macos: add selection range to ScreenText

Extend ScreenText to include the active selection's UTF-8 byte offsets
alongside the text and viewport. The selection range is computed as part
of the same formatter pass as the text, so they're guaranteed to be in
sync.

accessibilitySelectedTextRange now reads the cached selection range
directly, and we now return NSNotFound when there's no selection per the
NSAccessibility convention for read-only content.

Author: jparise

include/ghostty.h

@@ -419,6 +419,8 @@ typedef struct {
   uintptr_t text_len;
   uintptr_t viewport_start;
   uintptr_t viewport_end;
+  uintptr_t selection_start;
+  uintptr_t selection_end;
 } ghostty_screen_text_s;
 
 typedef enum {

macos/Sources/Ghostty/Surface View/OSSurfaceView.swift

@@ -49,19 +49,21 @@ extension Ghostty {
         /// True when the surface is in readonly mode.
         @Published private(set) var readonly: Bool = false
 
-        /// Snapshot of the full screen text with viewport position
-        /// and line-start offsets precomputed in UTF-16 space (NSRange
-        /// semantics).
+        /// Snapshot of the full screen text with viewport position,
+        /// optional selection range, and line-start offsets precomputed
+        /// in UTF-16 space (NSRange semantics).
         struct ScreenText: Equatable {
             static let empty = ScreenText(
                 text: "",
                 viewportRange: NSRange(location: 0, length: 0),
+                selectionRange: nil,
                 utf16Length: 0,
                 lineStarts: [0]
             )
 
             let text: String
             let viewportRange: NSRange
+            let selectionRange: NSRange?
             let utf16Length: Int
 
             /// UTF-16 offsets of the start of each line. Always
@@ -252,22 +254,35 @@ extension Ghostty.OSSurfaceView {
 
 extension Ghostty.OSSurfaceView.ScreenText {
     /// Build from a UTF-8 string and the byte offsets that delimit
-    /// the viewport, translating to UTF-16 / NSRange space.
+    /// the viewport and (optionally) the selection, translating to
+    /// UTF-16 / NSRange space. A zero-length selection input means
+    /// "no selection."
     init(
         text: String,
         viewportStartByte: Int,
-        viewportEndByte: Int
+        viewportEndByte: Int,
+        selectionStartByte: Int = 0,
+        selectionEndByte: Int = 0
     ) {
         let utf8 = text.utf8
         let utf16Length = text.utf16.count
 
-        // Convert the viewport from UTF-8 bytes to UTF-16 offsets.
-        let viewportStart = utf8.index(
-            utf8.startIndex, offsetBy: viewportStartByte, limitedBy: utf8.endIndex
-        )?.utf16Offset(in: text) ?? utf16Length
-        let viewportEnd = max(viewportStart, utf8.index(
-            utf8.startIndex, offsetBy: viewportEndByte, limitedBy: utf8.endIndex
-        )?.utf16Offset(in: text) ?? utf16Length)
+        // Convert a UTF-8 byte range from the Zig side to a UTF-16
+        // NSRange, clamping out-of-range offsets to end-of-text.
+        func range(from startByte: Int, to endByte: Int) -> NSRange {
+            let start = utf8.index(
+                utf8.startIndex, offsetBy: startByte, limitedBy: utf8.endIndex
+            )?.utf16Offset(in: text) ?? utf16Length
+            let end = max(start, utf8.index(
+                utf8.startIndex, offsetBy: endByte, limitedBy: utf8.endIndex
+            )?.utf16Offset(in: text) ?? utf16Length)
+            return NSRange(location: start, length: end - start)
+        }
+
+        let viewportRange = range(from: viewportStartByte, to: viewportEndByte)
+        let selectionRange: NSRange? = selectionStartByte < selectionEndByte
+            ? range(from: selectionStartByte, to: selectionEndByte)
+            : nil
 
         // getLineStart's contentsEnd tells us whether the line ended
         // with a terminator — including at end-of-buffer, where a
@@ -294,9 +309,8 @@ extension Ghostty.OSSurfaceView.ScreenText {
 
         self.init(
             text: text,
-            viewportRange: NSRange(
-                location: viewportStart,
-                length: viewportEnd - viewportStart),
+            viewportRange: viewportRange,
+            selectionRange: selectionRange,
             utf16Length: utf16Length,
             lineStarts: lineStarts
         )

macos/Sources/Ghostty/Surface View/SurfaceView_AppKit.swift

@@ -295,7 +295,9 @@ extension Ghostty {
                 return .init(
                     text: String(cString: cString),
                     viewportStartByte: Int(info.viewport_start),
-                    viewportEndByte: Int(info.viewport_end)
+                    viewportEndByte: Int(info.viewport_end),
+                    selectionStartByte: Int(info.selection_start),
+                    selectionEndByte: Int(info.selection_end)
                 )
             }
 
