Support switching between light and dark themes (#613)

* Support switching between light and dark themes

This uses AdwStyleManager's facilities for specifying whether the light or dark variant of the system theme should be used. If the system doesn't indicate a preference, the default is to use dark.

* Save the color scheme preference to the settings.

CHANGELOG.md

@@ -12,6 +12,7 @@ Thanks to the following contributors who worked on this release:
 ### Added
 - Ported to GTK4 and libadwaita
   - Due to API changes in GTK4, the File -> New Screenshot option now invokes platform-specific tools (the XDG screenshot portal on Linux, and the screenshot tool on maCOS). This is currently unsupported on Windows
+  - Added a preference (in the `View` menu) for switching between a dark or light color scheme.
 - Upgraded to .NET 8
   - Building against .NET 7 is still supported. When building from the tarball, .NET 7 will be used if .NET 8 is unavailable.
 - Restored support for add-ins, which had been disabled in Pinta 2.0 due to technical limitations

Pinta.Core/Actions/ViewActions.cs

@@ -45,6 +45,7 @@ public sealed class ViewActions
 	public ToggleCommand ToolBox { get; }
 	public ToggleCommand Rulers { get; }
 	public Gio.SimpleAction RulerMetric { get; }
+	public Gio.SimpleAction ColorScheme { get; }
 	public Command Fullscreen { get; }
 
 	public ToolBarComboBox ZoomComboBox { get; }
@@ -75,6 +76,7 @@ public ViewActions ()
 		ToolBox = new ToggleCommand ("ToolBox", Translations.GetString ("Tool Box"), null, null);
 		Rulers = new ToggleCommand ("Rulers", Translations.GetString ("Rulers"), null, Resources.Icons.ViewRulers);
 		RulerMetric = Gio.SimpleAction.NewStateful ("rulermetric", GtkExtensions.IntVariantType, GLib.Variant.NewInt32 (0));
+		ColorScheme = Gio.SimpleAction.NewStateful ("colorscheme", GtkExtensions.IntVariantType, GLib.Variant.NewInt32 (0));
 		Fullscreen = new Command ("Fullscreen", Translations.GetString ("Fullscreen"), null, Resources.StandardIcons.DocumentNew);
 
 		ZoomCollection = default_zoom_levels;
@@ -169,6 +171,17 @@ public void RegisterActions (Gtk.Application app, Gio.Menu menu)
 
 		app.AddAction (ImageTabs);
 		show_hide_menu.AppendItem (ImageTabs.CreateMenuItem ());
+
+		var color_scheme_section = Gio.Menu.New ();
+		menu.AppendSection (null, color_scheme_section);
+
+		var color_scheme_menu = Gio.Menu.New ();
+		color_scheme_section.AppendSubmenu (Translations.GetString ("Color Scheme"), color_scheme_menu);
+
+		app.AddAction (ColorScheme);
+		color_scheme_menu.Append (Translations.GetString ("Default"), $"app.{ColorScheme.Name}(0)");
+		color_scheme_menu.Append (Translations.GetString ("Light"), $"app.{ColorScheme.Name}(1)");
+		color_scheme_menu.Append (Translations.GetString ("Dark"), $"app.{ColorScheme.Name}(2)");
 	}
 
 	public void CreateStatusBar (Box statusbar)

Pinta/Actions/View/ColorSchemeChangedAction.cs

@@ -0,0 +1,33 @@
+using Gio;
+using Pinta.Core;
+
+namespace Pinta.Actions;
+
+internal sealed class ColorSchemeChangedAction : IActionHandler
+{
+	#region IActionHandler Members
+	public void Initialize ()
+	{
+		PintaCore.Actions.View.ColorScheme.OnActivate += Activated;
+	}
+
+	public void Uninitialize ()
+	{
+		PintaCore.Actions.View.ColorScheme.OnActivate -= Activated;
+	}
+	#endregion
+
+	private void Activated (SimpleAction action, SimpleAction.ActivateSignalArgs args)
+	{
+		action.ChangeState (args.Parameter!);
+
+		Adw.ColorScheme scheme = args.Parameter!.GetInt32 () switch {
+			1 => Adw.ColorScheme.ForceLight,
+			2 => Adw.ColorScheme.ForceDark,
+			_ => Adw.ColorScheme.PreferDark, // Use dark unless the system prefers light
+		};
+
+		Adw.StyleManager.GetDefault ().SetColorScheme (scheme);
+	}
+}
+

Pinta/DialogHandlers.cs

@@ -72,6 +72,7 @@ public ActionHandlers ()
 			new ImageTabsToggledAction (),
 			new StatusBarToggledAction (),
 			new ToolBoxToggledAction (),
+			new ColorSchemeChangedAction (),
 
 			// Window
 			new CloseAllDocumentsAction (),

Pinta/Main.cs

@@ -76,9 +76,6 @@ private static void OpenMainWindow (int threads, IEnumerable<string> files)
 	{
 		GLib.UnhandledException.SetHandler (OnUnhandledException);
 
-		// For testing a dark variant of the theme.
-		//Gtk.Settings.Default.SetProperty("gtk-application-prefer-dark-theme", new GLib.Value(true));
-
 		Gsk.Module.Initialize ();
 		Pango.Module.Initialize ();
 		PangoCairo.Module.Initialize ();

Pinta/MainWindow.cs

@@ -217,7 +217,7 @@ private bool HandleGlobalKeyPress (Gtk.EventControllerKey controller, Gtk.EventC
 			var canvas_window = ((PintaCanvas) PintaCore.Workspace.ActiveWorkspace.Canvas).CanvasWindow;
 
 			if ((canvas_window.Canvas.HasFocus || canvas_window.IsMouseOnCanvas) &&
-			     canvas_window.Canvas.DoKeyPressEvent (controller, args)) {
+				 canvas_window.Canvas.DoKeyPressEvent (controller, args)) {
 				return true;
 			}
 		}
@@ -458,6 +458,9 @@ private void LoadUserSettings ()
 
 		var ruler_metric = (MetricType) PintaCore.Settings.GetSetting ("ruler-metric", (int) MetricType.Pixels);
 		PintaCore.Actions.View.RulerMetric.Activate (GLib.Variant.NewInt32 ((int) ruler_metric));
+
+		int color_scheme = PintaCore.Settings.GetSetting ("color-scheme", 0);
+		PintaCore.Actions.View.ColorScheme.Activate (GLib.Variant.NewInt32 (color_scheme));
 	}
 
 	private void SaveUserSettings ()
@@ -471,6 +474,7 @@ private void SaveUserSettings ()
 		}
 
 		PintaCore.Settings.PutSetting ("ruler-metric", (int) GetCurrentRulerMetric ());
+		PintaCore.Settings.PutSetting ("color-scheme", PintaCore.Actions.View.ColorScheme.GetState ()!.GetInt32 ());
 		PintaCore.Settings.PutSetting ("window-maximized", window_shell.Window.IsMaximized ());
 		PintaCore.Settings.PutSetting ("ruler-shown", PintaCore.Actions.View.Rulers.Value);
 		PintaCore.Settings.PutSetting ("image-tabs-shown", PintaCore.Actions.View.ImageTabs.Value);