Start on Scrolling Offset

Author: thecoolwinter

Package.resolved

@@ -0,0 +1,22 @@
+//
+//  MinimapContentView.swift
+//  CodeEditSourceEditor
+//
+//  Created by Khan Winter on 4/11/25.
+//
+
+import AppKit
+
+final class MinimapContentView: FlippedNSView {
+    override func draw(_ dirtyRect: NSRect) {
+        guard let context = NSGraphicsContext.current?.cgContext else { return }
+        context.saveGState()
+
+        context.setFillColor(NSColor.separatorColor.cgColor)
+        context.fill([
+            CGRect(x: 0, y: 0, width: 1, height: frame.height)
+        ])
+
+        context.restoreGState()
+    }
+}

Sources/CodeEditSourceEditor/Minimap/MinimapContentView.swift

@@ -40,16 +40,22 @@ final class MinimapLineRenderer: TextLayoutManagerRenderDelegate {
         // Make all fragments 2px tall
         textLine.lineFragments.forEach { fragmentPosition in
             let remainingHeight = fragmentPosition.height - 3.0
-            textLine.lineFragments.update(
-                atOffset: fragmentPosition.range.location,
-                delta: 0,
-                deltaHeight: -remainingHeight
-            )
+            if remainingHeight != 0 {
+                textLine.lineFragments.update(
+                    atOffset: fragmentPosition.range.location,
+                    delta: 0,
+                    deltaHeight: -remainingHeight
+                )
+            }
             fragmentPosition.data.height = 2.0
             fragmentPosition.data.scaledHeight = 3.0
         }
     }
 
+    func estimatedLineHeight() -> CGFloat? {
+        3.0
+    }
+
     func lineFragmentView(for lineFragment: LineFragment) -> LineFragmentView {
         MinimapLineFragmentView(textStorage: textView?.textStorage)
     }

Sources/CodeEditSourceEditor/Minimap/MinimapLineRenderer.swift

@@ -0,0 +1,32 @@
+//
+//  MinimapView+DocumentVisibleView.swift
+//  CodeEditSourceEditor
+//
+//  Created by Khan Winter on 4/11/25.
+//
+
+import AppKit
+
+extension MinimapView {
+    func updateDocumentVisibleViewPosition() {
+        guard let textView = textView, let editorScrollView = textView.enclosingScrollView else { return }
+        layoutManager?.layoutLines(in: scrollView.documentVisibleRect)
+        let editorHeight = textView.frame.height
+        let minimapHeight = contentView.frame.height
+
+        let containerHeight = scrollView.documentVisibleRect.height
+        let scrollPercentage = (
+            editorScrollView.documentVisibleRect.origin.y + editorScrollView.contentInsets.top
+        ) / textView.frame.height
+//        let scrollOffset = editorScrollView.documentVisibleRect.origin.y
+
+//        let scrollMultiplier: CGFloat = if minimapHeight < containerHeight {
+//            1.0
+//        } else {
+//            1.0 - (minimapHeight - containerHeight) / (editorHeight - containerHeight)
+//        }
+
+        let newMinimapOrigin = minimapHeight * scrollPercentage
+        scrollView.contentView.bounds.origin.y = newMinimapOrigin - editorScrollView.contentInsets.top
+    }
+}

Sources/CodeEditSourceEditor/Minimap/MinimapView+DocumentVisibleView.swift

@@ -11,17 +11,40 @@ import CodeEditTextView
 class MinimapView: NSView {
     weak var textView: TextView?
 
+    /// The container scrollview for the minimap contents.
     let scrollView: NSScrollView
-    let contentView: FlippedNSView
+    /// The view text lines are rendered into.
+    let contentView: MinimapContentView
+    /// The box displaying the visible region on the minimap.
+    let documentVisibleView: NSView
+
+    /// The layout manager that uses the ``lineRenderer`` to render and layout lines.
     var layoutManager: TextLayoutManager?
+    /// A custom line renderer that lays out lines of text as 2px tall and draws contents as small lines
+    /// using ``MinimapLineFragmentView``
     let lineRenderer: MinimapLineRenderer
 
     var theme: EditorTheme {
         didSet {
+            documentVisibleView.layer?.backgroundColor = theme.text.color.withAlphaComponent(0.1).cgColor
             layer?.backgroundColor = theme.background.cgColor
         }
     }
 
