Fix regression with canvas focus introduced by 50863f2

When the root canvas window was made focusable instead of the canvas drawing area widget, this broke other code which explicitly was trying to make the drawing area focusable. All code now tries to set focus on the root canvas window, which from the changes in 50863f2 is the ideal choice to avoid unexpected scrolling while zoomed in

Fixes: #2070032

Pinta.Core/Classes/DocumentWorkspace.cs

@@ -52,6 +52,7 @@ internal DocumentWorkspace (Document document)
 
 	#region Public Properties
 	public Gtk.DrawingArea Canvas { get; set; } = null!; // NRT - This is set soon after creation
+	public Gtk.Widget CanvasWindow { get; set; } = null!; // NRT - This is set soon after creation
 
 	/// <summary>
 	/// Returns whether the zoomed image fits in the window without requiring scrolling.
@@ -177,6 +178,19 @@ public void InvalidateWindowRect (RectangleI windowRect)
 		OnCanvasInvalidated (new CanvasInvalidatedEventArgs (windowRect));
 	}
 
+	/// <summary>
+	/// Grabs focus to the canvas widget. This can be used to avoid leaving focus in
+	/// toolbar widgets, for example.
+	/// </summary>
+	public void GrabFocusToCanvas ()
+	{
+		bool gained_focus = CanvasWindow.GrabFocus ();
+		// Log a warning if something went wrong, e.g. there is a non-focusable widget
+		// in the hierarchy.
+		if (!gained_focus)
+			Console.Error.WriteLine ("Failed to gain focus on the canvas widget!");
+	}
+
 	/// <summary>
 	/// Determines whether the rectangle lies (at least partially) outside the canvas area.
 	/// </summary>

Pinta.Core/Extensions/Gtk/GtkExtensions.Widget.cs

@@ -120,7 +120,7 @@ public static Gtk.SpinButton CreateToolBarSpinButton (
 		// tools can handle subsequent key events.
 		spin.OnValueChanged += (o, e) => {
 			if (PintaCore.Workspace.HasOpenDocuments)
-				PintaCore.Workspace.ActiveWorkspace.Canvas.GrabFocus ();
+				PintaCore.Workspace.ActiveWorkspace.GrabFocusToCanvas ();
 		};
 		return spin;
 	}

Pinta.Gui.Widgets/Widgets/Canvas/CanvasWindow.cs

@@ -79,9 +79,9 @@ public CanvasWindow (
 		scroll_controller.OnDecelerate += (_, _) => gesture_zoom.IsActive (); // Cancel scroll deceleration when zooming
 		vp.AddController (scroll_controller);
 
-		// The mouse handler in PintaCanvas grabs focus away from toolbar widgets.
+		// The mouse handler in PintaCanvas grabs focus away from toolbar widgets, along
+		// with DocumentWorkpace.GrabFocusToCanvas()
 		Focusable = true;
-
 		Canvas = new PintaCanvas (this, document, canvasGrid) { Name = "canvas" };
 
 		// Rulers

Pinta.Tools/Tools/TextTool.cs

@@ -334,7 +334,7 @@ protected override void OnSaveSettings (ISettingsService settings)
 	private void HandleFontChanged (object? sender, EventArgs e)
 	{
 		if (workspace.HasOpenDocuments)
-			workspace.ActiveDocument.Workspace.Canvas.GrabFocus ();
+			workspace.ActiveDocument.Workspace.GrabFocusToCanvas ();
 
 		UpdateFont ();
 	}

Pinta/MainWindow.cs

@@ -117,7 +117,7 @@ public void Activate ()
 
 	private void Workspace_DocumentClosed (object? sender, DocumentEventArgs e)
 	{
-		var tab = FindTabWithCanvas ((PintaCanvas) e.Document.Workspace.Canvas);
+		var tab = FindTabWithCanvas ((CanvasWindow) e.Document.Workspace.CanvasWindow);
 
 		if (tab != null)
 			canvas_pad.Notebook.RemoveTab (tab);
@@ -164,6 +164,7 @@ private void Workspace_DocumentCreated (object? sender, DocumentEventArgs e)
 			RulersVisible = PintaCore.Actions.View.Rulers.Value,
 			RulerMetric = GetCurrentRulerMetric ()
 		};
+		doc.Workspace.CanvasWindow = canvas;
 		doc.Workspace.Canvas = canvas.Canvas;
 
