Measure Forms elements

Ooui.Forms/Extensions/ElementExtensions.cs

@@ -8,8 +8,14 @@ namespace Ooui.Forms.Extensions
         public static SizeRequest GetSizeRequest (this Ooui.Element self, double widthConstraint, double heightConstraint,
             double minimumWidth = -1, double minimumHeight = -1)
         {
-            var request = new Size (double.PositiveInfinity, double.PositiveInfinity);
-            var minimum = new Size (double.PositiveInfinity, double.PositiveInfinity);
+            Size s = self.Text.MeasureSize (self.Style);
+
+            var request = new Size (
+                double.IsPositiveInfinity (s.Width) ? double.PositiveInfinity : s.Width,
+                double.IsPositiveInfinity (s.Height) ? double.PositiveInfinity : s.Height);
+            var minimum = new Size (minimumWidth < 0 ? request.Width : minimumWidth,
+                minimumHeight < 0 ? request.Height : minimumHeight);
+
             return new SizeRequest (request, minimum);
         }
     }

Ooui.Forms/Extensions/FontExtensions.cs

@@ -21,5 +21,18 @@ namespace Ooui.Forms.Extensions
                     return "end";
             }
         }
+
+        public static Size MeasureSize (this string text, Style style)
+        {
+            if (string.IsNullOrEmpty (text))
+                return Size.Zero;
+
+            var fontHeight = 16.0;
+            var charWidth = 8.0;
+
+            var width = text.Length * charWidth;
+
+            return new Size (width, fontHeight);
+        }
     }
 }

Ooui.Forms/Forms.cs

@@ -78,7 +78,19 @@ namespace Xamarin.Forms
 
             public double GetNamedSize (NamedSize size, Type targetElementType, bool useOldSizes)
             {
-                throw new NotImplementedException ();
+                switch (size) {
+                    default:
+                    case NamedSize.Default:
+                        return 16;
+                    case NamedSize.Micro:
+                        return 9;
+                    case NamedSize.Small:
+                        return 12;
+                    case NamedSize.Medium:
+                        return 22;
+                    case NamedSize.Large:
+                        return 32;
+                }
             }
 
             public Task<Stream> GetStreamAsync (Uri uri, CancellationToken cancellationToken)

Ooui.Forms/IVisualElementRenderer.cs

@@ -14,5 +14,7 @@ namespace Ooui.Forms
 		void SetElement (VisualElement element);
 
 		void SetElementSize (Size size);
+
+        SizeRequest GetDesiredSize (double widthConstraint, double heightConstraint);
 	}
 }

Ooui.Forms/Platform.cs

@@ -70,7 +70,11 @@ namespace Ooui.Forms
 
         public SizeRequest GetNativeSize (VisualElement view, double widthConstraint, double heightConstraint)
         {
-            return new SizeRequest (new Size (100, 100));
+            var renderView = GetRenderer (view);
+            if (renderView == null || renderView.NativeView == null)
+                return new SizeRequest (Size.Zero);
+
+            return renderView.GetDesiredSize (widthConstraint, heightConstraint);
         }
 
         public void SetPage (Page newRoot)

Ooui.Forms/Renderers/LabelRenderer.cs

@@ -17,7 +17,7 @@ namespace Ooui.Forms.Renderers
         public override SizeRequest GetDesiredSize (double widthConstraint, double heightConstraint)
         {
             if (!_perfectSizeValid) {
-                _perfectSize = GetPerfectSize ();
+                _perfectSize = base.GetDesiredSize (double.PositiveInfinity, double.PositiveInfinity);
                 _perfectSize.Minimum = new Size (Math.Min (10, _perfectSize.Request.Width), _perfectSize.Request.Height);
                 _perfectSizeValid = true;
             }
@@ -50,11 +50,6 @@ namespace Ooui.Forms.Renderers
             return result;
         }
 
-        SizeRequest GetPerfectSize ()
-        {
-            return new SizeRequest (new Size (100, 22));
-        }
-
         protected override void OnElementChanged (ElementChangedEventArgs<Xamarin.Forms.Label> e)
         {
             if (e.NewElement != null) {

Samples/XamarinFormsSample.cs

@@ -6,35 +6,45 @@ namespace Samples
 {
 	public class XamarinFormsSample
 	{
-		public void Publish ()
+		Page MakePage ()
 		{
 			Forms.Init ();
 
 			var countLabel = new Label {
 				Text = "0",
                 BackgroundColor = Color.Gold,
+                HorizontalOptions = LayoutOptions.Center,
 			};
 			var countButton = new Button {
                 Text = "Increase",
-                VerticalOptions = LayoutOptions.FillAndExpand,
+                HorizontalOptions = LayoutOptions.FillAndExpand,
 			};
 			countButton.Clicked += (sender, e) => {
 				var v = int.Parse (countLabel.Text);
 				countLabel.Text = (v + 1).ToString ();
 			};
-			var page = new ContentPage {
-				Content = new StackLayout {
+            return new ContentPage {
+                Content = new StackLayout {
                     BackgroundColor = Color.Khaki,
-					Children = {
-						new Label { Text = "Hello World!" },
+                    Children = {
+                        new Label {
+                            Text = "Hello World!",
+                            FontSize = 32,
+                            HorizontalOptions = LayoutOptions.Center,
+                        },
 						countLabel,
 						countButton,
 					},
 				},
 			};
+        }
 
-			page.Publish ("/xamarin-forms");
-			page.PublishShared ("/xamarin-forms-shared");
-		}
+        public void Publish ()
+        {
+            var page = MakePage ();
+            page.Publish ("/xamarin-forms-shared");
+
+            Ooui.UI.Publish ("/xamarin-forms", () => MakePage ().CreateElement ());
+        }
 	}
 }