Make the composer wrap and grow, and surface Launch at Login

Long prompts hit a single-line field before; the composer is now an
NSTextView that wraps and grows up to seven lines, keeps Return as send,
and uses Shift+Return for a newline. Launch at Login already existed in
the menu bar icon's right-click menu, so it is now also a toggle in the
sync panel where it is easier to find.

Sources/Prompt/ComposerView.swift

@@ -0,0 +1,157 @@
+import AppKit
+import SwiftUI
+
+/// A chat-style composer backed by AppKit: wraps long prompts, grows to fit up
+/// to seven lines, then scrolls. Return submits; Shift+Return inserts a
+/// newline. A plain SwiftUI `TextField(axis: .vertical)` cannot keep Return as
+/// "send", which is why this is not one.
+///
+/// Height is driven by the caller: the representable measures the text and
+/// writes the clamped height into `height`, which the caller applies as a
+/// `.frame(height:)`. Driving the frame is what actually resizes a
+/// representable — `intrinsicContentSize` is ignored once SwiftUI offers a
+/// bigger size.
+struct ComposerView: NSViewRepresentable {
+    @Binding var text: String
+    @Binding var isFocused: Bool
+    @Binding var height: CGFloat
+    var placeholder: String
+    var onSubmit: () -> Void
+    var onEscape: (() -> Void)? = nil
+
+    private let maxLines: CGFloat = 7
+
+    /// The one-line height, so the composer starts at exactly one line instead
+    /// of snapping to its real height on the first keystroke.
+    static var oneLineHeight: CGFloat {
+        let font = NSFont.systemFont(ofSize: NSFont.systemFontSize)
+        return font.ascender - font.descender + font.leading + 10 // 2 x 5 inset
+    }
+
+    func makeCoordinator() -> Coordinator { Coordinator(self) }
+
+    func makeNSView(context: Context) -> NSScrollView {
+        let scrollView = NSScrollView()
+        scrollView.drawsBackground = false
+        scrollView.borderType = .noBorder
+        scrollView.hasVerticalScroller = true
+        scrollView.autohidesScrollers = true
+        scrollView.horizontalScrollElasticity = .none
+
+        let textView = ComposerTextView()
+        textView.delegate = context.coordinator
+        textView.placeholderText = placeholder
+        textView.isRichText = false
+        textView.isVerticallyResizable = true
+        textView.isHorizontallyResizable = false
+        textView.autoresizingMask = [.width]
+        textView.textContainer?.widthTracksTextView = true
+        textView.textContainer?.lineFragmentPadding = 0
+        textView.textContainerInset = NSSize(width: 0, height: 5)
+        textView.font = .systemFont(ofSize: NSFont.systemFontSize)
+        textView.textColor = .labelColor
+        textView.drawsBackground = false
+        // No containerSize: with widthTracksTextView the container follows the
+        // view's width, which is what makes long lines wrap.
+
+        scrollView.documentView = textView
+        textView.frame = NSRect(origin: .zero, size: scrollView.contentSize)
+        context.coordinator.watchWindow(of: textView)
+        return scrollView
+    }
+
+    func updateNSView(_ scrollView: NSScrollView, context: Context) {
+        guard let textView = scrollView.documentView as? ComposerTextView else { return }
+        context.coordinator.parent = self
+        if textView.string != text {
+            textView.string = text
+            updateHeight(textView)
+        }
+        textView.placeholderText = placeholder
+        if isFocused, scrollView.window?.firstResponder != textView {
+            scrollView.window?.makeFirstResponder(textView)
+        }
+    }
+
+    fileprivate func updateHeight(_ textView: ComposerTextView) {
+        guard let layoutManager = textView.layoutManager,
+              let textContainer = textView.textContainer else { return }
+        layoutManager.ensureLayout(for: textContainer)
+        let content = layoutManager.usedRect(for: textContainer).height + 2 * textView.textContainerInset.height
+        let line = Self.oneLineHeight
+        let clamped = max(line, min(content, line * maxLines + 1))
+        if abs(height - clamped) > 0.5 {
+            // Defer so the binding is not written from inside a layout pass.
+            DispatchQueue.main.async { self.height = clamped }
+        }
+    }
+
+    final class Coordinator: NSObject, NSTextViewDelegate {
+        var parent: ComposerView
+        private var windowObserver: Any?
+
+        init(_ parent: ComposerView) { self.parent = parent }
+
+        /// Re-assert focus every time the panel becomes key again. The focus
+        /// binding stays `true` while hidden, so without this a re-shown panel
+        /// would not refocus the composer.
+        fileprivate func watchWindow(of textView: ComposerTextView) {
+            windowObserver = NotificationCenter.default.addObserver(
+                forName: NSWindow.didBecomeKeyNotification, object: nil, queue: .main
+            ) { [weak self, weak textView] note in
+                guard let self, let textView,
+                      (note.object as? NSWindow) === textView.window,
+                      self.parent.isFocused else { return }
+                textView.window?.makeFirstResponder(textView)
+            }
+        }
+
+        deinit {
+            if let windowObserver {
+                NotificationCenter.default.removeObserver(windowObserver)
+            }
+        }
+
+        func textDidChange(_ notification: Notification) {
+            guard let textView = notification.object as? ComposerTextView else { return }
+            if parent.text != textView.string {
+                parent.text = textView.string
+            }
+            parent.updateHeight(textView)
+        }
+
+        // Return sends, Shift+Return inserts a newline. Esc is forwarded so the
+        // panel can clear its selection or hide, which a TextField used to do
+        // via onExitCommand.
+        func textView(_ textView: NSTextView, doCommandBy commandSelector: Selector) -> Bool {
+            if commandSelector == #selector(NSResponder.cancelOperation(_:)) {
+                parent.onEscape?()
+                return true
+            }
+            guard commandSelector == #selector(NSResponder.insertNewline(_:)) else { return false }
+            if NSApp.currentEvent?.modifierFlags.contains(.shift) == true {
+                return false
+            }
+            parent.onSubmit()
+            return true
+        }
+    }
+}
+
+private final class ComposerTextView: NSTextView {
+    var placeholderText: String = "" {
+        didSet { needsDisplay = true }
+    }
+
+    override func draw(_ dirtyRect: NSRect) {
+        super.draw(dirtyRect)
+        guard string.isEmpty, !placeholderText.isEmpty else { return }
+        let attributes: [NSAttributedString.Key: Any] = [
+            .font: font as Any,
+            .foregroundColor: NSColor.placeholderTextColor,
+        ]
+        let inset = textContainerInset
+        let origin = NSPoint(x: inset.width + (textContainer?.lineFragmentPadding ?? 0), y: inset.height)
+        placeholderText.draw(at: origin, withAttributes: attributes)
+    }
+}