Reduce overhead of pushing existing navigation stack (#672)

* Make StackCopy less awkward

* Clean up comment

* Update docs

* Update docs

* Replace SecondToLast with an arbitrarily deep Peek method

* Update docs

* Handle negative depths in Peek()

diff --git a/Xamarin.Forms.Core.UnitTests/NavigationUnitTest.cs b/Xamarin.Forms.Core.UnitTests/NavigationUnitTest.cs
index 1cc3ac6..7118e14 100644 (file)
--- a/Xamarin.Forms.Core.UnitTests/NavigationUnitTest.cs
+++ b/Xamarin.Forms.Core.UnitTests/NavigationUnitTest.cs
@@ -213,29 +213,94 @@ namespace Xamarin.Forms.Core.UnitTests
                }
 
                [Test]
-               public async Task TestStackCopy ()
+               public async Task PeekOne()
                {
-                       var nav = new NavigationPage ();
+                       var nav = new NavigationPage();
 
                        bool signaled = false;
                        nav.PoppedToRoot += (sender, args) => signaled = true;
 
-                       var root = new ContentPage {Content = new View ()};
-                       var child1 = new ContentPage {Content = new View ()};
-                       var child2 = new ContentPage {Content = new View ()};
+                       var root = new ContentPage { Content = new View() };
+                       var child1 = new ContentPage { Content = new View() };
+                       var child2 = new ContentPage { Content = new View() };
 
-                       await nav.PushAsync (root);
-                       await nav.PushAsync (child1);
-                       await nav.PushAsync (child2);
+                       await nav.PushAsync(root);
+                       await nav.PushAsync(child1);
+                       await nav.PushAsync(child2);
+
+                       Assert.AreEqual(((INavigationPageController)nav).Peek(1), child1);
+               }
 
-                       var copy = ((INavigationPageController)nav).StackCopy;
+               [Test]
+               public async Task PeekZero()
+               {
+                       var nav = new NavigationPage();
 
-                       Assert.AreEqual (child2, copy.Pop ());
-                       Assert.AreEqual (child1, copy.Pop ());
-                       Assert.AreEqual (root, copy.Pop ());
+                       bool signaled = false;
+                       nav.PoppedToRoot += (sender, args) => signaled = true;
+
+                       var root = new ContentPage { Content = new View() };
+                       var child1 = new ContentPage { Content = new View() };
+                       var child2 = new ContentPage { Content = new View() };
+
+                       await nav.PushAsync(root);
+                       await nav.PushAsync(child1);
+                       await nav.PushAsync(child2);
+
+                       Assert.AreEqual(((INavigationPageController)nav).Peek(0), child2);
                }
 
                [Test]
+               public async Task PeekPastStackDepth()
+               {
+                       var nav = new NavigationPage();
+
+                       bool signaled = false;
+                       nav.PoppedToRoot += (sender, args) => signaled = true;
+
+                       var root = new ContentPage { Content = new View() };
+                       var child1 = new ContentPage { Content = new View() };
+                       var child2 = new ContentPage { Content = new View() };
+
+                       await nav.PushAsync(root);
+                       await nav.PushAsync(child1);
+                       await nav.PushAsync(child2);
+
+                       Assert.AreEqual(((INavigationPageController)nav).Peek(3), null);
+               }
+
+               [Test]
+               public async Task PeekShallow()
+               {
+                       var nav = new NavigationPage();
+
+                       bool signaled = false;
+                       nav.PoppedToRoot += (sender, args) => signaled = true;
+
+                       var root = new ContentPage { Content = new View() };
+                       var child1 = new ContentPage { Content = new View() };
+                       var child2 = new ContentPage { Content = new View() };
+
+                       await nav.PushAsync(root);
+                       await nav.PushAsync(child1);
+                       await nav.PushAsync(child2);
+
+                       Assert.AreEqual(((INavigationPageController)nav).Peek(-1), null);
+               }
+
+               [Test]
+               public async Task PeekEmpty([Range(0, 3)] int depth)
+               {
+                       var nav = new NavigationPage();
+
+                       bool signaled = false;
+                       nav.PoppedToRoot += (sender, args) => signaled = true;
+
+                       Assert.AreEqual(((INavigationPageController)nav).Peek(depth), null);
+               }
+
+
+               [Test]
                public void ConstructWithRoot ()
                {
                        var root = new ContentPage ();

