Add ability to set boot layout.

src/main.zig

@@ -9,6 +9,7 @@ const std = @import("std");
 const adw = @import("adw");
 const gio = @import("gio");
 
+const Settings = @import("Settings.zig");
 const Window = @import("Window.zig");
 const appearance = @import("appearance.zig");
 
@@ -23,6 +24,10 @@ var gpa: std.heap.DebugAllocator(.{}) = .init;
 pub fn main() u8 {
     defer _ = gpa.deinit();
 
+    // Before the allocator's own teardown, since the settings arena comes out
+    // of it. A no-op if the app never got as far as activating.
+    defer Settings.deinit();
+
     // Non-unique so every launch is its own process. The default GApplication
     // behavior hands off to an already-running instance over D-Bus, which for
     // a terminal means a second launch silently does nothing visible here and
@@ -37,6 +42,10 @@ pub fn main() u8 {
 }
 
 fn onActivate(app: *adw.Application, _: ?*anyopaque) callconv(.c) void {
+    // The file both of the next two read from: the scheme, and the tabs the
+    // window opens itself with.
+    Settings.init(gpa.allocator());
+
     // Before the window, so that the first frame is drawn in the scheme the
     // user chose rather than repainted into it a moment later.
     appearance.init();