Add contentInsets Parameter (CodeEditApp#141)

# Description

This PR adds a `contentInsets` parameter that lets users set an inset
object for the editor. It also updates `STTextView` to be able to set
the left inset correctly. When left `nil` the scroll view will use
automatic insets.

This also doesn't override the overscroll option, but rather adds the
overscroll after the insets are applied.

# Related Issues

- [Discord
discussion](https://canary.discord.com/channels/951544472238444645/954084547694325861/1075085722211581952)
- [STTextView
commit](krzyzanowskim/STTextView@06d8f33)

# Screenshots

Adding top and left insets:
<img width="741" alt="Screenshot 2023-02-14 at 3 09 57 PM"
src="https://user-images.githubusercontent.com/35942988/218863914-8869e185-cd21-45a7-a7aa-58387ea778ea.png">

Adding left and bottom insets (scroller is also inset):
<img width="835" alt="Screenshot 2023-02-14 at 3 10 15 PM"
src="https://user-images.githubusercontent.com/35942988/218863899-99d2b124-fc96-418a-9869-d6897a7baea4.png">

Package.swift

@@ -15,7 +15,7 @@ let package = Package(
     dependencies: [
         .package(
             url: "https://github.com/krzyzanowskim/STTextView.git",
-            exact: "0.4.0"
+            from: "0.4.1"
         ),
         .package(
             url: "https://github.com/CodeEditApp/CodeEditLanguages.git",

Sources/CodeEditTextView/CodeEditTextView.swift

@@ -25,6 +25,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     ///   - editorOverscroll: The percentage for overscroll, between 0-1 (default: `0.0`)
     ///   - highlightProvider: A class you provide to perform syntax highlighting. Leave this as `nil` to use the
     ///                        built-in `TreeSitterClient` highlighter.
+    ///   - contentInsets: Insets to use to offset the content in the enclosing scroll view. Leave as `nil` to let the
+    ///                    scroll view automatically adjust content insets.
     public init(
         _ text: Binding<String>,
         language: CodeLanguage,
@@ -36,7 +38,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         editorOverscroll: Binding<Double> = .constant(0.0),
         cursorPosition: Published<(Int, Int)>.Publisher? = nil,
         useThemeBackground: Bool = true,
-        highlightProvider: HighlightProviding? = nil
+        highlightProvider: HighlightProviding? = nil,
+        contentInsets: NSEdgeInsets? = nil
     ) {
         self._text = text
         self.language = language
@@ -49,6 +52,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         self._editorOverscroll = editorOverscroll
         self.cursorPosition = cursorPosition
         self.highlightProvider = highlightProvider
+        self.contentInsets = contentInsets
     }
 
     @Binding private var text: String
@@ -62,6 +66,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     private var cursorPosition: Published<(Int, Int)>.Publisher?
     private var useThemeBackground: Bool
     private var highlightProvider: HighlightProviding?
+    private var contentInsets: NSEdgeInsets?
 
     public typealias NSViewControllerType = STTextViewController
 
@@ -76,7 +81,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
             cursorPosition: cursorPosition,
             editorOverscroll: editorOverscroll,
             useThemeBackground: useThemeBackground,
-            highlightProvider: highlightProvider
+            highlightProvider: highlightProvider,
+            contentInsets: contentInsets
         )
         controller.lineHeightMultiple = lineHeight
         return controller
@@ -89,6 +95,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         controller.useThemeBackground = useThemeBackground
         controller.lineHeightMultiple = lineHeight
         controller.editorOverscroll = editorOverscroll
+        controller.contentInsets = contentInsets
 
         // Updating the language and theme needlessly can cause highlights to be re-calculated.
         if controller.language.id != language.id {

Sources/CodeEditTextView/STTextViewController.swift

@@ -55,6 +55,9 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     /// Filters used when applying edits..
     internal var textFilters: [TextFormation.Filter] = []
 
+    /// Optional insets to offset the text view in the scroll view by.
+    public var contentInsets: NSEdgeInsets?
+
     // MARK: - Highlighting
 
     internal var highlighter: Highlighter?
@@ -77,7 +80,8 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         cursorPosition: Published<(Int, Int)>.Publisher? = nil,
         editorOverscroll: Double,
         useThemeBackground: Bool,
-        highlightProvider: HighlightProviding? = nil
+        highlightProvider: HighlightProviding? = nil,
+        contentInsets: NSEdgeInsets? = nil
     ) {
         self.text = text
         self.language = language
@@ -89,6 +93,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         self.editorOverscroll = editorOverscroll
         self.useThemeBackground = useThemeBackground
         self.highlightProvider = highlightProvider
+        self.contentInsets = contentInsets
         super.init(nibName: nil, bundle: nil)
     }
 