diff --git a/Xamarin.Forms.Core/INavigationPageController.cs b/Xamarin.Forms.Core/INavigationPageController.cs
index eddbe75..d4ae867 100644 (file)
--- a/Xamarin.Forms.Core/INavigationPageController.cs
+++ b/Xamarin.Forms.Core/INavigationPageController.cs
@@ -7,7 +7,9 @@ namespace Xamarin.Forms
 {
        public interface INavigationPageController
        {
-               Stack<Page> StackCopy { get; }
+               Page Peek(int depth);
+
+               IEnumerable<Page> Pages { get; }
 
                int StackDepth { get; }
 

diff --git a/Xamarin.Forms.Core/NavigationPage.cs b/Xamarin.Forms.Core/NavigationPage.cs
index 7b393b9..fdafec0 100644 (file)
--- a/Xamarin.Forms.Core/NavigationPage.cs
+++ b/Xamarin.Forms.Core/NavigationPage.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Threading.Tasks;
 using Xamarin.Forms.Internals;
@@ -61,17 +62,23 @@ namespace Xamarin.Forms
 
                internal Task CurrentNavigationTask { get; set; }
 
-               Stack<Page> INavigationPageController.StackCopy
+               Page INavigationPageController.Peek(int depth)
                {
-                       get
+                       if (depth < 0)
                        {
-                               var result = new Stack<Page>(PageController.InternalChildren.Count);
-                               foreach (Page page in PageController.InternalChildren)
-                                       result.Push(page);
-                               return result;
+                               return null;
                        }
+
+                       if (PageController.InternalChildren.Count <= depth)
+                       {
+                               return null;
+                       }
+
+                       return (Page)PageController.InternalChildren[PageController.InternalChildren.Count - depth - 1];
                }
 
+               IEnumerable<Page> INavigationPageController.Pages => PageController.InternalChildren.Cast<Page>();
+
                int INavigationPageController.StackDepth
                {
                        get { return PageController.InternalChildren.Count; }

diff --git a/Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs b/Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs
index cab4d56..cc47429 100644 (file)
--- a/Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs
@@ -268,7 +268,7 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
                                navController.RemovePageRequested += OnRemovePageRequested;
 
                                // If there is already stuff on the stack we need to push it
-                               foreach (Page page in navController.StackCopy.Reverse())
+                               foreach (Page page in navController.Pages)
                                {
                                        PushViewAsync(page, false);
                                }
@@ -461,7 +461,7 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
                Task<bool> OnPopViewAsync(Page page, bool animated)
                {
-                       Page pageToShow = ((INavigationPageController)Element).StackCopy.Skip(1).FirstOrDefault();
+                       Page pageToShow = ((INavigationPageController)Element).Peek(1);
                        if (pageToShow == null)
                                return Task.FromResult(false);
 

diff --git a/Xamarin.Forms.Platform.Android/Renderers/NavigationRenderer.cs b/Xamarin.Forms.Platform.Android/Renderers/NavigationRenderer.cs
index c02dc42..bf6540b 100644 (file)
--- a/Xamarin.Forms.Platform.Android/Renderers/NavigationRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/NavigationRenderer.cs
@@ -109,7 +109,7 @@ namespace Xamarin.Forms.Platform.Android
                        newNavController.RemovePageRequested += OnRemovePageRequested;
 
