Improve Drag and Drop

Example/CodeEditTextViewExample/CodeEditTextViewExample/Documents/CodeEditTextViewExampleDocument.swift

@@ -25,7 +25,7 @@ struct CodeEditTextViewExampleDocument: FileDocument {
         guard let data = configuration.file.regularFileContents else {
             throw CocoaError(.fileReadCorruptFile)
         }
-        text = String(bytes: data, encoding: .utf8)
+        text = String(bytes: data, encoding: .utf8) ?? ""
     }
 
     func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {

Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager+Public.swift

@@ -8,6 +8,8 @@
 import AppKit
 
 extension TextLayoutManager {
+    // MARK: - Estimate
+
     public func estimatedHeight() -> CGFloat {
         max(lineStorage.height, estimateLineHeight())
     }
@@ -16,6 +18,8 @@ extension TextLayoutManager {
         maxLineWidth + edgeInsets.horizontal
     }
 
+    // MARK: - Text Lines
+
     /// Finds a text line for the given y position relative to the text view.
     ///
     /// Y values begin at the top of the view and extend down. Eg, a `0` y value would  return the first line in
@@ -101,6 +105,8 @@ extension TextLayoutManager {
         }
     }
 
+    // MARK: - Rect For Offset
+
     /// Find a position for the character at a given offset.
     /// Returns the rect of the character at the given offset.
     /// The rect may represent more than one unicode unit, for instance if the offset is at the beginning of an
@@ -263,6 +269,8 @@ extension TextLayoutManager {
         return nil
     }
 
+    // MARK: - Ensure Layout
+
     /// Forces layout calculation for all lines up to and including the given offset.
     /// - Parameter offset: The offset to ensure layout until.
     public func ensureLayoutUntil(_ offset: Int) {

Sources/CodeEditTextView/TextLayoutManager/TextLayoutManger+ensureLayout.swift → Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager+ensureLayout.swift

@@ -1,5 +1,5 @@
 //
-//  TextLayoutManger+ensureLayout.swift
+//  TextLayoutManager+ensureLayout.swift
 //  CodeEditTextView
 //
 //  Created by Khan Winter on 4/7/25.

Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager.swift

@@ -70,7 +70,7 @@ public class TextLayoutManager: NSObject {
     weak var textStorage: NSTextStorage?
     var lineStorage: TextLineStorage<TextLine> = TextLineStorage()
     var markedTextManager: MarkedTextManager = MarkedTextManager()
-    private let viewReuseQueue: ViewReuseQueue<LineFragmentView, UUID> = ViewReuseQueue()
+    let viewReuseQueue: ViewReuseQueue<LineFragmentView, UUID> = ViewReuseQueue()
     package var visibleLineIds: Set<TextLine.ID> = []
     /// Used to force a complete re-layout using `setNeedsLayout`
     package var needsLayout: Bool = false

Sources/CodeEditTextView/TextLine/LineFragment.swift

@@ -6,6 +6,7 @@
 //
 
 import AppKit
+import CodeEditTextViewObjC
 
 /// A ``LineFragment`` represents a subrange of characters in a line. Every text line contains at least one line
 /// fragments, and any lines that need to be broken due to width constraints will contain more than one fragment.
@@ -40,6 +41,43 @@ public final class LineFragment: Identifiable, Equatable {
         lhs.id == rhs.id
     }
 
