Smarter Default Highlight Provider Management (#310)

### Description

Updates the highlight provider parameter to correctly reflect its
documentation, and use a smarter method for keeping around the default
highlighter. This fixes an issue where the default highlight provider
was re-initialized on every view update (keyboard navigation,
keystrokes, etc.).

Now, highlight providers have two states: `nil` or `Array`. If CESE sees
a `nil` argument, it creates and keeps around a `TreeSitterClient` like
the documentation says. This client is kept as a variable on the view's
coordinator so it isn't re-initialized between view updates.

This also allows highlighting to be disabled by passing an empty array
for the highlight providers parameter, causing CESE to not make any
default providers.

### Related Issues

* closes #293
* closes #298

### 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

N/A

Author: thecoolwinter

Sources/CodeEditSourceEditor/CodeEditSourceEditor/CodeEditSourceEditor+Coordinator.swift

@@ -18,9 +18,12 @@ extension CodeEditSourceEditor {
         var text: TextAPI
         @Binding var cursorPositions: [CursorPosition]
 
-        init(text: TextAPI, cursorPositions: Binding<[CursorPosition]>) {
+        private(set) var highlightProviders: [any HighlightProviding]
+
+        init(text: TextAPI, cursorPositions: Binding<[CursorPosition]>, highlightProviders: [any HighlightProviding]?) {
             self.text = text
             self._cursorPositions = cursorPositions
+            self.highlightProviders = highlightProviders ?? [TreeSitterClient()]
             super.init()
 
             NotificationCenter.default.addObserver(
@@ -38,6 +41,14 @@ extension CodeEditSourceEditor {
             )
         }
 
+        func updateHighlightProviders(_ highlightProviders: [any HighlightProviding]?) {
+            guard let highlightProviders else {
+                return // Keep our default `TreeSitterClient` if they're `nil`
+            }
+            // Otherwise, we can replace the stored providers.
+            self.highlightProviders = highlightProviders
+        }
+
         @objc func textViewDidChangeText(_ notification: Notification) {
             guard let textView = notification.object as? TextView,
                   let controller,

Sources/CodeEditSourceEditor/CodeEditSourceEditor/CodeEditSourceEditor.swift

@@ -35,8 +35,8 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
     ///   - cursorPositions: The cursor's position in the editor, measured in `(lineNum, columnNum)`
     ///   - useThemeBackground: Determines whether the editor uses the theme's background color, or a transparent
     ///                         background color
-    ///   - highlightProvider: A class you provide to perform syntax highlighting. Leave this as `nil` to use the
-    ///                        built-in `TreeSitterClient` highlighter.
+    ///   - highlightProviders: A set of classes you provide to perform syntax highlighting. Leave this as `nil` to use
+    ///                         the default `TreeSitterClient` highlighter.
     ///   - contentInsets: Insets to use to offset the content in the enclosing scroll view. Leave as `nil` to let the
     ///                    scroll view automatically adjust content insets.
     ///   - additionalTextInsets: An additional amount to inset the text of the editor by.
@@ -62,7 +62,7 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
         editorOverscroll: CGFloat = 0,
         cursorPositions: Binding<[CursorPosition]>,
         useThemeBackground: Bool = true,
-        highlightProviders: [any HighlightProviding] = [TreeSitterClient()],
+        highlightProviders: [any HighlightProviding]? = nil,
         contentInsets: NSEdgeInsets? = nil,
         additionalTextInsets: NSEdgeInsets? = nil,
         isEditable: Bool = true,
@@ -116,8 +116,8 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
     ///   - cursorPositions: The cursor's position in the editor, measured in `(lineNum, columnNum)`
     ///   - useThemeBackground: Determines whether the editor uses the theme's background color, or a transparent
     ///                         background color
-    ///   - highlightProvider: A class you provide to perform syntax highlighting. Leave this as `nil` to use the
-    ///                        built-in `TreeSitterClient` highlighter.
+    ///   - highlightProviders: A set of classes you provide to perform syntax highlighting. Leave this as `nil` to use
+    ///                         the default `TreeSitterClient` highlighter.
     ///   - contentInsets: Insets to use to offset the content in the enclosing scroll view. Leave as `nil` to let the
     ///                    scroll view automatically adjust content insets.
     ///   - isEditable: A Boolean value that controls whether the text view allows the user to edit text.
@@ -141,7 +141,7 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
         editorOverscroll: CGFloat = 0,
         cursorPositions: Binding<[CursorPosition]>,
         useThemeBackground: Bool = true,
-        highlightProviders: [any HighlightProviding] = [TreeSitterClient()],
+        highlightProviders: [any HighlightProviding]? = nil,
         contentInsets: NSEdgeInsets? = nil,
         additionalTextInsets: NSEdgeInsets? = nil,
         isEditable: Bool = true,
@@ -192,7 +192,7 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
     private var editorOverscroll: CGFloat
     package var cursorPositions: Binding<[CursorPosition]>
     private var useThemeBackground: Bool
-    private var highlightProviders: [any HighlightProviding]
+    private var highlightProviders: [any HighlightProviding]?
     private var contentInsets: NSEdgeInsets?
     private var additionalTextInsets: NSEdgeInsets?
     private var isEditable: Bool
@@ -219,7 +219,7 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
             cursorPositions: cursorPositions.wrappedValue,
             editorOverscroll: editorOverscroll,
             useThemeBackground: useThemeBackground,
-            highlightProviders: highlightProviders,
+            highlightProviders: context.coordinator.highlightProviders,
             contentInsets: contentInsets,
             additionalTextInsets: additionalTextInsets,
             isEditable: isEditable,
@@ -249,10 +249,12 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
     }
 