                        // If there is already stuff on the stack we need to push it
-                       foreach(Page page in newNavController.StackCopy.Reverse())
+                       foreach (Page page in newNavController.Pages)
                        {
                                PushViewAsync(page, false);
                        }
@@ -130,7 +130,7 @@ namespace Xamarin.Forms.Platform.Android
 
                protected virtual Task<bool> OnPopViewAsync(Page page, bool animated)
                {
-                       Page pageToShow = ((INavigationPageController)Element).StackCopy.Skip(1).FirstOrDefault();
+                       Page pageToShow = ((INavigationPageController)Element).Peek(1);
                        if (pageToShow == null)
                                return Task.FromResult(false);
 

diff --git a/Xamarin.Forms.Platform.WP8/NavigationPageRenderer.cs b/Xamarin.Forms.Platform.WP8/NavigationPageRenderer.cs
index 1637b1d..e2837f0 100644 (file)
--- a/Xamarin.Forms.Platform.WP8/NavigationPageRenderer.cs
+++ b/Xamarin.Forms.Platform.WP8/NavigationPageRenderer.cs
@@ -139,7 +139,7 @@ namespace Xamarin.Forms.Platform.WinPhone
                        var platform = Element.Platform as Platform;
                        if (platform != null)
                        {
-                               if (e.Page == ((INavigationPageController)Element).StackCopy.LastOrDefault())
+                               if (e.Page == ((INavigationPageController)Element).Pages.FirstOrDefault()) 
                                        ((IPageController)e.Page).IgnoresContainerArea = true;
                                e.Task = platform.PushCore(e.Page, Element, e.Animated, e.Realize).ContinueWith((t, o) => true, null);
                        }

diff --git a/Xamarin.Forms.Platform.WinRT/NavigationPageRenderer.cs b/Xamarin.Forms.Platform.WinRT/NavigationPageRenderer.cs
index d6f4542..d5da8cd 100644 (file)
--- a/Xamarin.Forms.Platform.WinRT/NavigationPageRenderer.cs
+++ b/Xamarin.Forms.Platform.WinRT/NavigationPageRenderer.cs
@@ -398,7 +398,7 @@ namespace Xamarin.Forms.Platform.WinRT
 
                void OnPopRequested(object sender, NavigationRequestedEventArgs e)
                {
-                       var newCurrent = (Page)PageController.InternalChildren[PageController.InternalChildren.Count - 2];
+                       var newCurrent = ((INavigationPageController)Element).Peek(1);
                        SetPage(newCurrent, e.Animated, true);
                }
 
@@ -419,8 +419,10 @@ namespace Xamarin.Forms.Platform.WinRT
 
                void PushExistingNavigationStack()
                {
-                       for (int i = ((INavigationPageController)Element).StackCopy.Count - 1; i >= 0; i--)
-                               SetPage(((INavigationPageController)Element).StackCopy.ElementAt(i), false, false);
+                       foreach (var page in ((INavigationPageController)Element).Pages)
+                       {
+                               SetPage(page, false, false);
+                       }
                }
 
                void SetPage(Page page, bool isAnimated, bool isPopping)

diff --git a/Xamarin.Forms.Platform.iOS/Renderers/NavigationRenderer.cs b/Xamarin.Forms.Platform.iOS/Renderers/NavigationRenderer.cs
index 6b698f2..1465b8d 100644 (file)
--- a/Xamarin.Forms.Platform.iOS/Renderers/NavigationRenderer.cs
+++ b/Xamarin.Forms.Platform.iOS/Renderers/NavigationRenderer.cs
@@ -211,7 +211,7 @@ namespace Xamarin.Forms.Platform.iOS
                        UpdateBarTextColor();
 
                        // If there is already stuff on the stack we need to push it
-                       ((INavigationPageController)navPage).StackCopy.Reverse().ForEach(async p => await PushPageAsync(p, false));
+                       ((INavigationPageController)navPage).Pages.ForEach(async p => await PushPageAsync(p, false));
 
                        _tracker = new VisualElementTracker(this);
 
