From 33b5b69ffec448fcbffc4651308559c31afcb37e Mon Sep 17 00:00:00 2001
From: Christian Tietze <me@christiantietze.de>
Date: Sat, 18 Nov 2023 19:22:54 +0100
Subject: [PATCH] Default attributes (#34)

* apply default text view attributes

* always use stored properties, even with TK2

* opt into TextKit 2 on iOS, too

Circumvents #20

* adjust tests for permanent attributes

* fix pasting code from Xcode rendering oddly

* store defaultTextViewAttributes to fix applying outdated styles
---
 Projects/NeonExample-iOS/ViewController.swift | 11 ++++--
 Projects/NeonExample/ViewController.swift     | 10 ++++--
 Sources/Neon/TextViewSystemInterface.swift    | 35 +++++++++++--------
 .../TextViewSystemInterfaceTests.swift        | 13 +++----
 4 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/Projects/NeonExample-iOS/ViewController.swift b/Projects/NeonExample-iOS/ViewController.swift
index 01ad91a..6d4dbcc 100644
--- a/Projects/NeonExample-iOS/ViewController.swift
+++ b/Projects/NeonExample-iOS/ViewController.swift
@@ -19,17 +19,25 @@ final class ViewController: UIViewController {
 		let boldFont = UIFont.monospacedSystemFont(ofSize: 16, weight: .bold)
 		let italicFont = regularFont.fontDescriptor.withSymbolicTraits(.traitItalic).map { UIFont(descriptor: $0, size: 16) } ?? regularFont
 
+		// Set the default styles. This is applied by stock `NSTextStorage`s during
+		// so-called "attribute fixing" when you type, and we emulate that as
+		// part of the highlighting process in `TextViewSystemInterface`.
+		textView.font = regularFont
+		textView.textColor = .darkGray
+
 		let provider: TextViewSystemInterface.AttributeProvider = { token in
 			return switch token.name {
 			case let keyword where keyword.hasPrefix("keyword"): [.foregroundColor: UIColor.red, .font: boldFont]
 			case "comment": [.foregroundColor: UIColor.green, .font: italicFont]
-			default: [.foregroundColor: UIColor.darkText, .font: regularFont]
+			// Note: Default is not actually applied to unstyled/untokenized text.
+			default: [.foregroundColor: UIColor.blue, .font: regularFont]
 			}
 		}
 
 		return try! TextViewHighlighter(textView: textView,
 										language: language,
 										highlightQuery: query,
+										executionMode: .synchronous,
 										attributeProvider: provider)
 	}()
 
@@ -37,7 +45,6 @@ final class ViewController: UIViewController {
 		super.viewDidLoad()
 
 		_ = highlighter.textView
-		_ = textView.layoutManager
 
 		textView.text = """
 		// Example Code!
diff --git a/Projects/NeonExample/ViewController.swift b/Projects/NeonExample/ViewController.swift
index 8638cf9..42f9278 100644
--- a/Projects/NeonExample/ViewController.swift
+++ b/Projects/NeonExample/ViewController.swift
@@ -10,6 +10,7 @@ final class ViewController: NSViewController {
 
 	init() {
 		self.textView = NSTextView()
+		textView.isRichText = false  // Discards any attributes when pasting.
 
 		scrollView.documentView = textView
 		
@@ -17,15 +18,18 @@ final class ViewController: NSViewController {
 		let boldFont = NSFont.monospacedSystemFont(ofSize: 16, weight: .bold)
 		let italicFont = NSFont(descriptor: regularFont.fontDescriptor.withSymbolicTraits(.italic), size: 16) ?? regularFont
 
-		// Alternatively, set `textView.typingAttributes = [.font: regularFont, ...]`
-		// if you want to customize other default (fallback) attributes.
+		// Set the default styles. This is applied by stock `NSTextStorage`s during
+		// so-called "attribute fixing" when you type, and we emulate that as
+		// part of the highlighting process in `TextViewSystemInterface`.
 		textView.font = regularFont
+		textView.textColor = .darkGray
 
 		let provider: TextViewSystemInterface.AttributeProvider = { token in
 			return switch token.name {
 			case let keyword where keyword.hasPrefix("keyword"): [.foregroundColor: NSColor.red, .font: boldFont]
 			case "comment": [.foregroundColor: NSColor.green, .font: italicFont]
-			default: [.foregroundColor: NSColor.textColor, .font: regularFont]
+			// Note: Default is not actually applied to unstyled/untokenized text.
+			default: [.foregroundColor: NSColor.blue, .font: regularFont]
 			}
 		}
 
diff --git a/Sources/Neon/TextViewSystemInterface.swift b/Sources/Neon/TextViewSystemInterface.swift
index 4bfc309..f11496e 100644
--- a/Sources/Neon/TextViewSystemInterface.swift
+++ b/Sources/Neon/TextViewSystemInterface.swift
@@ -14,9 +14,20 @@ public struct TextViewSystemInterface {
 
 	public let textView: TextView
 	public let attributeProvider: AttributeProvider
+	public var defaultTextViewAttributes: [NSAttributedString.Key: Any] = [:]
 