@@ -2307,38 +2309,8 @@ extension Ghostty.SurfaceView {
         return cachedScreenText.get().text
     }
 
-    /// UTF-16 NSRange of the current selection within the cached
-    /// screen text, or `NSRange(NSNotFound, 0)` when no selection
-    /// exists or the selection text appears more than once.
     override func accessibilitySelectedTextRange() -> NSRange {
-        guard let selected = accessibilitySelectedText(), !selected.isEmpty else {
-            return NSRange(location: 0, length: 0)
-        }
-        return Ghostty.SurfaceView.accessibilityRange(
-            of: selected, in: cachedScreenText.get().text)
-    }
-
-    /// UTF-16 NSRange of `needle` inside `haystack` when there is
-    /// exactly one occurrence. Returns `NSRange(NSNotFound, 0)` for
-    /// no match or a multiple-occurrence ambiguous match.
-    static func accessibilityRange(of needle: String, in haystack: String) -> NSRange {
-        guard !needle.isEmpty else { return NSRange(location: NSNotFound, length: 0) }
-        let string = haystack as NSString
-        let first = string.range(of: needle)
-        guard first.location != NSNotFound else {
-            return NSRange(location: NSNotFound, length: 0)
-        }
-        let searchStart = first.location + first.length
-        let rest = NSRange(
-            location: searchStart,
-            length: string.length - searchStart)
-        if rest.length > 0 {
-            let second = string.range(of: needle, range: rest)
-            if second.location != NSNotFound {
-                return NSRange(location: NSNotFound, length: 0)
-            }
-        }
-        return first
+        return cachedScreenText.get().selectionRange ?? NSRange(location: NSNotFound, length: 0)
     }
 
     /// Returns the currently selected text as a string.

macos/Tests/Ghostty/Surface View/OSSurfaceView+ScreenTextTests.swift

@@ -3,8 +3,10 @@ import Foundation
 import Testing
 
 struct OSSurfaceViewScreenTextTests {
+    typealias ScreenText = Ghostty.OSSurfaceView.ScreenText
+
     @Test func emptyTextProducesEmpty() {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "",
             viewportStartByte: 0,
             viewportEndByte: 0
@@ -13,7 +15,7 @@ struct OSSurfaceViewScreenTextTests {
     }
 
     @Test func asciiOffsetsAreIdentity() {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "hello\nworld",
             viewportStartByte: 6,
             viewportEndByte: 11
@@ -26,7 +28,7 @@ struct OSSurfaceViewScreenTextTests {
         // U+1F600 ("😀") is 4 bytes in UTF-8 and a surrogate pair (two
         // code units) in UTF-16.
         let text = "a😀b"
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: text,
             viewportStartByte: 0,
             viewportEndByte: text.utf8.count
@@ -38,7 +40,7 @@ struct OSSurfaceViewScreenTextTests {
 
     @Test func viewportRangeSkipsAcrossSurrogatePair() {
         let text = "a😀b"
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: text,
             viewportStartByte: 5,  // byte index of "b"
             viewportEndByte: 6     // byte index past "b"
@@ -48,7 +50,7 @@ struct OSSurfaceViewScreenTextTests {
 
     @Test func cjkCharacterCountsAsOneUTF16Unit() {
         let text = "好"
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: text,
             viewportStartByte: 0,
             viewportEndByte: text.utf8.count
@@ -58,7 +60,7 @@ struct OSSurfaceViewScreenTextTests {
     }
 
     @Test func viewportPastEndClampsToEndOfText() {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "hi",
             viewportStartByte: 10,
             viewportEndByte: 20
@@ -70,7 +72,7 @@ struct OSSurfaceViewScreenTextTests {
     @Test func reversedOffsetsCollapseToZeroLength() {
         // A negative NSRange.length is meaningless to AX clients; the
         // init normalizes to a zero-length range at start.
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "abcdef",
             viewportStartByte: 4,
             viewportEndByte: 2
@@ -85,7 +87,7 @@ struct OSSurfaceViewScreenTextTests {
             from: text.utf8.startIndex,
             to: text.range(of: viewport)!.lowerBound.samePosition(in: text.utf8)!
         )
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: text,
             viewportStartByte: start,
             viewportEndByte: start + viewport.utf8.count
@@ -107,7 +109,7 @@ struct OSSurfaceViewScreenTextTests {
         ("a\nb\n", [0, 2, 4]),
     ])
     func lineStarts(text: String, expected: [Int]) {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: text, viewportStartByte: 0, viewportEndByte: text.utf8.count
         )
         #expect(screenText.lineStarts == expected)
@@ -123,14 +125,14 @@ struct OSSurfaceViewScreenTextTests {
         (100, 2) // way past end still clamps
     ])
     func lineAtIndex(index: Int, expected: Int) {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "a\nb\nc", viewportStartByte: 0, viewportEndByte: 5
         )
         #expect(screenText.line(at: index) == expected)
     }
 
