Highlight Ignored Indexes (CodeEditApp#114)

# Description

Tracks indexes that were not given an explicit color and highlights them
as normal text. This fixes problems where certain characters would
change color (eg: they were put in a comment) and then need to change
back, but were skipped.

This also fixes the problem in CodeEditApp#99 where text was not given an explicit
highlight on paste. [Since `STTextView` does not add default attributes
to pasted text by
default](https://github.com/krzyzanowskim/STTextView/blob/5d137731401d12412d567244facf086c325ff95b/Sources/STTextView/STTextView%2BCopyPaste.swift#L26)
(see the `useTypingAttributes: false` in that method call).

Doing this also seems to have an effect on the annoying glitching that
was caused when entering text in an empty line (see the comment screen
recording)

This PR also adds a helper for converting from an `NSRange` to a
`Range<Int>` and gets rid of a bunch of ugly force unwraps that existed
before. It also adds some convenience methods for modifying `IndexSet`s
using indexes from `NSRange` objects.

# Related Issues

- CodeEditApp#99 

# UI Fixes

### Paste Text (Old)


https://user-images.githubusercontent.com/35942988/212186310-ee50dcaa-ebec-4e21-905b-562fc2cdf940.mov

### Paste Text (new)


https://user-images.githubusercontent.com/35942988/212186342-402ceb89-2122-4431-88ac-2363e6452323.mov

### Multi-Line comment (old)


https://user-images.githubusercontent.com/35942988/212186411-dc77744f-270b-4615-80c6-ed02e7c38e80.mov

### Multi-Line comment (new)


https://user-images.githubusercontent.com/35942988/212186437-ba014944-fa6c-4de9-8ad3-c8105a655418.mov

Closes CodeEditApp#99

Author: lukepistrol

Sources/CodeEditTextView/Extensions/IndexSet+NSRange.swift

@@ -0,0 +1,38 @@
+//
+//  IndexSet+NSRange.swift
+//  
+//
+//  Created by Khan Winter on 1/12/23.
+//
+
+import Foundation
+
+extension NSRange {
+    /// Convenience getter for safely creating a `Range<Int>` from an `NSRange`
+    var intRange: Range<Int> {
+        self.location..<NSMaxRange(self)
+    }
+}
+
+/// Helpers for working with `NSRange`s and `IndexSet`s.
+extension IndexSet {
+    /// Initializes the  index set with a range of integers
+    init(integersIn range: NSRange) {
+        self.init(integersIn: range.intRange)
+    }
+
+    /// Remove all the integers in the `NSRange`
+    mutating func remove(integersIn range: NSRange) {
+        self.remove(integersIn: range.intRange)
+    }
+
+    /// Insert all the integers in the `NSRange`
+    mutating func insert(integersIn range: NSRange) {
+        self.insert(integersIn: range.intRange)
+    }
+
+    /// Returns true if self contains all of the integers in range.
+    func contains(integersIn range: NSRange) -> Bool {
+        return self.contains(integersIn: range.intRange)
+    }
+}

Sources/CodeEditTextView/Highlighting/Highlighter.swift

@@ -42,10 +42,7 @@ class Highlighter: NSObject {
 
     /// The set of visible indexes in tht text view
     lazy private var visibleSet: IndexSet = {
-        guard let range = textView.visibleTextRange else {
-            return IndexSet()
-        }
-        return IndexSet(integersIn: Range(range)!)
+        return IndexSet(integersIn: textView.visibleTextRange ?? NSRange())
     }()
 
     // MARK: - UI
@@ -107,7 +104,7 @@ class Highlighter: NSObject {
         if !(treeSitterClient?.hasSetText ?? true) {
             treeSitterClient?.setText(text: textView.string)
         }
-        invalidate(range: entireTextRange)
+        invalidate(range: NSRange(entireTextRange))
     }
 
