Column Selection (#107)

### Description

Adds column selection when pressing option and dragging to select.

### Related Issues

* #46

### 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

Demo, ignore the multiple undos at the end a fix for that is on it's way.

https://github.com/user-attachments/assets/409aa49c-eed2-465f-a964-162920c8877d

Author: thecoolwinter

Sources/CodeEditTextView/TextLayoutManager/TextLayoutManager+Public.swift

@@ -75,14 +75,22 @@ extension TextLayoutManager {
               ) else {
             return nil
         }
-        let fragment = fragmentPosition.data
 
+        return textOffsetAtPoint(point, fragmentPosition: fragmentPosition, linePosition: linePosition)
+    }
+
+    func textOffsetAtPoint(
+        _ point: CGPoint,
+        fragmentPosition: TextLineStorage<LineFragment>.TextLinePosition,
+        linePosition: TextLineStorage<TextLine>.TextLinePosition
+    ) -> Int? {
+        let fragment = fragmentPosition.data
         if fragment.width == 0 {
             return linePosition.range.location + fragmentPosition.range.location
         } else if fragment.width <= point.x - edgeInsets.left {
             return findOffsetAfterEndOf(fragmentPosition: fragmentPosition, in: linePosition)
         } else {
-            return findOffsetAtPoint(inFragment: fragment, point: point, inLine: linePosition)
+            return findOffsetAtPoint(inFragment: fragment, xPos: point.x, inLine: linePosition)
         }
     }
 
@@ -125,23 +133,23 @@ extension TextLayoutManager {
     /// Finds a document offset for a point that lies in a line fragment.
     /// - Parameters:
     ///   - fragment: The fragment the point lies in.
-    ///   - point: The point being queried, relative to the text view.
+    ///   - xPos: The point being queried, relative to the text view.
     ///   - linePosition: The position that contains the `fragment`.
     /// - Returns: The offset (relative to the document) that's closest to the given point, or `nil` if it could not be
     ///            found.
-    private func findOffsetAtPoint(
+    func findOffsetAtPoint(
         inFragment fragment: LineFragment,
-        point: CGPoint,
+        xPos: CGFloat,
         inLine linePosition: TextLineStorage<TextLine>.TextLinePosition
     ) -> Int? {
-        guard let (content, contentPosition) = fragment.findContent(atX: point.x - edgeInsets.left) else {
+        guard let (content, contentPosition) = fragment.findContent(atX: xPos - edgeInsets.left) else {
             return nil
         }
         switch content.data {
         case .text(let ctLine):
             let fragmentIndex = CTLineGetStringIndexForPosition(
                 ctLine,
-                CGPoint(x: point.x - edgeInsets.left - contentPosition.xPos, y: fragment.height/2)
+                CGPoint(x: xPos - edgeInsets.left - contentPosition.xPos, y: fragment.height/2)
             )
             return fragmentIndex + contentPosition.offset + linePosition.range.location
         case .attachment:

Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager.swift

@@ -95,6 +95,7 @@ public class TextSelectionManager: NSObject {
                 (0...(textStorage?.length ?? 0)).contains($0.location)
                 && (0...(textStorage?.length ?? 0)).contains($0.max)
             }
+            .sorted(by: { $0.location < $1.location })
             .map {
                 let selection = TextSelection(range: $0)
                 selection.suggestedXPos = layoutManager?.rectForOffset($0.location)?.minX
@@ -127,6 +128,7 @@ public class TextSelectionManager: NSObject {
         }
         if !didHandle {
             textSelections.append(newTextSelection)
+            textSelections.sort(by: { $0.range.location < $1.range.location })
         }
 
         updateSelectionViews()

Sources/CodeEditTextView/TextView/TextView+ColumnSelection.swift

@@ -0,0 +1,50 @@
+//
+//  TextView+ColumnSelection.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 6/19/25.
+//
+
+import AppKit
+
+extension TextView {
+    /// Set the user's selection to a square region in the editor.
+    ///
+    /// This method will automatically determine a valid region from the provided two points.
+    /// - Parameters:
+    ///   - pointA: The first point.
+    ///   - pointB: The second point.
+    public func selectColumns(betweenPointA pointA: CGPoint, pointB: CGPoint) {
+        let start = CGPoint(x: min(pointA.x, pointB.x), y: min(pointA.y, pointB.y))
+        let end = CGPoint(x: max(pointA.x, pointB.x), y: max(pointA.y, pointB.y))
+
+        // Collect all overlapping text ranges
+        var selectedRanges: [NSRange] = layoutManager.linesStartingAt(start.y, until: end.y).flatMap { textLine in
+            // Collect fragment ranges
+            return textLine.data.lineFragments.compactMap { lineFragment -> NSRange? in
+                let startOffset = self.layoutManager.textOffsetAtPoint(
+                    start,
+                    fragmentPosition: lineFragment,
+                    linePosition: textLine
+                )
+                let endOffset = self.layoutManager.textOffsetAtPoint(
+                    end,
+                    fragmentPosition: lineFragment,
+                    linePosition: textLine
+                )
+                guard let startOffset, let endOffset else { return nil }
+
+                return NSRange(start: startOffset, end: endOffset)
+            }
+        }
+
+        // If we have some non-cursor selections, filter out any cursor selections
+        if selectedRanges.contains(where: { !$0.isEmpty }) {
+            selectedRanges = selectedRanges.filter({
+                !$0.isEmpty || (layoutManager.rectForOffset($0.location)?.origin.x.approxEqual(start.x) ?? false)
+            })
+        }
+
+        selectionManager.setSelectedRanges(selectedRanges)
+    }
+}

