[GTK] Some Shapes API support (1st part)

Supported Shapes:
  - Ellipse
  - Rectangle
  - Path

Supported Path Segments:
  - Arc
  - Line

Supported Brushes:
  - SolidColorBrush

Upstream PR: xamarin#14235

Co-authored-by: Afshin Arani <[email protected]>

Author: knocte

Xamarin.Forms.Platform.GTK/Controls/Shapes/EllipseView.cs

@@ -0,0 +1,21 @@
+using System;
+using Cairo;
+using Xamarin.Forms.Platform.GTK.Extensions;
+
+namespace Xamarin.Forms.Platform.GTK.Controls
+{
+	public class EllipseView : ShapeView
+	{
+		protected override void Draw(Gdk.Rectangle area, Context cr)
+		{
+			double width = _width;
+			double height = _height;
+
+			cr.Translate(width / 2, height / 2);
+			cr.Scale(width / 2, height / 2);
+			cr.Arc(0, 0, 1, 0, 2 * Math.PI);
+
+			base.Draw(area, cr);
+		}
+	}
+}

Xamarin.Forms.Platform.GTK/Controls/Shapes/PathView.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using Cairo;
+using Gdk;
+using Xamarin.Forms.Platform.GTK.Extensions;
+using Xamarin.Forms.Shapes;
+
+namespace Xamarin.Forms.Platform.GTK.Controls
+{
+	public class PathView : ShapeView
+	{
+		private PathGeometry _geometry;
+
+		public void UpdateGeometry(PathGeometry geometry)
+		{
+			_geometry = geometry;
+			QueueDraw();
+		}
+
+		protected override void Draw(Gdk.Rectangle area, Context cr)
+		{
+			cr.FillRule = _geometry.FillRule == Shapes.FillRule.EvenOdd ? Cairo.FillRule.EvenOdd : Cairo.FillRule.Winding;
+
+			foreach (var figure in _geometry.Figures)
+			{
+				cr.MoveTo(figure.StartPoint.X, figure.StartPoint.Y);
+
+				Point lastPoint = figure.StartPoint;
+
+				foreach (var segment in figure.Segments)
+				{
+					if (segment is LineSegment lineSegment)
+					{
+						cr.LineTo(lineSegment.Point.X, lineSegment.Point.Y);
+
+						lastPoint = lineSegment.Point;
+					}
+					else if (segment is ArcSegment arcSegment)
+					{
+						List<Point> points = new List<Point>();
+
+						GeometryHelper.FlattenArc(points,
+							lastPoint,
+							arcSegment.Point,
+							arcSegment.Size.Width,
+							arcSegment.Size.Height,
+							arcSegment.RotationAngle,
+							arcSegment.IsLargeArc,
+							arcSegment.SweepDirection == SweepDirection.CounterClockwise,
+							1);
+
+						for (int i = 0; i < points.Count; i++)
+						{
+							cr.LineTo(points[i].X, points[i].Y);
+						}
+
+						if (points.Count > 0)
+							lastPoint = points[points.Count - 1];
+
+					}
+				}
+
+				if (figure.IsClosed)
+					cr.ClosePath();
+			}
+
+			base.Draw(area, cr);
+		}
+
+	}
+}

Xamarin.Forms.Platform.GTK/Controls/Shapes/RectangleView.cs

@@ -0,0 +1,16 @@
+using System;
+using Cairo;
+using Xamarin.Forms.Platform.GTK.Extensions;
+
+namespace Xamarin.Forms.Platform.GTK.Controls
+{
+	public class RectangleView : ShapeView
+	{
+		protected override void Draw(Gdk.Rectangle area, Context cr)
+		{
+			cr.Rectangle(0, 0, _width, _height);
+
+			base.Draw(area, cr);
+		}
+	}
+}