+    var visibleTextRange: NSRange? {
+        guard let layoutManager = layoutManager else { return nil }
+        let minY = max(visibleRect.minY, 0)
+        let maxY = min(visibleRect.maxY, layoutManager.estimatedHeight())
+        guard let minYLine = layoutManager.textLineForPosition(minY),
+              let maxYLine = layoutManager.textLineForPosition(maxY) else {
+            return nil
+        }
+        return NSRange(
+            location: minYLine.range.location,
+            length: (maxYLine.range.location - minYLine.range.location) + maxYLine.range.length
+        )
+    }
+
     init(textView: TextView, theme: EditorTheme) {
         self.textView = textView
         self.theme = theme
@@ -34,12 +57,18 @@ class MinimapView: NSView {
         scrollView.drawsBackground = false
         scrollView.verticalScrollElasticity = .none
 
-        self.contentView = FlippedNSView(frame: .zero)
+        self.contentView = MinimapContentView(frame: .zero)
         contentView.translatesAutoresizingMaskIntoConstraints = false
 
+        self.documentVisibleView = NSView()
+        documentVisibleView.translatesAutoresizingMaskIntoConstraints = false
+        documentVisibleView.wantsLayer = true
+        documentVisibleView.layer?.backgroundColor = theme.text.color.withAlphaComponent(0.1).cgColor
+
         super.init(frame: .zero)
 
         addSubview(scrollView)
+        addSubview(documentVisibleView)
         scrollView.documentView = contentView
 
         self.translatesAutoresizingMaskIntoConstraints = false
@@ -58,6 +87,7 @@ class MinimapView: NSView {
         layer?.backgroundColor = theme.background.cgColor
 
         setUpConstraints()
+        setUpListeners()
     }
 
     private func setUpConstraints() {
@@ -67,10 +97,40 @@ class MinimapView: NSView {
             scrollView.leadingAnchor.constraint(equalTo: leadingAnchor),
             scrollView.trailingAnchor.constraint(equalTo: trailingAnchor),
 
-            contentView.widthAnchor.constraint(equalTo: widthAnchor)
+            contentView.widthAnchor.constraint(equalTo: widthAnchor),
+
+            documentVisibleView.leadingAnchor.constraint(equalTo: leadingAnchor),
+            documentVisibleView.trailingAnchor.constraint(equalTo: trailingAnchor)
         ])
     }
 
+    private func setUpListeners() {
+        guard let editorScrollView = textView?.enclosingScrollView else { return }
+        // Need to listen to:
+        // - ScrollView offset changed
+        // - ScrollView frame changed
+        // and update the document visible box to match.
+        NotificationCenter.default.addObserver(
+            forName: NSView.boundsDidChangeNotification,
+            object: editorScrollView.contentView,
+            queue: .main
+        ) { [weak self] _ in
+            // Scroll changed
+            self?.layoutManager?.layoutLines()
+            self?.updateDocumentVisibleViewPosition()
+        }
+
+        NotificationCenter.default.addObserver(
+            forName: NSView.frameDidChangeNotification,
+            object: editorScrollView.contentView,
+            queue: .main
+        ) { [weak self] _ in
+            // Frame changed
+            self?.layoutManager?.layoutLines()
+            self?.updateDocumentVisibleViewPosition()
+        }
+    }
+
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
@@ -86,18 +146,6 @@ class MinimapView: NSView {
         super.layout()
     }
 
-    override func draw(_ dirtyRect: NSRect) {
-        guard let context = NSGraphicsContext.current?.cgContext else { return }
-        context.saveGState()
-
-        context.setFillColor(NSColor.separatorColor.cgColor)
-        context.fill([
-            CGRect(x: 0, y: 0, width: 1, height: frame.height)
-        ])
-
-        context.restoreGState()
-    }
-
     override func hitTest(_ point: NSPoint) -> NSView? {
         if visibleRect.contains(point) {
             return self