     @Test func lineAtNegativeIndexClampsToZero() {
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "a\nb", viewportStartByte: 0, viewportEndByte: 3
         )
         #expect(screenText.line(at: -1) == 0)
@@ -139,9 +141,53 @@ struct OSSurfaceViewScreenTextTests {
     @Test func lineForEmptyText() {
         // Past-end indices clamp to line 0 when the text is empty;
         // the in-range `at: 0` case is covered by lineAtIndex.
-        let screenText = Ghostty.OSSurfaceView.ScreenText(
+        let screenText = ScreenText(
             text: "", viewportStartByte: 0, viewportEndByte: 0
         )
         #expect(screenText.line(at: 100) == 0)
     }
+
+    // MARK: selectionRange
+
+    @Test(arguments: [
+        (2, 2),  // zero-length (also the default-args case)
+        (4, 2),  // reversed
+    ])
+    func selectionMustBePositive(startByte: Int, endByte: Int) {
+        let screenText = ScreenText(
+            text: "hello",
+            viewportStartByte: 0, viewportEndByte: 5,
+            selectionStartByte: startByte, selectionEndByte: endByte
+        )
+        #expect(screenText.selectionRange == nil)
+    }
+
+    @Test func selectionAsciiOffsetsAreIdentity() {
+        let screenText = ScreenText(
+            text: "hello world",
+            viewportStartByte: 0, viewportEndByte: 11,
+            selectionStartByte: 6, selectionEndByte: 11
+        )
+        #expect(screenText.selectionRange == NSRange(location: 6, length: 5))
+    }
+
+    @Test func selectionAcrossSurrogatePair() {
+        let text = "a😀b"
+        let screenText = ScreenText(
+            text: text,
+            viewportStartByte: 0, viewportEndByte: text.utf8.count,
+            selectionStartByte: 1, selectionEndByte: 5  // "😀"
+        )
+        // "😀" occupies a UTF-16 surrogate pair (locations 1..3).
+        #expect(screenText.selectionRange == NSRange(location: 1, length: 2))
+    }
+
+    @Test func selectionPastEndClampsToEndOfText() {
+        let screenText = ScreenText(
+            text: "hi",
+            viewportStartByte: 0, viewportEndByte: 2,
+            selectionStartByte: 10, selectionEndByte: 20
+        )
+        #expect(screenText.selectionRange == NSRange(location: 2, length: 0))
+    }
 }

macos/Tests/Ghostty/Surface View/SurfaceView+AccessibilityTests.swift

@@ -1310,6 +1310,8 @@ pub const CAPI = struct {
         text_len: usize,
         viewport_start: usize,
         viewport_end: usize,
+        selection_start: usize,
+        selection_end: usize,
 
         pub fn deinit(self: *ScreenText) void {
             if (self.text) |ptr| {
@@ -1689,10 +1691,11 @@ pub const CAPI = struct {
     }
 
     /// Read the full screen text along with the UTF-8 byte offsets
-    /// that delimit the visible viewport, as a self-consistent
-    /// snapshot. On success free with ghostty_surface_free_screen_text.
-    /// On failure `*result` is zero-initialized so calling
-    /// ghostty_surface_free_screen_text on it is a safe no-op.
+    /// that delimit the visible viewport and (if `has_selection`) the
+    /// active selection, as a self-consistent snapshot. On success
+    /// free with ghostty_surface_free_screen_text. On failure `*result`
+    /// is zero-initialized so calling ghostty_surface_free_screen_text
+    /// on it is a safe no-op.
     export fn ghostty_surface_read_screen(
         surface: *Surface,
         result: *ScreenText,
@@ -1706,6 +1709,8 @@ pub const CAPI = struct {
                 .text_len = 0,
                 .viewport_start = 0,
                 .viewport_end = 0,
+                .selection_start = 0,
+                .selection_end = 0,
             };
             return false;
         };
@@ -1714,6 +1719,8 @@ pub const CAPI = struct {
             .text_len = screen_text.text.len,
             .viewport_start = screen_text.viewport.start,
             .viewport_end = screen_text.viewport.end,
+            .selection_start = if (screen_text.selection) |s| s.start else 0,
+            .selection_end = if (screen_text.selection) |s| s.end else 0,
         };
         return true;
     }