Shape alterations can provide displaying/displayed delegates

Enables components to add shapes binding alternates
Also provides a hook for the just-before-display preprocessing

--HG--
branch : dev

src/Orchard.Tests/DisplayManagement/Descriptors/DefaultShapeTableManagerTests.cs

@@ -3,6 +3,7 @@ using System.Linq;
 using Autofac;
 using NUnit.Framework;
 using Orchard.DisplayManagement.Descriptors;
+using Orchard.DisplayManagement.Implementation;
 using Orchard.Environment.Extensions.Models;
 
 namespace Orchard.Tests.DisplayManagement.Descriptors {
@@ -12,7 +13,9 @@ namespace Orchard.Tests.DisplayManagement.Descriptors {
             builder.RegisterType<DefaultShapeTableManager>().As<IShapeTableManager>();
 
             builder.RegisterType<TestShapeProvider>().As<IShapeTableProvider>()
-                .WithMetadata("Feature", TestFeature());
+                .WithMetadata("Feature", TestFeature())
+                .As<TestShapeProvider>()
+                .InstancePerLifetimeScope();
         }
 
         static Feature TestFeature() {
@@ -29,8 +32,12 @@ namespace Orchard.Tests.DisplayManagement.Descriptors {
         }
 
         public class TestShapeProvider : IShapeTableProvider {
-            public void Discover(ShapeTableBuilder builder) {
+
+            public Action<ShapeTableBuilder> Discover = x => { };
+
+            void IShapeTableProvider.Discover(ShapeTableBuilder builder) {
                 builder.Describe("Hello");
+                Discover(builder);
             }
         }
 
@@ -48,5 +55,29 @@ namespace Orchard.Tests.DisplayManagement.Descriptors {
             Assert.That(shapeTable1.Descriptors["Hello"], Is.Not.Null);
             Assert.That(shapeTable2.Descriptors["Hello"], Is.Not.Null);
         }
+
+        [Test]
+        public void CallbackAlterationsContributeToDescriptor() {
+            Action<ShapeCreatingContext> cb1 = x => { };
+            Action<ShapeCreatedContext> cb2 = x => { };
+            Action<ShapeDisplayingContext> cb3 = x => { };
+            Action<ShapeDisplayedContext> cb4 = x => { };
+
+            _container.Resolve<TestShapeProvider>().Discover =
+                builder => builder.Describe("Foo")
+                               .OnCreating(cb1)
+                               .OnCreated(cb2)
+                               .OnDisplaying(cb3)
+                               .OnDisplayed(cb4);
+
+            var manager = _container.Resolve<IShapeTableManager>();
+
+            var foo = manager.GetShapeTable(null).Descriptors["Foo"];
+
+            Assert.That(foo.Creating.Single(), Is.SameAs(cb1));
+            Assert.That(foo.Created.Single(), Is.SameAs(cb2));
+            Assert.That(foo.Displaying.Single(), Is.SameAs(cb3));
+            Assert.That(foo.Displayed.Single(), Is.SameAs(cb4));
+        }
     }
 }

src/Orchard/DisplayManagement/Descriptors/ShapeAlterationBuilder.cs

@@ -73,6 +73,20 @@ namespace Orchard.DisplayManagement.Descriptors {
                 descriptor.Created = existing.Concat(new[] { action });
             });
         }
+        
+        public ShapeAlterationBuilder OnDisplaying(Action<ShapeDisplayingContext> action) {
+            return Configure(descriptor => {
+                var existing = descriptor.Displaying ?? Enumerable.Empty<Action<ShapeDisplayingContext>>();
+                descriptor.Displaying = existing.Concat(new[] { action });
+            });
+        }
+
+        public ShapeAlterationBuilder OnDisplayed(Action<ShapeDisplayedContext> action) {
+            return Configure(descriptor => {
+                var existing = descriptor.Displayed ?? Enumerable.Empty<Action<ShapeDisplayedContext>>();
+                descriptor.Displayed = existing.Concat(new[] { action });
+            });
+        }
 
         public ShapeAlteration Build() {
             return new ShapeAlteration(_shapeType, _feature, _configurations.ToArray());