     /// Sets the language and causes a re-highlight of the entire text.
@@ -129,12 +126,6 @@ private extension Highlighter {
     /// Invalidates a given range and adds it to the queue to be highlighted.
     /// - Parameter range: The range to invalidate.
     func invalidate(range: NSRange) {
-        invalidate(range: Range(range)!)
-    }
-
-    /// Invalidates a given range and adds it to the queue to be highlighted.
-    /// - Parameter range: The range to invalidate.
-    func invalidate(range: Range<Int>) {
         let set = IndexSet(integersIn: range)
 
         if set.isEmpty {
@@ -161,31 +152,35 @@ private extension Highlighter {
 
     /// Highlights the given range
     /// - Parameter range: The range to request highlights for.
-    func highlight(range nsRange: NSRange) {
-        let range = Range(nsRange)!
-        pendingSet.insert(integersIn: range)
+    func highlight(range rangeToHighlight: NSRange) {
+        pendingSet.insert(integersIn: rangeToHighlight)
 
-        treeSitterClient?.queryColorsFor(range: nsRange) { [weak self] highlightRanges in
+        treeSitterClient?.queryColorsFor(range: rangeToHighlight) { [weak self] highlightRanges in
             guard let attributeProvider = self?.attributeProvider,
                   let textView = self?.textView else { return }
 
             // Mark these indices as not pending and valid
-            self?.pendingSet.remove(integersIn: range)
-            self?.validSet.formUnion(IndexSet(integersIn: range))
+            self?.pendingSet.remove(integersIn: rangeToHighlight)
+            self?.validSet.formUnion(IndexSet(integersIn: rangeToHighlight))
 
             // If this range does not exist in the visible set, we can exit.
-            if !(self?.visibleSet ?? .init()).contains(integersIn: range) {
+            if !(self?.visibleSet ?? .init()).contains(integersIn: rangeToHighlight) {
                 return
             }
 
             // Try to create a text range for invalidating. If this fails we fail silently
             guard let textContentManager = textView.textLayoutManager.textContentManager,
-                  let textRange = NSTextRange(nsRange, provider: textContentManager) else {
+                  let textRange = NSTextRange(rangeToHighlight, provider: textContentManager) else {
                 return
             }
 
             // Loop through each highlight and modify the textStorage accordingly.
             textView.textContentStorage.textStorage?.beginEditing()
+
+            // Create a set of indexes that were not highlighted.
+            var ignoredIndexes = IndexSet(integersIn: rangeToHighlight)
+
+            // Apply all highlights that need color
             for highlight in highlightRanges {
                 // Does not work:
 //                textView.textLayoutManager.setRenderingAttributes(attributeProvider.attributesFor(highlight.capture),
@@ -196,7 +191,21 @@ private extension Highlighter {
                     attributeProvider.attributesFor(highlight.capture),
                     range: highlight.range
                 )
+
+                // Remove highlighted indexes from the "ignored" indexes.
+                ignoredIndexes.remove(integersIn: highlight.range)
+            }
+
+            // For any indices left over, we need to apply normal attributes to them
+            // This fixes the case where characters are changed to have a non-text color, and then are skipped when
+            // they need to be changed back.
+            for ignoredRange in ignoredIndexes.rangeView {
+                textView.textContentStorage.textStorage?.setAttributes(
+                    attributeProvider.attributesFor(nil),
+                    range: NSRange(ignoredRange)
+                )
             }
+
             textView.textContentStorage.textStorage?.endEditing()
 
             // After applying edits to the text storage we need to invalidate the layout
@@ -227,7 +236,7 @@ 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 ?? NSRange())!)
+        visibleSet = IndexSet(integersIn: textView.visibleTextRange ?? NSRange())
 
         // Any indices that are both *not* valid and in the visible text range should be invalidated
         let newlyInvalidSet = visibleSet.subtracting(validSet)
@@ -263,7 +272,7 @@ extension Highlighter: NSTextStorageDelegate {
         treeSitterClient?.applyEdit(edit,
                                    text: textStorage.string) { [weak self] invalidatedIndexSet in
             let indexSet = invalidatedIndexSet
-                .union(IndexSet(integersIn: Range(editedRange)!))
+                .union(IndexSet(integersIn: editedRange))
                 // Only invalidate indices that aren't visible.
                 .intersection(self?.visibleSet ?? .init())