Fix Cursor Lagging - Update Cursors in TextView.layout (#109)

### Description

Addresses an issue described by @nkleemann in the linked issue. The issue was a bug where cursors would lag behind an edit. This is due to the edited line's layout information being invalidated by the edit, meaning the selection manager cannot get valid layout information to position cursors.

This change puts a selection position update in the text view's `layout` call, after the layout manager has done it's layout pass. This ensures the selection manage is using valid layout information, fixing the lagging issue.

### Related Issues

* CodeEditApp/CodeEditSourceEditor#317

### 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

On v0.11.2:

https://github.com/user-attachments/assets/f4f23e02-58e5-410b-ba1a-0ea5e449dce4

With this change:

https://github.com/user-attachments/assets/663fdecb-c1dd-43ec-9990-5f8c7da07205

Author: thecoolwinter

Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager.swift

@@ -136,72 +136,80 @@ public class TextSelectionManager: NSObject {
 
     // MARK: - Selection Views
 
-    /// Update all selection cursors. Placing them in the correct position for each text selection and reseting the
-    /// blink timer.
-    func updateSelectionViews(force: Bool = false) {
+    /// Update all selection cursors. Placing them in the correct position for each text selection and
+    /// optionally reseting the blink timer.
+    func updateSelectionViews(force: Bool = false, skipTimerReset: Bool = false) {
         guard textView?.isFirstResponder ?? false else { return }
         var didUpdate: Bool = false
 
         for textSelection in textSelections {
             if textSelection.range.isEmpty {
-                guard let cursorRect = layoutManager?.rectForOffset(textSelection.range.location) else {
-                    continue
-                }
-
-                var doesViewNeedReposition: Bool
-
-                // If using the system cursor, macOS will change the origin and height by about 0.5, so we do an
-                // approximate equals in that case to avoid extra updates.
-                if useSystemCursor, #available(macOS 14.0, *) {
-                    doesViewNeedReposition = !textSelection.boundingRect.origin.approxEqual(cursorRect.origin)
-                    || !textSelection.boundingRect.height.approxEqual(layoutManager?.estimateLineHeight() ?? 0)
-                } else {
-                    doesViewNeedReposition = textSelection.boundingRect.origin != cursorRect.origin
-                    || textSelection.boundingRect.height != layoutManager?.estimateLineHeight() ?? 0
-                }
-
-                if textSelection.view == nil || doesViewNeedReposition {
-                    let cursorView: NSView
+                didUpdate = didUpdate || repositionCursorSelection(textSelection: textSelection)
+            } else if !textSelection.range.isEmpty && textSelection.view != nil {
+                textSelection.view?.removeFromSuperview()
+                textSelection.view = nil
+                didUpdate = true
+            }
+        }
 
-                    if let existingCursorView = textSelection.view {
-                        cursorView = existingCursorView
-                    } else {
-                        textSelection.view?.removeFromSuperview()
-                        textSelection.view = nil
+        if didUpdate || force {
+            delegate?.setNeedsDisplay()
+            if !skipTimerReset {
+                cursorTimer.resetTimer()
+                resetSystemCursorTimers()
+            }
+        }
+    }
 
-                        if useSystemCursor, #available(macOS 14.0, *) {
-                            let systemCursorView = NSTextInsertionIndicator(frame: .zero)
-                            cursorView = systemCursorView
-                            systemCursorView.displayMode = .automatic
-                        } else {
-                            let internalCursorView = CursorView(color: insertionPointColor)
-                            cursorView = internalCursorView
-                            cursorTimer.register(internalCursorView)
-                        }
+    private func repositionCursorSelection(textSelection: TextSelection) -> Bool {
+        guard let cursorRect = layoutManager?.rectForOffset(textSelection.range.location) else {
+            return false
+        }
 
-                        textView?.addSubview(cursorView, positioned: .above, relativeTo: nil)
-                    }
+        var doesViewNeedReposition: Bool
 
-                    cursorView.frame.origin = cursorRect.origin
-                    cursorView.frame.size.height = cursorRect.height
+        // If using the system cursor, macOS will change the origin and height by about 0.5, so we do an
+        // approximate equals in that case to avoid extra updates.
+        if useSystemCursor, #available(macOS 14.0, *) {
+            doesViewNeedReposition = !textSelection.boundingRect.origin.approxEqual(cursorRect.origin)
+            || !textSelection.boundingRect.height.approxEqual(layoutManager?.estimateLineHeight() ?? 0)
+        } else {
+            doesViewNeedReposition = textSelection.boundingRect.origin != cursorRect.origin
+            || textSelection.boundingRect.height != layoutManager?.estimateLineHeight() ?? 0
+        }
 
-                    textSelection.view = cursorView
-                    textSelection.boundingRect = cursorView.frame
+        if textSelection.view == nil || doesViewNeedReposition {
+            let cursorView: NSView
 
-                    didUpdate = true
-                }
-            } else if !textSelection.range.isEmpty && textSelection.view != nil {
+            if let existingCursorView = textSelection.view {
+                cursorView = existingCursorView
+            } else {
                 textSelection.view?.removeFromSuperview()
                 textSelection.view = nil
-                didUpdate = true
+
+                if useSystemCursor, #available(macOS 14.0, *) {
+                    let systemCursorView = NSTextInsertionIndicator(frame: .zero)
+                    cursorView = systemCursorView
+                    systemCursorView.displayMode = .automatic
+                } else {
+                    let internalCursorView = CursorView(color: insertionPointColor)
+                    cursorView = internalCursorView
+                    cursorTimer.register(internalCursorView)
+                }
+
+                textView?.addSubview(cursorView, positioned: .above, relativeTo: nil)
             }
-        }
 
-        if didUpdate || force {
-            delegate?.setNeedsDisplay()
-            cursorTimer.resetTimer()
-            resetSystemCursorTimers()
+            cursorView.frame.origin = cursorRect.origin
+            cursorView.frame.size.height = cursorRect.height
+
+            textSelection.view = cursorView
+            textSelection.boundingRect = cursorView.frame
+
+            return true
         }
+
+        return false
     }
 
     private func resetSystemCursorTimers() {

Sources/CodeEditTextView/TextView/TextView+Layout.swift

@@ -11,6 +11,7 @@ extension TextView {
     override public func layout() {
         super.layout()
         layoutManager.layoutLines()
+        selectionManager.updateSelectionViews(skipTimerReset: true)
     }
 
     open override class var isCompatibleWithResponsiveScrolling: Bool {