-line header from font metrics so title and comment never overlap

The captured single-line height could come back smaller than the title
glyphs, collapsing the name band into the comment line. Drive the header
height and the name band from fixed font-derived metrics instead.

Claude-Session: https://claude.ai/code/session_0198faM6VCrViRU4XwRoS1DC

Author: datlechin

TablePro/Views/Results/SortableHeaderCell.swift

@@ -23,7 +23,10 @@ final class SortableHeaderCell: NSTableHeaderCell {
     private static let funnelSize = NSSize(width: 13, height: 13)
     private static let funnelPointSize: CGFloat = 11
     private static let subtitleFont = NSFont.systemFont(ofSize: NSFont.smallSystemFontSize - 1)
+    private static let titleMetricFont = NSFont.systemFont(ofSize: NSFont.smallSystemFontSize)
+    static let titleBandHeight: CGFloat = ceil(SortableHeaderCell.titleMetricFont.boundingRectForFont.height) + 6
     static let commentBandHeight: CGFloat = ceil(SortableHeaderCell.subtitleFont.boundingRectForFont.height) + 4
+    static let twoLineHeaderHeight: CGFloat = SortableHeaderCell.titleBandHeight + SortableHeaderCell.commentBandHeight
 
     override init(textCell string: String) {
         super.init(textCell: string)
@@ -107,7 +110,7 @@ final class SortableHeaderCell: NSTableHeaderCell {
 
     func nameBandRect(forBounds rect: NSRect) -> NSRect {
         guard isTwoLineLayout else { return rect }
-        let bandHeight = max(0, rect.height - Self.commentBandHeight)
+        let bandHeight = min(rect.height, Self.titleBandHeight)
         return NSRect(x: rect.minX, y: rect.minY, width: rect.width, height: bandHeight)
     }
 

TablePro/Views/Results/SortableHeaderView.swift

@@ -70,7 +70,6 @@ final class SortableHeaderView: NSTableHeaderView {
     private var dragOccurredDuringClick = false
     private var mouseMovedTrackingArea: NSTrackingArea?
     private var hoveredColumnIndex: Int?
-    private var baseHeight: CGFloat = 0
 
     var showsCommentLine: Bool = false {
         didSet {
@@ -82,20 +81,17 @@ final class SortableHeaderView: NSTableHeaderView {
 
     override init(frame frameRect: NSRect) {
         super.init(frame: frameRect)
-        baseHeight = frameRect.height
     }
 
     required init?(coder: NSCoder) {
         super.init(coder: coder)
-        baseHeight = frame.height
     }
 
     override func setFrameSize(_ newSize: NSSize) {
-        if baseHeight <= 0 {
-            baseHeight = newSize.height
-        }
         var size = newSize
-        size.height = showsCommentLine ? baseHeight + SortableHeaderCell.commentBandHeight : baseHeight
+        if showsCommentLine {
+            size.height = max(newSize.height, SortableHeaderCell.twoLineHeaderHeight)
+        }
         super.setFrameSize(size)
     }
 

TableProTests/Views/Results/SortableHeaderCellTests.swift

@@ -70,13 +70,14 @@ struct SortableHeaderCellTests {
     func twoLineLayoutReservesCommentBandBelowName() {
         let cell = SortableHeaderCell(textCell: "id")
         cell.isTwoLineLayout = true
-        let bounds = NSRect(x: 0, y: 0, width: 100, height: 38)
+        let bounds = NSRect(x: 0, y: 0, width: 100, height: SortableHeaderCell.twoLineHeaderHeight)
 
         let nameBand = cell.nameBandRect(forBounds: bounds)
 
         #expect(nameBand.minY == bounds.minY)
-        #expect(nameBand.height == bounds.height - SortableHeaderCell.commentBandHeight)
+        #expect(nameBand.height == SortableHeaderCell.titleBandHeight)
         #expect(nameBand.maxY < bounds.maxY)
+        #expect(bounds.maxY - nameBand.maxY == SortableHeaderCell.commentBandHeight)
     }
 
     @Test("Funnel aligns to the name band in a two-line header")