@@ -98,6 +103,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
 
     // MARK: VC Lifecycle
 
+    // swiftlint:disable function_body_length
     public override func loadView() {
         textView = STTextView()
 
@@ -106,6 +112,10 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         scrollView.hasVerticalScroller = true
         scrollView.documentView = textView
         scrollView.drawsBackground = useThemeBackground
+        scrollView.automaticallyAdjustsContentInsets = contentInsets == nil
+        if let contentInsets = contentInsets {
+            scrollView.contentInsets = contentInsets
+        }
 
         rulerView = STLineNumberRulerView(textView: textView, scrollView: scrollView)
         rulerView.backgroundColor = useThemeBackground ? theme.background : .clear
@@ -218,9 +228,14 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         rulerView?.separatorColor = theme.invisibles
         rulerView?.baselineOffset = baselineOffset
 
-        (view as? NSScrollView)?.drawsBackground = useThemeBackground
-        (view as? NSScrollView)?.backgroundColor = useThemeBackground ? theme.background : .clear
-        (view as? NSScrollView)?.contentView.contentInsets.bottom = bottomContentInsets
+        if let scrollView = view as? NSScrollView {
+            scrollView.drawsBackground = useThemeBackground
+            scrollView.backgroundColor = useThemeBackground ? theme.background : .clear
+            if let contentInsets = contentInsets {
+                scrollView.contentInsets = contentInsets
+            }
+            scrollView.contentInsets.bottom = bottomContentInsets + (contentInsets?.bottom ?? 0)
+        }
 
         setStandardAttributes()
     }

Tests/CodeEditTextViewTests/STTextViewControllerTests.swift

@@ -70,6 +70,10 @@ final class STTextViewControllerTests: XCTestCase {
                                  width: 100,
                                  height: 100)
 
+        controller.editorOverscroll = 0
+        controller.contentInsets = nil
+        controller.reloadUI()
+
         // editorOverscroll: 0
         XCTAssertEqual(scrollView.contentView.contentInsets.bottom, 0)
 
@@ -86,6 +90,48 @@ final class STTextViewControllerTests: XCTestCase {
         XCTAssertEqual(scrollView.contentView.contentInsets.bottom, 87.0)
     }
 
+    func test_editorInsets() throws {
+        let scrollView = try XCTUnwrap(controller.view as? NSScrollView)
+        scrollView.frame = .init(x: .zero,
+                                 y: .zero,
+                                 width: 100,
+                                 height: 100)
+
+        func assertInsetsEqual(_ lhs: NSEdgeInsets, _ rhs: NSEdgeInsets) throws {
+            XCTAssertEqual(lhs.top, rhs.top)
+            XCTAssertEqual(lhs.right, rhs.right)
+            XCTAssertEqual(lhs.bottom, rhs.bottom)
+            XCTAssertEqual(lhs.left, rhs.left)
+        }
+
+        controller.editorOverscroll = 0
+        controller.contentInsets = nil
+        controller.reloadUI()
+
+        // contentInsets: 0
+        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 0, left: 0, bottom: 0, right: 0))
+
+        // contentInsets: 16
+        controller.contentInsets = NSEdgeInsets(top: 16, left: 16, bottom: 16, right: 16)
+        controller.reloadUI()
+
+        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 16, left: 16, bottom: 16, right: 16))
+
+        // contentInsets: different
+        controller.contentInsets = NSEdgeInsets(top: 32.5, left: 12.3, bottom: 20, right: 1)
+        controller.reloadUI()
+
+        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 32.5, left: 12.3, bottom: 20, right: 1))
+
+        // contentInsets: 16
+        // editorOverscroll: 0.5
+        controller.contentInsets = NSEdgeInsets(top: 16, left: 16, bottom: 16, right: 16)
+        controller.editorOverscroll = 0.5
+        controller.reloadUI()
+
+        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 16, left: 16, bottom: 16 + 50, right: 16))
+    }
+
     func test_editorOverScroll_ZeroCondition() throws {
         let scrollView = try XCTUnwrap(controller.view as? NSScrollView)
         scrollView.frame = .zero