-	public init(textView: TextView, attributeProvider: @escaping AttributeProvider) {
+	public init(
+		textView: TextView,
+		defaultTextViewAttributes: [NSAttributedString.Key: Any] = [:],
+		attributeProvider: @escaping AttributeProvider
+	) {
 		self.textView = textView
+		// Assume that the default styles used before enabling any highlighting
+		// should be retained, unless client code overrides this.
+		self.defaultTextViewAttributes = [
+			 .font: textView.font as Any,
+			 .foregroundColor: textView.textColor as Any,
+		].merging(defaultTextViewAttributes) { _, override in override }
 		self.attributeProvider = attributeProvider
 	}
 
@@ -43,34 +54,28 @@ public struct TextViewSystemInterface {
 }
 
 extension TextViewSystemInterface: TextSystemInterface {
-	private func setAttributes(_ attrs: [NSAttributedString.Key : Any], in range: NSRange) {
+	private func clamped(range: NSRange) -> NSRange {
 		let endLocation = min(range.max, length)
 
 		assert(endLocation == range.max, "range is out of bounds, is the text state being updated correctly?")
 
-		let clampedRange = NSRange(range.location..<endLocation)
+		return NSRange(range.location..<endLocation)
+	}
 
-		// try text kit 2 first
-		if
-			#available(macOS 12, iOS 15.0, tvOS 15.0, *),
-			let textLayoutManager = textLayoutManager,
-			let contentManager = textLayoutManager.textContentManager,
-			let textRange = NSTextRange(clampedRange, provider: contentManager)
-		{
-			textLayoutManager.setRenderingAttributes(attrs, for: textRange)
-			return
-		}
+	private func setAttributes(_ attrs: [NSAttributedString.Key : Any]?, in range: NSRange) {
+		let clampedRange = clamped(range: range)
 
-		// For TextKit 1: Fall back to applying styles directly to the storage.
+		// Both `NSTextLayoutManager.setRenderingAttributes` and
 		// `NSLayoutManager.setTemporaryAttributes` is limited to attributes
 		// that don't affect layout, like color. So it ignores fonts,
 		// making font weight changes or italicizing text impossible.
 		assert(textStorage != nil, "TextView's NSTextStorage cannot be nil")
+		let attrs = attrs ?? defaultTextViewAttributes
 		textStorage?.setAttributes(attrs, range: clampedRange)
 	}
 
 	public func clearStyle(in range: NSRange) {
-		setAttributes([:], in: range)
+		setAttributes(nil, in: range)
 	}
 
 	public func applyStyle(to token: Token) {
diff --git a/Tests/NeonTests/TextViewSystemInterfaceTests.swift b/Tests/NeonTests/TextViewSystemInterfaceTests.swift
index 7e0d4d7..8628151 100644
--- a/Tests/NeonTests/TextViewSystemInterfaceTests.swift
+++ b/Tests/NeonTests/TextViewSystemInterfaceTests.swift
@@ -65,7 +65,6 @@ final class TextViewSystemInterfaceTests: XCTestCase {
 		XCTAssertEqual(attrs.count, 1)
 		XCTAssertEqual(attrs[.foregroundColor] as? PlatformColor, PlatformColor.red)
 		XCTAssertEqual(effectiveRange, NSRange(0..<6))
-
 	}
 #endif
 
@@ -91,15 +90,13 @@ final class TextViewSystemInterfaceTests: XCTestCase {
 
 		system.applyStyle(to: Token(name: "test", range: NSRange(0..<6)))
 
-		let documentRange = textLayoutManager.documentRange
-
-		var attrRangePairs = [([NSAttributedString.Key: Any], NSTextRange)]()
+		let textStorage = try XCTUnwrap(system.textStorage)
+		let documentRange = NSRange(location: 0, length: textStorage.length)
 
-		textLayoutManager.enumerateRenderingAttributes(from: documentRange.location, reverse: false, using: { _, attrs, range in
+		var attrRangePairs = [([NSAttributedString.Key: Any], NSRange)]()
+		textStorage.enumerateAttributes(in: documentRange) { attrs, range, _ in
 			attrRangePairs.append((attrs, range))
-
-			return true
-		})
+		}
 
 		XCTAssertEqual(attrRangePairs.count, 1)