 		DocumentViewContent my_content = new (doc, canvas);
@@ -223,9 +224,9 @@ private bool HandleGlobalKeyPress (
 		// first shot at handling the event if
 		// the mouse pointer is on the canvas
 		if (PintaCore.Workspace.HasOpenDocuments) {
-			var canvas_window = ((PintaCanvas) PintaCore.Workspace.ActiveWorkspace.Canvas).CanvasWindow;
+			var canvas_window = (CanvasWindow) PintaCore.Workspace.ActiveWorkspace.CanvasWindow;
 
-			if ((canvas_window.Canvas.HasFocus || canvas_window.IsMouseOnCanvas) &&
+			if ((canvas_window.HasFocus || canvas_window.IsMouseOnCanvas) &&
 				 canvas_window.Canvas.DoKeyPressEvent (controller, args)) {
 				return true;
 			}
@@ -249,9 +250,9 @@ private void HandleGlobalKeyRelease (
 		// Give the Canvas (and by extension the tools)
 		// first shot at handling the event if
 		// the mouse pointer is on the canvas
-		var canvas_window = ((PintaCanvas) PintaCore.Workspace.ActiveWorkspace.Canvas).CanvasWindow;
+		var canvas_window = (CanvasWindow) PintaCore.Workspace.ActiveWorkspace.CanvasWindow;
 
-		if (canvas_window.Canvas.HasFocus || canvas_window.IsMouseOnCanvas)
+		if (canvas_window.HasFocus || canvas_window.IsMouseOnCanvas)
 			canvas_window.Canvas.DoKeyReleaseEvent (controller, args);
 	}
 
@@ -575,10 +576,10 @@ private void ZoomToWindow_Activated (object sender, EventArgs e)
 			int image_x = PintaCore.Workspace.ImageSize.Width;
 			int image_y = PintaCore.Workspace.ImageSize.Height;
 
-			var canvas_window = PintaCore.Workspace.ActiveWorkspace.Canvas.Parent!;
+			var canvas_viewport = PintaCore.Workspace.ActiveWorkspace.Canvas.Parent!;
 
-			int window_x = canvas_window.GetAllocatedWidth ();
-			int window_y = canvas_window.GetAllocatedHeight ();
+			int window_x = canvas_viewport.GetAllocatedWidth ();
+			int window_y = canvas_viewport.GetAllocatedHeight ();
 
 			double ratio =
 				(image_x / (double) window_x >= image_y / (double) window_y)
@@ -608,16 +609,16 @@ private void ActiveDocumentChanged (object? sender, EventArgs e)
 		PintaCore.Actions.View.ResumeZoomUpdate ();
 
 		var doc = PintaCore.Workspace.ActiveDocument;
-		var tab = FindTabWithCanvas ((PintaCanvas) doc.Workspace.Canvas);
+		var tab = FindTabWithCanvas ((CanvasWindow) doc.Workspace.CanvasWindow);
 
 		if (tab != null)
 			canvas_pad.Notebook.ActiveItem = tab;
 
-		doc.Workspace.Canvas.GrabFocus ();
+		doc.Workspace.GrabFocusToCanvas ();
 	}
 
-	private IDockNotebookItem? FindTabWithCanvas (PintaCanvas canvas) =>
+	private IDockNotebookItem? FindTabWithCanvas (CanvasWindow canvas_window) =>
 		canvas_pad.Notebook.Items
-		.Where (i => ((CanvasWindow) i.Widget).Canvas == canvas)
+		.Where (i => ((CanvasWindow) i.Widget) == canvas_window)
 		.FirstOrDefault ();
 }