Sources/CodeEditTextView/TextView/TextView+FirstResponder.swift

@@ -51,7 +51,10 @@ extension TextView {
     open override func resetCursorRects() {
         super.resetCursorRects()
         if isSelectable {
-            addCursorRect(visibleRect, cursor: .iBeam)
+            addCursorRect(
+                visibleRect,
+                cursor: isOptionPressed ? .crosshair : .iBeam
+            )
         }
     }
 }

Sources/CodeEditTextView/TextView/TextView+KeyDown.swift

@@ -47,4 +47,16 @@ extension TextView {
 
         return false
     }
+
+    override public func flagsChanged(with event: NSEvent) {
+        super.flagsChanged(with: event)
+
+        let modifierFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
+        let modifierFlagsIsOption = modifierFlags == [.option]
+
+        if modifierFlagsIsOption != isOptionPressed {
+            isOptionPressed = modifierFlagsIsOption
+            resetCursorRects()
+        }
+    }
 }

Sources/CodeEditTextView/TextView/TextView+Mouse.swift

@@ -41,10 +41,11 @@ extension TextView {
             super.mouseDown(with: event)
             return
         }
-        if event.modifierFlags.intersection(.deviceIndependentFlagsMask).isSuperset(of: [.control, .shift]) {
+        let eventFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
+        if eventFlags == [.control, .shift] {
             unmarkText()
             selectionManager.addSelectedRange(NSRange(location: offset, length: 0))
-        } else if event.modifierFlags.intersection(.deviceIndependentFlagsMask).contains(.shift) {
+        } else if eventFlags.contains(.shift) {
             unmarkText()
             shiftClickExtendSelection(to: offset)
         } else {
@@ -96,40 +97,11 @@ extension TextView {
                 return
             }
 
-            switch cursorSelectionMode {
-            case .character:
-                selectionManager.setSelectedRange(
-                    NSRange(
-                        location: min(startPosition, endPosition),
-                        length: max(startPosition, endPosition) - min(startPosition, endPosition)
-                    )
-                )
-
-            case .word:
-                let startWordRange = findWordBoundary(at: startPosition)
-                let endWordRange = findWordBoundary(at: endPosition)
-
-                selectionManager.setSelectedRange(
-                    NSRange(
-                        location: min(startWordRange.location, endWordRange.location),
-                        length: max(startWordRange.location + startWordRange.length,
-                                    endWordRange.location + endWordRange.length) -
-                                min(startWordRange.location, endWordRange.location)
-                    )
-                )
-
-            case .line:
-                let startLineRange = findLineBoundary(at: startPosition)
-                let endLineRange = findLineBoundary(at: endPosition)
-
-                selectionManager.setSelectedRange(
-                    NSRange(
-                        location: min(startLineRange.location, endLineRange.location),
-                        length: max(startLineRange.location + startLineRange.length,
-                                    endLineRange.location + endLineRange.length) -
-                                min(startLineRange.location, endLineRange.location)
-                    )
-                )
+            let modifierFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
+            if modifierFlags.contains(.option) {
+                dragColumnSelection(mouseDragAnchor: mouseDragAnchor, event: event)
+            } else {
+                dragSelection(startPosition: startPosition, endPosition: endPosition, mouseDragAnchor: mouseDragAnchor)
             }
 
             setNeedsDisplay()
@@ -164,6 +136,8 @@ extension TextView {
         setNeedsDisplay()
     }
 
+    // MARK: - Mouse Autoscroll
+
     /// Sets up a timer that fires at a predetermined period to autoscroll the text view.
     /// Ensure the timer is disabled using ``disableMouseAutoscrollTimer``.
     func setUpMouseAutoscrollTimer() {
@@ -182,4 +156,50 @@ extension TextView {
         mouseDragTimer?.invalidate()
         mouseDragTimer = nil
     }
+
+    // MARK: - Drag Selection
+
+    private func dragSelection(startPosition: Int, endPosition: Int, mouseDragAnchor: CGPoint) {
+        switch cursorSelectionMode {
+        case .character:
+            selectionManager.setSelectedRange(
+                NSRange(
+                    location: min(startPosition, endPosition),
+                    length: max(startPosition, endPosition) - min(startPosition, endPosition)
+                )
+            )
+
+        case .word:
+            let startWordRange = findWordBoundary(at: startPosition)
+            let endWordRange = findWordBoundary(at: endPosition)
+
+            selectionManager.setSelectedRange(
+                NSRange(
+                    location: min(startWordRange.location, endWordRange.location),
+                    length: max(startWordRange.location + startWordRange.length,
+                                endWordRange.location + endWordRange.length) -
+                    min(startWordRange.location, endWordRange.location)
+                )
+            )
+
+        case .line:
+            let startLineRange = findLineBoundary(at: startPosition)
+            let endLineRange = findLineBoundary(at: endPosition)
+
+            selectionManager.setSelectedRange(
+                NSRange(
+                    location: min(startLineRange.location, endLineRange.location),
+                    length: max(startLineRange.location + startLineRange.length,
+                                endLineRange.location + endLineRange.length) -
+                    min(startLineRange.location, endLineRange.location)
+                )
+            )
+        }
+    }
+
+    private func dragColumnSelection(mouseDragAnchor: CGPoint, event: NSEvent) {
+        // Drag the selection and select in columns
+        let eventLocation = convert(event.locationInWindow, from: nil)
+        selectColumns(betweenPointA: eventLocation, pointB: mouseDragAnchor)
+    }
 }

Sources/CodeEditTextView/TextView/TextView.swift

@@ -269,6 +269,8 @@ public class TextView: NSView, NSTextContent {
     var draggingCursorView: NSView?
     var isDragging: Bool = false
 
+    var isOptionPressed: Bool = false
+
     private var fontCharWidth: CGFloat {
         (" " as NSString).size(withAttributes: [.font: font]).width
     }