Xamarin.Forms.Platform.GTK/Controls/Shapes/ShapeView.cs

@@ -0,0 +1,77 @@
+using System;
+using Cairo;
+using Xamarin.Forms.Platform.GTK.Extensions;
+
+namespace Xamarin.Forms.Platform.GTK.Controls
+{
+	public class ShapeView : GtkFormsContainer
+	{
+		protected Brush _fill, _stroke;
+		protected int _height, _width;
+		double? _strokeThickness;
+		float? _strokeDashOffset, _strokeMiterLimit;
+		double[] _dashArray;
+		LineCap? _strokeCap;
+		LineJoin? _strokeJoin;
+
+		public void UpdateFill(Brush brush)
+		{
+			_fill = brush;
+			QueueDraw();
+		}
+
+		public void UpdateStroke(Brush brush)
+		{
+			_stroke = brush;
+		}
+
+		public void UpdateSize(int height, int width)
+		{
+			_height = height;
+			_width = width;
+			QueueDraw();
+		}
+
+		public void UpdateStrokeThickness(double strokeThickness)
+		{
+			_strokeThickness = strokeThickness;
+		}
+
+		public void UpdateStrokeDashArray(double[] dashArray)
+		{
+			_dashArray = dashArray;
+		}
+
+		public void UpdateStrokeDashOffset(float strokeDashOffset)
+		{
+			_strokeDashOffset = strokeDashOffset;
+		}
+
+		public void UpdateStrokeLineCap(LineCap strokeCap)
+		{
+			_strokeCap = strokeCap;
+		}
+
+		public void UpdateStrokeLineJoin(LineJoin strokeJoin)
+		{
+			_strokeJoin = strokeJoin;
+		}
+
+		public void UpdateStrokeMiterLimit(float strokeMiterLimit)
+		{
+			_strokeMiterLimit = strokeMiterLimit;
+			QueueDraw();
+		}
+
+		protected override void Draw(Gdk.Rectangle area, Context cr)
+		{
+			if (_fill is SolidColorBrush fillBrush)
+			{
+				cr.SetSourceRGBA(fillBrush.Color.R, fillBrush.Color.G, fillBrush.Color.B, fillBrush.Color.A);
+				cr.FillPreserve();
+			}
+			else if (_fill != null)
+				throw new NotImplementedException("Brushes other than SolidColorBrush are not implemented yet");
+		}
+	}
+}

Xamarin.Forms.Platform.GTK/Properties/AssemblyInfo.cs

@@ -48,3 +48,7 @@
 [assembly: ExportCell(typeof(Xamarin.Forms.ImageCell), typeof(ImageCellRenderer))]
 [assembly: ExportCell(typeof(Xamarin.Forms.SwitchCell), typeof(SwitchCellRenderer))]
 [assembly: ExportCell(typeof(Xamarin.Forms.ViewCell), typeof(ViewCellRenderer))]
+
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Shapes.Rectangle), typeof(RectangleRenderer))]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Shapes.Ellipse), typeof(EllipseRenderer))]
+[assembly: ExportRenderer(typeof(Xamarin.Forms.Shapes.Path), typeof(PathRenderer))]

Xamarin.Forms.Platform.GTK/Renderers/Shapes/EllipseRenderer.cs

@@ -0,0 +1,13 @@
+using System;
+using System.ComponentModel;
+using Xamarin.Forms.Platform.GTK.Controls;
+using Xamarin.Forms.Platform.GTK.Extensions;
+using Xamarin.Forms.PlatformConfiguration.GTKSpecific;
+using Xamarin.Forms.Shapes;
+
+namespace Xamarin.Forms.Platform.GTK.Renderers
+{
+	public class EllipseRenderer : ShapeRenderer<Ellipse, EllipseView>
+	{
+	}
+}

Xamarin.Forms.Platform.GTK/Renderers/Shapes/PathRenderer.cs

@@ -0,0 +1,35 @@
+using System;
+using System.ComponentModel;
+using Xamarin.Forms.Platform.GTK.Controls;
+using Xamarin.Forms.Platform.GTK.Extensions;
+using Xamarin.Forms.PlatformConfiguration.GTKSpecific;
+using Xamarin.Forms.Shapes;
+
+namespace Xamarin.Forms.Platform.GTK.Renderers
+{
+	public class PathRenderer : ShapeRenderer<Path, PathView>
+	{
+		protected override void OnElementChanged(ElementChangedEventArgs<Path> e)
+		{
+			base.OnElementChanged(e);
+
+			if (e.NewElement != null)
+			{
+				SetData(Element.Data);
+			}
+		}
+
+		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			base.OnElementPropertyChanged(sender, e);
+
+			if (e.PropertyName == Shapes.Path.DataProperty.PropertyName)
+				SetData(Element.Data);
+		}
+
+		void SetData(Geometry data)
+		{
+			Control.UpdateGeometry(data as PathGeometry);
+		}
+	}
+}

Xamarin.Forms.Platform.GTK/Renderers/Shapes/RectangleRenderer.cs

@@ -0,0 +1,13 @@
+using System;
+using System.ComponentModel;
+using Xamarin.Forms.Platform.GTK.Controls;
+using Xamarin.Forms.Platform.GTK.Extensions;
+using Xamarin.Forms.PlatformConfiguration.GTKSpecific;
+using FormsRectangle = Xamarin.Forms.Shapes.Rectangle;
+
+namespace Xamarin.Forms.Platform.GTK.Renderers
+{
+	public class RectangleRenderer : ShapeRenderer<FormsRectangle, RectangleView>
+	{
+	}
+}