macOS: prevent native window drag by top region when titlebar hidden

The native window drag region is driven ultimately by the window's
`contentLayoutRect`, so we can just override it in `TerminalWindow`
to return a rect the size of the full window, disabling the gesture
without causing any side effects by altering the responder chain.

macos/Sources/Features/Terminal/TerminalController.swift

@@ -22,7 +22,7 @@ class TerminalController: BaseTerminalController {
     private var restorable: Bool = true
 
     /// The configuration derived from the Ghostty config so we don't need to rely on references.
-    private var derivedConfig: DerivedConfig
+    private(set) var derivedConfig: DerivedConfig
 
     /// The notification cancellable for focused surface property changes.
     private var surfaceAppearanceCancellables: Set<AnyCancellable> = []
@@ -318,9 +318,9 @@ class TerminalController: BaseTerminalController {
 
             // Full size content view so we can extend
             // content in to the hidden titlebar's area
-                .fullSizeContentView,
+            .fullSizeContentView,
 
-                .resizable,
+            .resizable,
             .closable,
             .miniaturizable,
         ]
@@ -776,7 +776,7 @@ class TerminalController: BaseTerminalController {
         toggleFullscreen(mode: fullscreenMode)
     }
 
-    private struct DerivedConfig {
+    struct DerivedConfig {
         let backgroundColor: Color
         let macosTitlebarStyle: String
 

macos/Sources/Features/Terminal/TerminalWindow.swift

@@ -115,6 +115,21 @@ class TerminalWindow: NSWindow {
         }
     }
 
+    // We override this so that with the hidden titlebar style the titlebar
+    // area is not draggable.
+    override var contentLayoutRect: CGRect {
+        var rect = super.contentLayoutRect
+
+        // If we are using a hidden titlebar style, the content layout is the
+        // full frame making it so that it is not draggable.
+        if let controller = windowController as? TerminalController,
+              controller.derivedConfig.macosTitlebarStyle == "hidden" {
+            rect.origin.y = 0
+            rect.size.height = self.frame.height
+        }
+        return rect
+    }
+
     // The window theme configuration from Ghostty. This is used to control some
     // behaviors that don't look quite right in certain situations.
     var windowTheme: TerminalWindowTheme?

src/config/Config.zig

@@ -1816,9 +1816,12 @@ keybind: Keybinds = .{},
 /// The "hidden" style hides the titlebar. Unlike `window-decoration = false`,
 /// however, it does not remove the frame from the window or cause it to have
 /// squared corners. Changing to or from this option at run-time may affect
-/// existing windows in buggy ways. The top titlebar area of the window will
-/// continue to drag the window around and you will not be able to use
-/// the mouse for terminal events in this space.
+/// existing windows in buggy ways.
+///
+/// When "hidden", the top titlebar area can no longer be used for dragging
+/// the window. To drag the window, you can use option+click on the resizable
+/// areas of the frame to drag the window. This is a standard macOS behavior
+/// and not something Ghostty enables.
 ///
 /// The default value is "transparent". This is an opinionated choice
 /// but its one I think is the most aesthetically pleasing and works in