Move Overscroll To TextView (#296)

### Description

The current overscroll behavior that was being handled in the
SourceEditor relied on a content inset, which was a little buggy and did
not allow the user to click in the over scrolled area to set the cursor.
This behavior was moved to TextView instead in order to fix this.

### Related Issues


### 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

---------

Co-authored-by: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>

Author: FastestMolasses

Sources/CodeEditSourceEditor/Controller/TextViewController+IndentLines.swift

@@ -1,12 +1,12 @@
 //
 //  TextViewController+IndentLines.swift
-//
+//  CodeEditTextView
 //
 //  Created by Ludwig, Tom on 11.09.24.
 //
 
-import CodeEditTextView
 import AppKit
+import CodeEditTextView
 
 extension TextViewController {
     /// Handles indentation and unindentation
@@ -23,7 +23,7 @@ extension TextViewController {
         guard !cursorPositions.isEmpty else { return }
 
         textView.undoManager?.beginUndoGrouping()
-for cursorPosition in self.cursorPositions.reversed() {
+        for cursorPosition in self.cursorPositions.reversed() {
             // get lineindex, i.e line-numbers+1
             guard let lineIndexes = getHighlightedLines(for: cursorPosition.range) else { continue }
 

Sources/CodeEditSourceEditor/Controller/TextViewController+StyleViews.swift

@@ -67,6 +67,6 @@ extension TextViewController {
         } else {
             scrollView.automaticallyAdjustsContentInsets = true
         }
-        scrollView.contentInsets.bottom = (contentInsets?.bottom ?? 0) + bottomContentInsets
+        scrollView.contentInsets.bottom = contentInsets?.bottom ?? 0
     }
 }

Sources/CodeEditSourceEditor/Controller/TextViewController.swift

@@ -104,7 +104,11 @@ public class TextViewController: NSViewController {
     ///
     /// Measured in a percentage of the view's total height, meaning a `0.3` value will result in overscroll
     /// of 1/3 of the view.
-    public var editorOverscroll: CGFloat
+    public var editorOverscroll: CGFloat {
+        didSet {
+            textView.overscrollAmount = editorOverscroll
+        }
+    }
 
     /// Whether the code editor should use the theme background color or be transparent
     public var useThemeBackground: Bool
@@ -183,18 +187,6 @@ public class TextViewController: NSViewController {
 
     internal var cancellables = Set<AnyCancellable>()
 
-    /// ScrollView's bottom inset using as editor overscroll
-    package var bottomContentInsets: CGFloat {
-        let height = view.frame.height
-        var inset = editorOverscroll * height
-
-        if height - inset < font.lineHeight * lineHeightMultiple {
-            inset = height - font.lineHeight * lineHeightMultiple
-        }
-
-        return max(inset, .zero)
-    }
-
     /// The trailing inset for the editor. Grows when line wrapping is disabled.
     package var textViewTrailingInset: CGFloat {
         // See https://github.com/CodeEditApp/CodeEditTextView/issues/66

Tests/CodeEditSourceEditorTests/TextViewControllerTests.swift

@@ -66,30 +66,19 @@ final class TextViewControllerTests: XCTestCase {
     // MARK: Overscroll
 
     func test_editorOverScroll() throws {
-        let scrollView = try XCTUnwrap(controller.view as? NSScrollView)
-        scrollView.frame = .init(x: .zero,
-                                 y: .zero,
-                                 width: 100,
-                                 height: 100)
-
         controller.editorOverscroll = 0
-        controller.contentInsets = nil
-        controller.reloadUI()
 
         // editorOverscroll: 0
-        XCTAssertEqual(scrollView.contentView.contentInsets.bottom, 0)
+        XCTAssertEqual(controller.textView.overscrollAmount, 0)
 
         controller.editorOverscroll = 0.5
-        controller.reloadUI()
 
         // editorOverscroll: 0.5
-        XCTAssertEqual(scrollView.contentView.contentInsets.bottom, 50.0)
+        XCTAssertEqual(controller.textView.overscrollAmount, 0.5)
 
         controller.editorOverscroll = 1.0
-        controller.reloadUI()
 
-        // editorOverscroll: 1.0
-        XCTAssertEqual(scrollView.contentView.contentInsets.bottom, 87.0)
+        XCTAssertEqual(controller.textView.overscrollAmount, 1.0)
     }
 
     // MARK: Insets
@@ -135,10 +124,10 @@ final class TextViewControllerTests: XCTestCase {
         // contentInsets: 16
         // editorOverscroll: 0.5
         controller.contentInsets = NSEdgeInsets(top: 16, left: 16, bottom: 16, right: 16)
-        controller.editorOverscroll = 0.5
+        controller.editorOverscroll = 0.5 // Should be ignored
         controller.reloadUI()
 
-        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 16, left: 16, bottom: 16 + 50, right: 16))
+        try assertInsetsEqual(scrollView.contentInsets, NSEdgeInsets(top: 16, left: 16, bottom: 16, right: 16))
         XCTAssertEqual(controller.gutterView.frame.origin.y, -16)
     }