Disable noncontiguous layout in normal-size documents (close #876)

CHANGELOG.md

@@ -15,6 +15,8 @@ Change Log
 - Improve the performance of text replacement significantly.
 - Improve the line number view fundamentally so that all unwanted behaviors after macOS Mojave disappear.
 - Select the setting selected in the last session when opening the Multiple Replacement window.
+- Enable the noncontiguous layout only with large documents.
+    - This change may improve the editor's dwaring and scrolling behaviors.
 - Improve general performance and stability.
 - [dev] Stop LineNumberView inheriting NSRulerView.
 

CotEditor/Sources/DefaultKeys.swift

@@ -178,6 +178,7 @@ extension DefaultKeys {
     static let enableSmartIndent = DefaultKey<Bool>("enableSmartIndent")
     static let maximumRecentStyleCount = DefaultKey<Int>("maximumRecentStyleCount")
     static let maximumSelectionInstanceHighlightCount = DefaultKey<Int>("maximumSelectionInstanceHighlightCount")
+    static let minimumLengthForNonContiguousLayout = DefaultKey<Int>("minimumLengthForNonContiguousLayout")
     
     static let lastVersion = DefaultKey<String>("lastVersion")
     

CotEditor/Sources/DefaultSettings.swift

@@ -186,6 +186,7 @@ struct DefaultSettings {
         .enableSmartIndent: true,
         .maximumRecentStyleCount: 6,
         .maximumSelectionInstanceHighlightCount: 100,
+        .minimumLengthForNonContiguousLayout: 5_000_000,
         ]
     
     

CotEditor/Sources/EditorTextView.swift

@@ -126,7 +126,6 @@ final class EditorTextView: NSTextView, CurrentLineHighlighting, Themable {
         
         // setup layoutManager and textContainer
         let layoutManager = LayoutManager()
-        layoutManager.allowsNonContiguousLayout = true
         self.textContainer!.replaceLayoutManager(layoutManager)
         
         // set layout values
@@ -297,6 +296,8 @@ final class EditorTextView: NSTextView, CurrentLineHighlighting, Themable {
         
         super.didChangeText()
         
+        self.invalidateNonContiguousLayout()
+        
         self.needsUpdateLineHighlight = true
         
         // retry completion if needed
@@ -805,9 +806,7 @@ final class EditorTextView: NSTextView, CurrentLineHighlighting, Themable {
         super.setLayoutOrientation(orientation)
         self.didChangeValue(forKey: #keyPath(layoutOrientation))
         
-        // enable noncontiguous layout only on normal horizontal layout (2016-06 on OS X 10.11 El Capitan)
-        //  -> Otherwise by vertical layout, the view scrolls occasionally to a strange position on typing.
-        self.layoutManager?.allowsNonContiguousLayout = (orientation == .horizontal)
+        self.invalidateNonContiguousLayout()
         
         // reset writing direction
         if orientation == .vertical {
@@ -1321,6 +1320,19 @@ final class EditorTextView: NSTextView, CurrentLineHighlighting, Themable {
     }
     
     
+    /// validate whether turns the noncontiguous layout on
+    private func invalidateNonContiguousLayout() {
+        
+        let isLargeText = self.string.count > UserDefaults.standard[.minimumLengthForNonContiguousLayout]
+        
+        // enable noncontiguous layout only on normal horizontal layout (2016-06 on OS X 10.11 El Capitan)
+        //  -> Otherwise by vertical layout, the view scrolls occasionally to a strange position on typing.
+        let isHorizontal = (self.layoutOrientation == .horizontal)
+        
+        self.layoutManager?.allowsNonContiguousLayout = isLargeText && isHorizontal
+    }
+    
+    
     /// use legible white-based custom i-beam cursor for dark theme
     private func invalidateCursor() {