From c711521b1f596e8a193fddf8954cdaae10bffdca Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Thu, 12 Jan 2023 06:47:20 +0000
Subject: [PATCH] Remove `NSLayoutManager`

---
 .../CodeEditTextView/CodeEditTextView.swift   | 11 +++++--
 .../NSRange+/NSRange+NSTextRange.swift        | 13 ++++++++
 .../STTextView+/STTextView+VisibleRange.swift | 30 ++++++++++++-------
 .../Highlighting/HighlightRange.swift         |  2 +-
 .../Highlighting/Highlighter.swift            | 12 ++++++--
 5 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/Sources/CodeEditTextView/CodeEditTextView.swift b/Sources/CodeEditTextView/CodeEditTextView.swift
index 3cb9823ca..0030d4fa6 100644
--- a/Sources/CodeEditTextView/CodeEditTextView.swift
+++ b/Sources/CodeEditTextView/CodeEditTextView.swift
@@ -73,12 +73,19 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
 
     public func updateNSViewController(_ controller: NSViewControllerType, context: Context) {
         controller.font = font
-        controller.language = language
-        controller.theme = theme
         controller.tabWidth = tabWidth
         controller.wrapLines = wrapLines
         controller.lineHeightMultiple = lineHeight
         controller.editorOverscroll = editorOverscroll
+
+        // Updating the language and theme needlessly can cause highlights to be re-calculated.
+        if controller.language.id != language.id {
+            controller.language = language
+        }
+        if controller.theme != theme {
+            controller.theme = theme
+        }
+
         controller.reloadUI()
         return
     }
diff --git a/Sources/CodeEditTextView/Extensions/NSRange+/NSRange+NSTextRange.swift b/Sources/CodeEditTextView/Extensions/NSRange+/NSRange+NSTextRange.swift
index a9a0a8737..daaee99c1 100644
--- a/Sources/CodeEditTextView/Extensions/NSRange+/NSRange+NSTextRange.swift
+++ b/Sources/CodeEditTextView/Extensions/NSRange+/NSRange+NSTextRange.swift
@@ -21,4 +21,17 @@ public extension NSTextRange {
 
         self.init(location: start, end: end)
     }
+
+    /// Creates an `NSRange` using document information from the given provider.
+    /// - Parameter provider: The `NSTextElementProvider` to use to convert this range into an `NSRange`
+    /// - Returns: An `NSRange` if possible
+    func nsRange(using provider: NSTextElementProvider) -> NSRange? {
+        guard let location = provider.offset?(from: provider.documentRange.location, to: location) else {
+            return nil
+        }
+        guard let length = provider.offset?(from: self.location, to: endLocation) else {
+            return nil
+        }
+        return NSRange(location: location, length: length)
+    }
 }
diff --git a/Sources/CodeEditTextView/Extensions/STTextView+/STTextView+VisibleRange.swift b/Sources/CodeEditTextView/Extensions/STTextView+/STTextView+VisibleRange.swift
index d6bb88bd6..476e953d8 100644
--- a/Sources/CodeEditTextView/Extensions/STTextView+/STTextView+VisibleRange.swift
+++ b/Sources/CodeEditTextView/Extensions/STTextView+/STTextView+VisibleRange.swift
@@ -7,22 +7,32 @@
 
 import Foundation
 import STTextView
+import AppKit
 
 extension STTextView {
-    func textRange(for rect: CGRect) -> NSRange {
-        let length = self.textContentStorage.textStorage?.length ?? 0
+    /// A helper for calculating the visible range on the text view with some small vertical padding.
+    var visibleTextRange: NSRange? {
+        // This helper finds the visible rect of the text using the enclosing scroll view, then finds the nearest
+        // `NSTextElement`s to those points and uses those elements to create the returned range.
 