     public func makeCoordinator() -> Coordinator {
-        Coordinator(text: text, cursorPositions: cursorPositions)
+        Coordinator(text: text, cursorPositions: cursorPositions, highlightProviders: highlightProviders)
     }
 
     public func updateNSViewController(_ controller: TextViewController, context: Context) {
+        context.coordinator.updateHighlightProviders(highlightProviders)
+
         if !context.coordinator.isUpdateFromTextView {
             // Prevent infinite loop of update notifications
             context.coordinator.isUpdatingFromRepresentable = true
@@ -267,23 +269,23 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
 
         // Do manual diffing to reduce the amount of reloads.
         // This helps a lot in view performance, as it otherwise gets triggered on each environment change.
-        guard !paramsAreEqual(controller: controller) else {
+        guard !paramsAreEqual(controller: controller, coordinator: context.coordinator) else {
             return
         }
 
-        updateControllerParams(controller: controller)
+        updateControllerParams(controller: controller, coordinator: context.coordinator)
 
         controller.reloadUI()
         return
     }
 
     /// Update the parameters of the controller.
     /// - Parameter controller: The controller to update.
-    func updateControllerParams(controller: TextViewController) {
+    func updateControllerParams(controller: TextViewController, coordinator: Coordinator) {
         updateTextProperties(controller)
         updateEditorProperties(controller)
         updateThemeAndLanguage(controller)
-        updateHighlighting(controller)
+        updateHighlighting(controller, coordinator: coordinator)
     }
 
     private func updateTextProperties(_ controller: TextViewController) {
@@ -336,9 +338,9 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
         }
     }
 
-    private func updateHighlighting(_ controller: TextViewController) {
-        if !areHighlightProvidersEqual(controller: controller) {
-            controller.setHighlightProviders(highlightProviders)
+    private func updateHighlighting(_ controller: TextViewController, coordinator: Coordinator) {
+        if !areHighlightProvidersEqual(controller: controller, coordinator: coordinator) {
+            controller.setHighlightProviders(coordinator.highlightProviders)
         }
 
         if controller.bracketPairEmphasis != bracketPairEmphasis {
@@ -349,7 +351,7 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
     /// Checks if the controller needs updating.
     /// - Parameter controller: The controller to check.
     /// - Returns: True, if the controller's parameters should be updated.
-    func paramsAreEqual(controller: NSViewControllerType) -> Bool {
+    func paramsAreEqual(controller: NSViewControllerType, coordinator: Coordinator) -> Bool {
         controller.font == font &&
         controller.isEditable == isEditable &&
         controller.isSelectable == isSelectable &&
@@ -367,11 +369,12 @@ public struct CodeEditSourceEditor: NSViewControllerRepresentable {
         controller.bracketPairEmphasis == bracketPairEmphasis &&
         controller.useSystemCursor == useSystemCursor &&
         controller.showMinimap == showMinimap &&
-        areHighlightProvidersEqual(controller: controller)
+        areHighlightProvidersEqual(controller: controller, coordinator: coordinator)
     }
 
-    private func areHighlightProvidersEqual(controller: TextViewController) -> Bool {
-        controller.highlightProviders.map { ObjectIdentifier($0) } == highlightProviders.map { ObjectIdentifier($0) }
+    private func areHighlightProvidersEqual(controller: TextViewController, coordinator: Coordinator) -> Bool {
+        controller.highlightProviders.map { ObjectIdentifier($0) }
+        == coordinator.highlightProviders.map { ObjectIdentifier($0) }
     }
 }