Add Parent and Child types for tracking splits; Add methods for

adding start and end children in `Paned` widget;

src/apprt/gtk/Paned.zig

@@ -2,33 +2,40 @@ const Paned = @This();
 
 const std = @import("std");
 const Allocator = std.mem.Allocator;
+const assert = std.debug.assert;
 const font = @import("../../font/main.zig");
 const CoreSurface = @import("../../Surface.zig");
 
 const Window = @import("Window.zig");
 const Surface = @import("Surface.zig");
 const Tab = @import("Tab.zig");
+const Position = @import("parent.zig").Position;
+const Parent = @import("parent.zig").Parent;
 const c = @import("c.zig");
 
 const Child = union(enum) {
     surface: *Surface,
     paned: *Paned,
     empty: void,
+
+    const Self = @This();
+
+    fn is_empty(self: Self) bool {
+        switch (self) {
+            Child.empty => return true,
+            else => return false,
+        }
+    }
 };
 
-const Parent = union(enum) {
-    tab: *Tab,
-    paned: *Paned,
-};
-
-// We'll need to keep a reference to the Window this belongs to for various reasons
-window: *c.GtkWindow,
+/// We'll need to keep a reference to the Window this belongs to for various reasons
+Window: *c.GtkWindow,
 
 // We keep track of the tab label's text so that if a child widget of this pane
 // gets focus (and is a Surface) we can reset the tab label appropriately
 label_text: *c.GtkWidget,
 
-// Our actual GtkPaned widget
+/// Our actual GtkPaned widget
 paned: *c.GtkPaned,
 
 // We have two children, each of which can be either a Surface, another pane,
@@ -96,3 +103,73 @@ pub fn newSurface(self: *Paned, parent_: ?*CoreSurface) !*Surface {
     });
     return surface;
 }
+
+fn addChild1Surface(self: *Paned, surface: *Surface) void {
+    assert(self.child1.is_empty());
+    self.child1 = Child{ .surface = surface };
+    surface.parent = Surface.Parent{ .paned = .{ self, Position.start } };
+    c.gtk_paned_pack1(@ptrCast(self.paned), @ptrCast(surface.gl_area), 1, 0);
+    if (self.child2.is_empty()) {
+        c.gtk_paned_set_position(self.paned, 100);
+    } else {
+        c.gtk_paned_set_position(self.paned, 50);
+    }
+}
+
+fn addChild2Surface(self: *Paned, surface: *Surface) void {
+    assert(self.child1.is_empty());
+    self.child2 = Child{ .surface = surface };
+    surface.parent = Surface.Parent{ .paned = .{ self, Position.end } };
+    c.gtk_paned_pack2(@ptrCast(self.paned), @ptrCast(surface.gl_area), 1, 0);
+    if (self.child2.is_empty()) {
+        c.gtk_paned_set_position(self.paned, 0);
+    } else {
+        c.gtk_paned_set_position(self.paned, 50);
+    }
+}
+
+fn addChild1Paned(self: *Paned, child: *Paned) void {
+    assert(self.child1.is_empty());
+    self.child1 = Child{ .paned = child };
+    child.parent = Parent{ .paned = .{ self, Position.start } };
+    c.gtk_paned_pack1(@ptrCast(self.paned), @ptrCast(child.paned), 1, 0);
+    if (self.child2.is_empty()) {
+        c.gtk_paned_set_position(self.paned, 100);
+    } else {
+        c.gtk_paned_set_position(self.paned, 50);
+    }
+}
+
+fn addChild2Paned(self: *Paned, child: *Paned) void {
+    assert(self.child1.is_empty());
+    self.child2 = Child{ .paned = child };
+    child.parent = Parent{ .paned = .{ self, Position.end } };
+    c.gtk_paned_pack2(@ptrCast(self.paned), @ptrCast(child.paned), 1, 0);
+    if (self.child2.is_empty()) {
+        c.gtk_paned_set_position(self.paned, 0);
+    } else {
+        c.gtk_paned_set_position(self.paned, 50);
+    }
+}
+
+fn removeChild1(self: *Paned) void {
+    assert(!self.child1.is_empty());
+    // todo
+}
+
+fn removeChild2(self: *Paned) void {
+    assert(!self.child1.is_empty());
+    // todo
+}
+
+pub fn splitStartPosition(self: *Paned, orientation: c.GtkOrientation) !void {
+    _ = orientation;
+    _ = self;
+    // todo
+}
+
+pub fn splitEndPosition(self: *Paned, orientation: c.GtkOrientation) !void {
+    _ = orientation;
+    _ = self;
+    // todo
+}

