Set an initial start position (#3929)

Allow the ability to set an initial start position from the config. Adds
`window-initial-position-{x,y}` to the config as an optional i16 value
(see swift docs in [this
comment](https://github.com/ghostty-org/ghostty/pull/3929#discussion_r1899266607)
for the reasoning behind this if needed) and handles setting the
position when the initial window is created

Closes https://github.com/ghostty-org/ghostty/issues/3362

macos/Sources/Features/Terminal/TerminalController.swift

@@ -273,6 +273,28 @@ class TerminalController: BaseTerminalController {
         }
     }
 
+    private func setInitialWindowPosition(x: Int16?, y: Int16?, windowDecorations: Bool) {
+        guard let window else { return }
+
+        // If we don't have both an X and Y we center.
+        guard let x, let y else {
+            window.center()
+            return
+        }
+
+        // Prefer the screen our window is being placed on otherwise our primary screen.
+        guard let screen = window.screen ?? NSScreen.screens.first else {
+            window.center()
+            return
+        }
+
+        // Orient based on the top left of the primary monitor
+        let frame = screen.visibleFrame
+        window.setFrameOrigin(.init(
+            x: frame.minX + CGFloat(x),
+            y: frame.maxY - (CGFloat(y) + window.frame.height)))
+    }
+
     //MARK: - NSWindowController
 
     override func windowWillLoad() {
@@ -368,9 +390,12 @@ class TerminalController: BaseTerminalController {
             }
         }
 
-        // Center the window to start, we'll move the window frame automatically
-        // when cascading.
-        window.center()
+        // Set our window positioning to coordinates if config value exists, otherwise
+        // fallback to original centering behavior
+        setInitialWindowPosition(
+            x: config.windowPositionX,
+            y: config.windowPositionY,
+            windowDecorations: config.windowDecorations)
 
         // Make sure our theme is set on the window so styling is correct.
         if let windowTheme = config.windowTheme {

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -149,6 +149,20 @@ extension Ghostty {
             guard let ptr = v else { return "" }
             return String(cString: ptr)
         }
+        
+        var windowPositionX: Int16? {
+            guard let config = self.config else { return nil }
+            var v: Int16 = 0
+            let key = "window-position-x"
+            return ghostty_config_get(config, &v, key, UInt(key.count)) ? v : nil
+        }
+        
+        var windowPositionY: Int16? {
+            guard let config = self.config else { return nil }
+            var v: Int16 = 0
+            let key = "window-position-y"
+            return ghostty_config_get(config, &v, key, UInt(key.count)) ? v : nil
+        }
 
         var windowNewTabPosition: String {
             guard let config = self.config else { return "" }

src/apprt/glfw.zig

@@ -510,6 +510,13 @@ pub const Surface = struct {
         ) orelse return glfw.mustGetErrorCode();
         errdefer win.destroy();
 
+        // Setup our
+        setInitialWindowPosition(
+            win,
+            app.config.@"window-position-x",
+            app.config.@"window-position-y",
+        );
+
         // Get our physical DPI - debug only because we don't have a use for
         // this but the logging of it may be useful
         if (builtin.mode == .Debug) {
@@ -663,6 +670,17 @@ pub const Surface = struct {
         });
     }
 
+    /// Set the initial window position. This is called exactly once at
+    /// surface initialization time. This may be called before "self"
+    /// is fully initialized.
+    fn setInitialWindowPosition(win: glfw.Window, x: ?i16, y: ?i16) void {
+        const start_position_x = x orelse return;
+        const start_position_y = y orelse return;
+
+        log.debug("setting initial window position ({},{})", .{ start_position_x, start_position_y });
+        win.setPos(.{ .x = start_position_x, .y = start_position_y });
+    }
+
     /// Set the size limits of the window.
     /// Note: this interface is not good, we should redo it if we plan
     /// to use this more. i.e. you can't set max width but no max height,

src/apprt/gtk/App.zig

@@ -786,6 +786,7 @@ fn setInitialSize(
         ),
     }
 }
+
 fn showDesktopNotification(
     self: *App,
     target: apprt.Target,

src/config/Config.zig

@@ -1108,6 +1108,32 @@ keybind: Keybinds = .{},
 @"window-height": u32 = 0,
 @"window-width": u32 = 0,
 
+/// The starting window position. This position is in pixels and is relative
+/// to the top-left corner of the primary monitor. Both values must be set to take
+/// effect. If only one value is set, it is ignored.
+///
+/// Note that the window manager may put limits on the position or override
+/// the position. For example, a tiling window manager may force the window
+/// to be a certain position to fit within the grid. There is nothing Ghostty
+/// will do about this, but it will make an effort.
+///
+/// Also note that negative values are also up to the operating system and
+/// window manager. Some window managers may not allow windows to be placed
+/// off-screen.
+///
+/// Invalid positions are runtime-specific, but generally the positions are
+/// clamped to the nearest valid position.
+///
+/// On macOS, the window position is relative to the top-left corner of
+/// the visible screen area. This means that if the menu bar is visible, the
+/// window will be placed below the menu bar.
+///
+/// Note: this is only supported on macOS and Linux GLFW builds. The GTK
+/// runtime does not support setting the window position (this is a limitation
+/// of GTK 4.0).
+@"window-position-x": ?i16 = null,
+@"window-position-y": ?i16 = null,
+
 /// Whether to enable saving and restoring window state. Window state includes
 /// their position, size, tabs, splits, etc. Some window state requires shell
 /// integration, such as preserving working directories. See `shell-integration`

src/config/c_get.zig

@@ -42,6 +42,11 @@ fn getValue(ptr_raw: *anyopaque, value: anytype) bool {
             ptr.* = @intCast(value);
         },
 
+        i16 => {
+            const ptr: *c_short = @ptrCast(@alignCast(ptr_raw));
+            ptr.* = @intCast(value);
+        },
+
         f32, f64 => |Float| {
             const ptr: *Float = @ptrCast(@alignCast(ptr_raw));
             ptr.* = @floatCast(value);