+    /// Finds the x position of the offset in the string the fragment represents.
+    /// - Parameter offset: The offset, relative to the start of the *line*.
+    /// - Returns: The x position of the character in the drawn line, from the left.
+    public func xPos(for offset: Int) -> CGFloat {
+        return CTLineGetOffsetForStringIndex(ctLine, offset, nil)
+    }
+
+    public func draw(in context: CGContext, yPos: CGFloat) {
+        context.saveGState()
+
+        // Removes jagged edges
+        context.setAllowsAntialiasing(true)
+        context.setShouldAntialias(true)
+
+        // Effectively increases the screen resolution by drawing text in each LED color pixel (R, G, or B), rather than
+        // the triplet of pixels (RGB) for a regular pixel. This can increase text clarity, but loses effectiveness
+        // in low-contrast settings.
+        context.setAllowsFontSubpixelPositioning(true)
+        context.setShouldSubpixelPositionFonts(true)
+
+        // Quantizes the position of each glyph, resulting in slightly less accurate positioning, and gaining higher
+        // quality bitmaps and performance.
+        context.setAllowsFontSubpixelQuantization(true)
+        context.setShouldSubpixelQuantizeFonts(true)
+
+        ContextSetHiddenSmoothingStyle(context, 16)
+
+        context.textMatrix = .init(scaleX: 1, y: -1)
+        context.textPosition = CGPoint(
+            x: 0,
+            y: yPos + height - descent + (heightDifference/2)
+        ).pixelAligned
+
+        CTLineDraw(ctLine, context)
+        context.restoreGState()
+    }
+
     /// Calculates the drawing rect for a given range.
     /// - Parameter range: The range to calculate the bounds for, relative to the line.
     /// - Returns: A rect that contains the text contents in the given range.

Sources/CodeEditTextView/TextLine/LineFragmentView.swift

@@ -6,7 +6,6 @@
 //
 
 import AppKit
-import CodeEditTextViewObjC
 
 /// Displays a line fragment.
 final class LineFragmentView: NSView {
@@ -40,32 +39,6 @@ final class LineFragmentView: NSView {
         guard let lineFragment, let context = NSGraphicsContext.current?.cgContext else {
             return
         }
-        context.saveGState()
-
-        // Removes jagged edges
-        context.setAllowsAntialiasing(true)
-        context.setShouldAntialias(true)
-
-        // Effectively increases the screen resolution by drawing text in each LED color pixel (R, G, or B), rather than
-        // the triplet of pixels (RGB) for a regular pixel. This can increase text clarity, but loses effectiveness
-        // in low-contrast settings.
-        context.setAllowsFontSubpixelPositioning(true)
-        context.setShouldSubpixelPositionFonts(true)
-
-        // Quantizes the position of each glyph, resulting in slightly less accurate positioning, and gaining higher
-        // quality bitmaps and performance.
-        context.setAllowsFontSubpixelQuantization(true)
-        context.setShouldSubpixelQuantizeFonts(true)
-
-        ContextSetHiddenSmoothingStyle(context, 16)
-
-        context.textMatrix = .init(scaleX: 1, y: -1)
-        context.textPosition = CGPoint(
-            x: 0,
-            y: lineFragment.height - lineFragment.descent + (lineFragment.heightDifference/2)
-        ).pixelAligned
-
-        CTLineDraw(lineFragment.ctLine, context)
-        context.restoreGState()
+        lineFragment.draw(in: context, yPos: 0.0)
     }
 }

Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager.swift

@@ -139,17 +139,19 @@ public class TextSelectionManager: NSObject {
 
         for textSelection in textSelections {
             if textSelection.range.isEmpty {
-                let cursorOrigin = (layoutManager?.rectForOffset(textSelection.range.location) ?? .zero).origin
+                guard let cursorRect = layoutManager?.rectForOffset(textSelection.range.location) else {
+                    continue
+                }
 
                 var doesViewNeedReposition: Bool
 
                 // If using the system cursor, macOS will change the origin and height by about 0.5, so we do an
                 // approximate equals in that case to avoid extra updates.
                 if useSystemCursor, #available(macOS 14.0, *) {
-                    doesViewNeedReposition = !textSelection.boundingRect.origin.approxEqual(cursorOrigin)
+                    doesViewNeedReposition = !textSelection.boundingRect.origin.approxEqual(cursorRect.origin)
                     || !textSelection.boundingRect.height.approxEqual(layoutManager?.estimateLineHeight() ?? 0)
                 } else {
-                    doesViewNeedReposition = textSelection.boundingRect.origin != cursorOrigin
+                    doesViewNeedReposition = textSelection.boundingRect.origin != cursorRect.origin
                     || textSelection.boundingRect.height != layoutManager?.estimateLineHeight() ?? 0
                 }
 
