From 7d2412c053f284b95befeb67a2a9f5f7e755bff4 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Wed, 21 Feb 2024 12:26:44 -0600
Subject: [PATCH] General Performance Improvements (#24)

---
 .../CodeEditTextView/Cursors/CursorView.swift |  2 ++
 .../TextLayoutManager/TextLayoutManager.swift | 24 +++++++++++++++----
 .../TextLine/LineFragmentView.swift           |  2 ++
 .../CodeEditTextView/TextView/TextView.swift  | 10 +++-----
 .../Utils/ViewReuseQueue.swift                |  2 +-
 5 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/Sources/CodeEditTextView/Cursors/CursorView.swift b/Sources/CodeEditTextView/Cursors/CursorView.swift
index 105209a7..166e9ded 100644
--- a/Sources/CodeEditTextView/Cursors/CursorView.swift
+++ b/Sources/CodeEditTextView/Cursors/CursorView.swift
@@ -25,6 +25,8 @@ open class CursorView: NSView {
         true
     }
 
+    override open func hitTest(_ point: NSPoint) -> NSView? { nil }
+
     /// Create a cursor view.
     /// - Parameters:
     ///   - blinkDuration: The duration to blink, leave as nil to never blink.
diff --git a/Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager.swift b/Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager.swift
index 0cc69376..11ce033d 100644
--- a/Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager.swift
+++ b/Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager.swift
@@ -54,6 +54,17 @@ public class TextLayoutManager: NSObject {
         }
     }
 
+    /// The amount of extra vertical padding used to lay out lines in before they come into view.
+    ///
+    /// This solves a small problem with layout performance, if you're seeing layout lagging behind while scrolling,
+    /// adjusting this value higher may help fix that.
+    /// Defaults to `350`.
+    public var verticalLayoutPadding: CGFloat = 350 {
+        didSet {
+            setNeedsLayout()
+        }
+    }
+
     // MARK: - Internal
 
     weak var textStorage: NSTextStorage?
@@ -215,10 +226,12 @@ public class TextLayoutManager: NSObject {
     }
 
     /// Ends a transaction. When called, the layout manager will layout any necessary lines.
-    public func endTransaction() {
+    public func endTransaction(forceLayout: Bool = false) {
         transactionCounter -= 1
         if transactionCounter == 0 {
-            setNeedsLayout()
+            if forceLayout {
+                setNeedsLayout()
+            }
             layoutLines()
         } else if transactionCounter < 0 {
             // swiftlint:disable:next line_length
@@ -237,8 +250,8 @@ public class TextLayoutManager: NSObject {
             return
         }
         CATransaction.begin()
-        let minY = max(visibleRect.minY, 0)
-        let maxY = max(visibleRect.maxY, 0)
+        let minY = max(visibleRect.minY - verticalLayoutPadding, 0)
+        let maxY = max(visibleRect.maxY + verticalLayoutPadding, 0)
         let originalHeight = lineStorage.height
         var usedFragmentIDs = Set<UUID>()
         var forceLayout: Bool = needsLayout
@@ -283,6 +296,8 @@ public class TextLayoutManager: NSObject {
             newVisibleLines.insert(linePosition.data.id)
         }
 
+        CATransaction.commit()
+
         // Enqueue any lines not used in this layout pass.
         viewReuseQueue.enqueueViews(notInSet: usedFragmentIDs)
 
@@ -302,7 +317,6 @@ public class TextLayoutManager: NSObject {
         }
 
         needsLayout = false
-        CATransaction.commit()
     }
 
     /// Lays out a single text line.
diff --git a/Sources/CodeEditTextView/TextLine/LineFragmentView.swift b/Sources/CodeEditTextView/TextLine/LineFragmentView.swift
index 485b303d..043c1829 100644
--- a/Sources/CodeEditTextView/TextLine/LineFragmentView.swift
+++ b/Sources/CodeEditTextView/TextLine/LineFragmentView.swift
@@ -20,6 +20,8 @@ final class LineFragmentView: NSView {
         false
     }
 
+    override func hitTest(_ point: NSPoint) -> NSView? { nil }
+
     /// Prepare the view for reuse, clears the line fragment reference.
     override func prepareForReuse() {
         super.prepareForReuse()
diff --git a/Sources/CodeEditTextView/TextView/TextView.swift b/Sources/CodeEditTextView/TextView/TextView.swift
index dc34b96c..e7a4a6a7 100644
--- a/Sources/CodeEditTextView/TextView/TextView.swift
+++ b/Sources/CodeEditTextView/TextView/TextView.swift
@@ -381,15 +381,11 @@ public class TextView: NSView, NSTextContent {
     /// - Parameter point: The point to find.
     /// - Returns: A view at the given point, if any.
     override public func hitTest(_ point: NSPoint) -> NSView? {
-        // For our purposes, cursor and line fragment views should be transparent from the point of view of
-        // all other views. So, if the normal hitTest returns one of them, we return `self` instead.
-        let hitView = super.hitTest(point)
-
-        if let hitView, hitView != self,
-            type(of: hitView) == CursorView.self || type(of: hitView) == LineFragmentView.self {
+        if visibleRect.contains(point) {
             return self
+        } else {
+            return super.hitTest(point)
         }
-        return hitView
     }
 
     // MARK: - Key Down
diff --git a/Sources/CodeEditTextView/Utils/ViewReuseQueue.swift b/Sources/CodeEditTextView/Utils/ViewReuseQueue.swift
index 6e44bf30..c969c573 100644
--- a/Sources/CodeEditTextView/Utils/ViewReuseQueue.swift
+++ b/Sources/CodeEditTextView/Utils/ViewReuseQueue.swift
@@ -52,7 +52,7 @@ public class ViewReuseQueue<View: NSView, Key: Hashable> {
     /// Enqueues all views not in the given set.
     /// - Parameter outsideSet: The keys who's views should not be enqueued for reuse.
     public func enqueueViews(notInSet keys: Set<Key>) {
-        // Get all keys that are in "use" but not in the given set.
+        // Get all keys that are currently in "use" but not in the given set, and enqueue them for reuse.
         for key in Set(usedViews.keys).subtracting(keys) {
             enqueueView(forKey: key)
         }