Fix Gutter Position On Small Documents (#312)

### Description

Fixes an issue where on small documents the text view / scroll view
would get messed up when placing the gutter view relative to the top
padding. This makes the y position relative to the text view's y
position.

### Related Issues

* N/A

### Checklist

- [x] I read and understood the [contributing
guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md)
as well as the [code of
conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md)
- [x] The issues this PR addresses are related to each other
- [x] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] My changes are all related to the related issue above
- [x] I documented my code

### Screenshots

Before, would only appear on small files (1-3 lines):

![Screenshot 2025-04-22 at 10 40
16 AM](https://github.com/user-attachments/assets/fbade1e5-200d-4e46-8b6a-bcd6145ec7b7)

After:

![Screenshot 2025-04-22 at 10 36
08 AM](https://github.com/user-attachments/assets/46963668-af4c-42f8-a83f-01c7404589bb)

Author: thecoolwinter

Sources/CodeEditSourceEditor/Controller/TextViewController+LoadView.swift

@@ -23,10 +23,7 @@ extension TextViewController {
             delegate: self
         )
         gutterView.updateWidthIfNeeded()
-        scrollView.addFloatingSubview(
-            gutterView,
-            for: .horizontal
-        )
+        scrollView.addFloatingSubview(gutterView, for: .horizontal)
 
         minimapView = MinimapView(textView: textView, theme: theme)
         scrollView.addFloatingSubview(minimapView, for: .vertical)
@@ -89,7 +86,7 @@ extension TextViewController {
             minimapView.bottomAnchor.constraint(equalTo: scrollView.contentView.bottomAnchor),
             minimapXConstraint,
             maxWidthConstraint,
-            relativeWidthConstraint,
+            relativeWidthConstraint
         ])
     }
 
@@ -124,7 +121,11 @@ extension TextViewController {
             queue: .main
         ) { [weak self] _ in
             self?.gutterView.frame.size.height = (self?.textView.frame.height ?? 0) + 10
+            self?.gutterView.frame.origin.y = (self?.textView.frame.origin.y ?? 0.0)
+            - (self?.scrollView.contentInsets.top ?? 0)
+
             self?.gutterView.needsDisplay = true
+            self?.scrollView.needsLayout = true
         }
 
         NotificationCenter.default.addObserver(
@@ -146,7 +147,7 @@ extension TextViewController {
 
                     // Reset content insets and gutter position when appearance changes
                     self.styleScrollView()
-                    self.gutterView.frame.origin.y = -self.scrollView.contentInsets.top
+                    self.gutterView.frame.origin.y = self.textView.frame.origin.y - self.scrollView.contentInsets.top
                 }
             }
             .store(in: &cancellables)

Sources/CodeEditSourceEditor/Controller/TextViewController+StyleViews.swift

@@ -102,7 +102,7 @@ extension TextViewController {
 
         findViewController?.topPadding = contentInsets?.top
 
-        gutterView.frame.origin.y = -scrollView.contentInsets.top
+        gutterView.frame.origin.y = textView.frame.origin.y - scrollView.contentInsets.top
 
         // Update scrollview tiling
         scrollView.reflectScrolledClipView(scrollView.contentView)

Sources/CodeEditSourceEditor/Gutter/GutterView.swift

@@ -45,7 +45,11 @@ public class GutterView: NSView {
     var textColor: NSColor = .secondaryLabelColor
 
     @Invalidating(.display)
-    var font: NSFont = .systemFont(ofSize: 13)
+    var font: NSFont = .systemFont(ofSize: 13) {
+        didSet {
+            updateFontLineHeight()
+        }
+    }
 
     @Invalidating(.display)
     var edgeInsets: EdgeInsets = EdgeInsets(leading: 20, trailing: 12)
@@ -74,6 +78,19 @@ public class GutterView: NSView {
     /// The maximum number of digits found for a line number.
     private var maxLineLength: Int = 0
 
+    private var fontLineHeight = 1.0
+
+    private func updateFontLineHeight() {
+        let string = NSAttributedString(string: "0", attributes: [.font: font])
+        let typesetter = CTTypesetterCreateWithAttributedString(string)
+        let ctLine = CTTypesetterCreateLine(typesetter, CFRangeMake(0, 1))
+        var ascent: CGFloat = 0
+        var descent: CGFloat = 0
+        var leading: CGFloat = 0
+        CTLineGetTypographicBounds(ctLine, &ascent, &descent, &leading)
+        fontLineHeight = (ascent + descent + leading)
+    }
+
     override public var isFlipped: Bool {
         true
     }
@@ -181,7 +198,7 @@ public class GutterView: NSView {
                     y: line.yPos,
                     width: width,
                     height: line.height
-                )
+                ).pixelAligned
             )
         }
 
@@ -217,12 +234,16 @@ public class GutterView: NSView {
             let fragment: LineFragment? = linePosition.data.lineFragments.first?.data
             var ascent: CGFloat = 0
             let lineNumberWidth = CTLineGetTypographicBounds(ctLine, &ascent, nil, nil)
+            let fontHeightDifference = ((fragment?.height ?? 0) - fontLineHeight) / 4
 
-            let yPos = linePosition.yPos + ascent + (fragment?.heightDifference ?? 0)/2
+            let yPos = linePosition.yPos + ascent + (fragment?.heightDifference ?? 0)/2 + fontHeightDifference
             // Leading padding + (width - linewidth)
             let xPos = edgeInsets.leading + (maxWidth - lineNumberWidth)
 
-            context.textPosition = CGPoint(x: xPos, y: yPos).pixelAligned
+            ContextSetHiddenSmoothingStyle(context, 16)
+
+            context.textPosition = CGPoint(x: xPos, y: yPos)
+
             CTLineDraw(ctLine, context)
         }
         context.restoreGState()