Samples: add ImageDrawn-Widget to test the override-chain

Source/Samples/Samples.csproj

@@ -10,6 +10,7 @@
     <EmbeddedResource Include="**\*.glade">
       <LogicalName>%(Filename)%(Extension)</LogicalName>
     </EmbeddedResource>
+    <EmbeddedResource Include="Testpic.png" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="Sections\**\*.cs" Visible="false">

Source/Samples/Sections/Widgets/CustomWidgets/ImageDrawn.cs

@@ -0,0 +1,110 @@
+// adopted from: https://github.com/mono/xwt/blob/master/Xwt.XamMac/Xwt.Mac/ImageHandler.cs
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Gtk;
+using Gdk;
+using System.Runtime.InteropServices;
+using Cairo;
+using Rectangle = Gdk.Rectangle;
+
+namespace Samples
+{
+	// This is a completely pointless widget, but its for testing subclassing Widget.OnDrawn
+	public class GtkDrawingArea : Gtk.DrawingArea { }
+
+	public class ImageBox : GtkDrawingArea
+	{
+		Pixbuf image;
+		float yalign = 0.5f, xalign = 0.5f;
+
+		public ImageBox(Pixbuf img) : this()
+		{
+			Image = img;
+		}
+
+		public ImageBox()
+		{
+			this.HasWindow = false;
+			this.AppPaintable = true;
+		}
+
+		public Pixbuf Image {
+			get { return image; }
+			set {
+				image = value;
+				SetSizeRequest((int) image.Width, (int) image.Height);
+				//QueueDraw();
+			}
+		}
+
+		private Size SizeRequestet { get; set; }
+
+		public float Yalign {
+			get { return yalign; }
+			set {
+				yalign = value;
+				QueueDraw();
+			}
+		}
+
+		public float Xalign {
+			get { return xalign; }
+			set {
+				xalign = value;
+				QueueDraw();
+			}
+		}
+		
+		void DrawPixbuf(Cairo.Context ctx, Gdk.Pixbuf img, double x, double y, Size idesc)
+		{
+			ctx.Save();
+			ctx.Translate(x, y);
+
+			ctx.Scale(idesc.Width / (double) img.Width, idesc.Height / (double) img.Height);
+			Gdk.CairoHelper.SetSourcePixbuf(ctx, img, 0, 0);
+
+#pragma warning disable 618
+			using (var p = ctx.Source) {
+				if (p is SurfacePattern pattern) {
+					if (idesc.Width > img.Width || idesc.Height > img.Height) {
+						// Fixes blur issue when rendering on an image surface
+						pattern.Filter = Cairo.Filter.Fast;
+					} else
+						pattern.Filter = Cairo.Filter.Good;
+				}
+			}
+#pragma warning restore 618
+
+
+			ctx.Paint();
+
+			ctx.Restore();
+		}
+
+		protected override bool OnDrawn(Cairo.Context cr)
+		{
+			if (image == default)
+				return true;
+			var a = Allocation;
+			var size = Allocation.Size;
+			Pixbuf pixbuff = image;
+			// HACK: Gtk sends sometimes an expose/draw event while the widget reallocates.
+			//       In that case we would draw in the wrong area, which may lead to artifacts
+			//       if no other widget updates it. Alternative: we could clip the
+			//       allocation bounds, but this may have other issues.
+			if (a.Width == 1 && a.Height == 1 && a.X == -1 && a.Y == -1) // the allocation coordinates on reallocation
+				return base.OnDrawn(cr);
+
+			var x = (int) ((a.Width - (float) pixbuff.Width) * xalign);
+			var y = (int) ((a.Height - (float) pixbuff.Height) * yalign);
+			if (x < 0) x = 0;
+			if (y < 0) y = 0;
+			DrawPixbuf(cr, pixbuff, x, y, size);
+			return base.OnDrawn(cr);
+		}
+	}
+}

Source/Samples/Sections/Widgets/ImageSection.cs

@@ -0,0 +1,50 @@
+// This is free and unencumbered software released into the public domain.
+// Happy coding!!! - GtkSharp Team
+
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Atk;
+using Gdk;
+using Gtk;
+
+namespace Samples
+{
+	[Section(ContentType = typeof(ImageBox), Category = Category.Widgets)]
+	class ImageSection : ListSection
+	{
+		public ImageSection()
+		{
+			AddItem(CreateContainer());
+		}
+
+		public (string, Widget) CreateContainer()
+		{
+			Stream GetResourceStream(Assembly assembly, string name)
+			{
+				var resources = assembly.GetManifestResourceNames();
+				var resourceName = resources.SingleOrDefault(str => str == name);
+
+				// try harder:
+				if (resourceName == default) {
+					resourceName = resources.SingleOrDefault(str => str.EndsWith(name));
+				}
+
+				if (resourceName == default)
+					return default;
+				var stream = assembly.GetManifestResourceStream(resourceName);
+				return stream;
+			}
+			Pixbuf image = default;
+			using (var stream = GetResourceStream(typeof(ImageSection).Assembly, "Testpic.png")) {
+				image = new Pixbuf(stream);
+			}
+
+			var container = new ImageBox(image);
+
+
+			return ($"{nameof(ImageBox)}:", container);
+		}
+	}
+}