src/apprt/gtk/Surface.zig

@@ -12,8 +12,12 @@ const terminal = @import("../../terminal/main.zig");
 const CoreSurface = @import("../../Surface.zig");
 
 const App = @import("App.zig");
+const Paned = @import("Paned.zig");
+const Tab = @import("Tab.zig");
 const Window = @import("Window.zig");
 const ClipboardConfirmationWindow = @import("ClipboardConfirmationWindow.zig");
+const Position = @import("parent.zig").Position;
+const Parent = @import("parent.zig").Parent;
 const inspector = @import("inspector.zig");
 const gtk_key = @import("key.zig");
 const c = @import("c.zig");
@@ -66,6 +70,9 @@ app: *App,
 /// The window we're part of
 window: *Window,
 
+/// Our parent widget
+parent: Parent,
+
 /// Our GTK area
 gl_area: *c.GtkGLArea,
 
@@ -154,6 +161,7 @@ pub fn init(self: *Surface, app: *App, opts: Options) !void {
     self.* = .{
         .app = app,
         .window = opts.window,
+        .parent = Parent.none,
         .gl_area = opts.gl_area,
         .title = if (opts.title_label) |label| .{
             .label = label,

src/apprt/gtk/Tab.zig

@@ -9,6 +9,10 @@ const Surface = @import("Surface.zig");
 const Window = @import("Window.zig");
 const c = @import("c.zig");
 
+const log = std.log.scoped(.gtk);
+
+const GHOSTTY_TAB = "ghostty_tab";
+
 const Child = union(enum) {
     surface: *Surface,
     paned: *Paned,
@@ -30,7 +34,7 @@ focus_child: *Surface,
 pub fn create(alloc: Allocator, window: *Window, parent_: ?*CoreSurface) !*Tab {
     var tab = try alloc.create(Tab);
     errdefer alloc.destroy(tab);
-    try tab.init(window, _parent);
+    try tab.init(window, parent_);
 }
 
 pub fn init(self: *Tab, window: *Window, parent_: ?*CoreSurface) !void {
@@ -80,7 +84,7 @@ pub fn init(self: *Tab, window: *Window, parent_: ?*CoreSurface) !void {
     const box_widget = c.gtk_box_new(c.GTK_ORIENTATION_VERTICAL, 0);
     c.gtk_widget_set_hexpand(box_widget, 1);
     c.gtk_widget_set_vexpand(box_widget, 1);
-    self.box = ptrCast(box_widget);
+    self.box = @ptrCast(box_widget);
 
     // Initialize the GtkGLArea and attach it to our surface.
     // The surface starts in the "unrealized" state because we have to
@@ -114,7 +118,7 @@ pub fn init(self: *Tab, window: *Window, parent_: ?*CoreSurface) !void {
     }
 
     // Set the userdata of the close button so it points to this page.
-    c.g_object_set_data(@ptrCast(box), GHOSTTY_TAB, self);
+    c.g_object_set_data(@ptrCast(box_widget), GHOSTTY_TAB, self);
 
     // Switch to the new tab
     c.gtk_notebook_set_current_page(self.notebook, page_idx);
@@ -123,3 +127,8 @@ pub fn init(self: *Tab, window: *Window, parent_: ?*CoreSurface) !void {
     // creating a window we want to always focus on the widget.
     _ = c.gtk_widget_grab_focus(box_widget);
 }
+
+fn gtkTabCloseClick(_: *c.GtkButton, ud: ?*anyopaque) callconv(.C) void {
+    _ = ud;
+    // todo
+}

src/apprt/gtk/parent.zig

@@ -0,0 +1,16 @@
+const Paned = @import("Paned.zig");
+const Tab = @import("Tab.zig");
+
+pub const Position = enum {
+    start,
+    end,
+};
+
+pub const Parent = union(enum) {
+    none: void,
+    tab: *Tab,
+    paned: struct {
+        *Paned,
+        Position,
+    },
+};