@@ -175,8 +177,8 @@ public class TextSelectionManager: NSObject {
                         textView?.addSubview(cursorView)
                     }
 
-                    cursorView.frame.origin = cursorOrigin
-                    cursorView.frame.size.height = heightForCursorAt(textSelection.range) ?? 0
+                    cursorView.frame.origin = cursorRect.origin
+                    cursorView.frame.size.height = cursorRect.height
 
                     textSelection.view = cursorView
                     textSelection.boundingRect = cursorView.frame

Sources/CodeEditTextView/TextView/DraggingTextRenderer.swift

@@ -0,0 +1,109 @@
+//
+//  DraggingTextRenderer.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 11/24/24.
+//
+
+import AppKit
+
+class DraggingTextRenderer: NSView {
+    let ranges: [NSRange]
+    let layoutManager: TextLayoutManager
+
+    override var isFlipped: Bool {
+        true
+    }
+
+    override var intrinsicContentSize: NSSize {
+        self.frame.size
+    }
+
+    init?(ranges: [NSRange], layoutManager: TextLayoutManager) {
+        self.ranges = ranges
+        self.layoutManager = layoutManager
+
+        assert(!ranges.isEmpty, "Empty ranges not allowed")
+
+        var minY: CGFloat = .infinity
+        var maxY: CGFloat = 0.0
+
+        for range in ranges {
+            for line in layoutManager.lineStorage.linesInRange(range) {
+                minY = min(minY, line.yPos)
+                maxY = max(maxY, line.yPos + line.height)
+            }
+        }
+
+        let frame = CGRect(
+            x: layoutManager.edgeInsets.left,
+            y: minY,
+            width: layoutManager.maxLineWidth,
+            height: maxY - minY
+        )
+
+        super.init(frame: frame)
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    override func draw(_ dirtyRect: NSRect) {
+        super.draw(dirtyRect)
+        guard let context = NSGraphicsContext.current?.cgContext,
+              let firstRange = ranges.first,
+              let minRect = layoutManager.rectForOffset(firstRange.lowerBound) else {
+            return
+        }
+
+        for range in ranges {
+            for line in layoutManager.lineStorage.linesInRange(range) {
+                drawLine(line, in: range, yOffset: minRect.minY, context: context)
+            }
+        }
+    }
+
+    private func drawLine(
+        _ line: TextLineStorage<TextLine>.TextLinePosition,
+        in selectedRange: NSRange,
+        yOffset: CGFloat,
+        context: CGContext
+    ) {
+        for fragment in line.data.lineFragments {
+            guard let fragmentRange = fragment.range.shifted(by: line.range.location),
+                  fragmentRange.intersection(selectedRange) != nil else {
+                continue
+            }
+            let fragmentYPos = line.yPos + fragment.yPos - yOffset
+            fragment.data.draw(in: context, yPos: fragmentYPos)
+
+            // Clear text that's not selected
+            if fragmentRange.contains(selectedRange.lowerBound) {
+                let relativeOffset = selectedRange.lowerBound - line.range.lowerBound
+                let selectionXPos = fragment.data.xPos(for: relativeOffset)
+                context.clear(
+                    CGRect(
+                        x: 0.0,
+                        y: fragmentYPos,
+                        width: selectionXPos,
+                        height: fragment.height
+                    ).pixelAligned
+                )
+            }
+
+            if fragmentRange.contains(selectedRange.upperBound) {
+                let relativeOffset = selectedRange.upperBound - line.range.lowerBound
+                let selectionXPos = fragment.data.xPos(for: relativeOffset)
+                context.clear(
+                    CGRect(
+                        x: selectionXPos,
+                        y: fragmentYPos,
+                        width: frame.width - selectionXPos,
+                        height: fragment.height
+                    ).pixelAligned
+                )
+            }
+        }
+    }
+}