-        guard let layoutManager = self.textContainer.layoutManager else {
-            return NSRange(0..<length)
+        // Get visible rect
+        guard let bounds = enclosingScrollView?.documentVisibleRect else {
+            return textLayoutManager.documentRange.nsRange(using: textContentStorage)
         }
-        let container = self.textContainer
 
-        let glyphRange = layoutManager.glyphRange(forBoundingRect: rect, in: container)
+        // Calculate min & max points w/ a small amount of padding vertically.
+        let minPoint = CGPoint(x: bounds.minX,
+                               y: bounds.minY - 100)
+        let maxPoint = CGPoint(x: bounds.maxX,
+                               y: bounds.maxY + 100)
 
-        return layoutManager.characterRange(forGlyphRange: glyphRange, actualGlyphRange: nil)
-    }
+        // Get text fragments for both the min and max points
+        guard let start = textLayoutManager.textLayoutFragment(for: minPoint)?.rangeInElement.location,
+              let end = textLayoutManager.textLayoutFragment(for: maxPoint)?.rangeInElement.endLocation else {
+            return textLayoutManager.documentRange.nsRange(using: textContentStorage)
+        }
 
-    var visibleTextRange: NSRange {
-        return textRange(for: visibleRect)
+        // Calculate a range and return it as an `NSRange`
+        return NSTextRange(location: start, end: end)?.nsRange(using: textContentStorage)
     }
 }
diff --git a/Sources/CodeEditTextView/Highlighting/HighlightRange.swift b/Sources/CodeEditTextView/Highlighting/HighlightRange.swift
index 7ba1bab67..00ba96946 100644
--- a/Sources/CodeEditTextView/Highlighting/HighlightRange.swift
+++ b/Sources/CodeEditTextView/Highlighting/HighlightRange.swift
@@ -1,6 +1,6 @@
 //
 //  HighlightRange.swift
-//  
+//
 //
 //  Created by Khan Winter on 9/14/22.
 //
diff --git a/Sources/CodeEditTextView/Highlighting/Highlighter.swift b/Sources/CodeEditTextView/Highlighting/Highlighter.swift
index 3e2e07e2d..9e260ec3f 100644
--- a/Sources/CodeEditTextView/Highlighting/Highlighter.swift
+++ b/Sources/CodeEditTextView/Highlighting/Highlighter.swift
@@ -42,7 +42,10 @@ class Highlighter: NSObject {
 
     /// The set of visible indexes in tht text view
     lazy private var visibleSet: IndexSet = {
-        return IndexSet(integersIn: Range(textView.visibleTextRange)!)
+        guard let range = textView.visibleTextRange else {
+            return IndexSet()
+        }
+        return IndexSet(integersIn: Range(range)!)
     }()
 
     // MARK: - UI
@@ -184,6 +187,11 @@ private extension Highlighter {
             // Loop through each highlight and modify the textStorage accordingly.
             textView.textContentStorage.textStorage?.beginEditing()
             for highlight in highlightRanges {
+                // Does not work:
+//                textView.textLayoutManager.setRenderingAttributes(attributeProvider.attributesFor(highlight.capture),
+//                                                                  for: NSTextRange(highlight.range,
+//                                                                       provider: textView.textContentStorage)!)
+                // Temp solution (until Apple fixes above)
                 textView.textContentStorage.textStorage?.setAttributes(
                     attributeProvider.attributesFor(highlight.capture),
                     range: highlight.range
@@ -219,7 +227,7 @@ private extension Highlighter {
 private extension Highlighter {
     /// Updates the view to highlight newly visible text when the textview is scrolled or bounds change.
     @objc func visibleTextChanged(_ notification: Notification) {
-        visibleSet = IndexSet(integersIn: Range(textView.visibleTextRange)!)
+        visibleSet = IndexSet(integersIn: Range(textView.visibleTextRange ?? NSRange())!)
 
         // Any indices that are both *not* valid and in the visible text range should be invalidated
         let newlyInvalidSet = visibleSet.subtracting(validSet)