@@ -617,7 +617,7 @@ namespace Xamarin.Forms.Platform.iOS
                        if (containerController == null)
                                return;
                        var currentChild = containerController.Child;
-                       var firstPage = ((INavigationPageController)Element).StackCopy.LastOrDefault();
+                       var firstPage = ((INavigationPageController)Element).Pages.FirstOrDefault(); 
                        if ((firstPage != pageBeingRemoved && currentChild != firstPage && NavigationPage.GetHasBackButton(currentChild)) || _parentMasterDetailPage == null)
                                return;
 

diff --git a/docs/Xamarin.Forms.Core/Xamarin.Forms/INavigationPageController.xml b/docs/Xamarin.Forms.Core/Xamarin.Forms/INavigationPageController.xml
index b72feb0..95aeae7 100644 (file)
--- a/docs/Xamarin.Forms.Core/Xamarin.Forms/INavigationPageController.xml
+++ b/docs/Xamarin.Forms.Core/Xamarin.Forms/INavigationPageController.xml
@@ -26,6 +26,42 @@
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
+    <Member MemberName="Pages">
+      <MemberSignature Language="C#" Value="public System.Collections.Generic.IEnumerable&lt;Xamarin.Forms.Page&gt; Pages { get; }" />
+      <MemberSignature Language="ILAsm" Value=".property instance class System.Collections.Generic.IEnumerable`1&lt;class Xamarin.Forms.Page&gt; Pages" />
+      <MemberType>Property</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Collections.Generic.IEnumerable&lt;Xamarin.Forms.Page&gt;</ReturnType>
+      </ReturnValue>
+      <Docs>
+        <summary>To be added.</summary>
+        <value>To be added.</value>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
+    <Member MemberName="Peek">
+      <MemberSignature Language="C#" Value="public Xamarin.Forms.Page Peek (int depth);" />
+      <MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance class Xamarin.Forms.Page Peek(int32 depth) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>Xamarin.Forms.Page</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="depth" Type="System.Int32" />
+      </Parameters>
+      <Docs>
+        <param name="depth">To be added.</param>
+        <summary>To be added.</summary>
+        <returns>To be added.</returns>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
     <Member MemberName="PopAsyncInner">
       <MemberSignature Language="C#" Value="public System.Threading.Tasks.Task&lt;Xamarin.Forms.Page&gt; PopAsyncInner (bool animated, bool fast = false);" />
       <MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance class System.Threading.Tasks.Task`1&lt;class Xamarin.Forms.Page&gt; PopAsyncInner(bool animated, bool fast) cil managed" />
@@ -108,22 +144,6 @@
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
-    <Member MemberName="StackCopy">
-      <MemberSignature Language="C#" Value="public System.Collections.Generic.Stack&lt;Xamarin.Forms.Page&gt; StackCopy { get; }" />
-      <MemberSignature Language="ILAsm" Value=".property instance class System.Collections.Generic.Stack`1&lt;class Xamarin.Forms.Page&gt; StackCopy" />
-      <MemberType>Property</MemberType>
-      <AssemblyInfo>
-        <AssemblyVersion>2.0.0.0</AssemblyVersion>
-      </AssemblyInfo>
-      <ReturnValue>
-        <ReturnType>System.Collections.Generic.Stack&lt;Xamarin.Forms.Page&gt;</ReturnType>
-      </ReturnValue>
-      <Docs>
-        <summary>For internal use by platform renderers.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
-      </Docs>
-    </Member>
     <Member MemberName="StackDepth">
       <MemberSignature Language="C#" Value="public int StackDepth { get; }" />
       <MemberSignature Language="ILAsm" Value=".property instance int32 StackDepth" />

diff --git a/docs/Xamarin.Forms.Core/Xamarin.Forms/NavigationPage.xml b/docs/Xamarin.Forms.Core/Xamarin.Forms/NavigationPage.xml
index 77e203f..1094d15 100644 (file)
--- a/docs/Xamarin.Forms.Core/Xamarin.Forms/NavigationPage.xml
+++ b/docs/Xamarin.Forms.Core/Xamarin.Forms/NavigationPage.xml
@@ -450,7 +450,7 @@
           <AttributeName>System.Diagnostics.DebuggerStepThrough</AttributeName>
         </Attribute>
         <Attribute>
-          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PopAsync&gt;d__38))</AttributeName>
+          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PopAsync&gt;d__39))</AttributeName>
         </Attribute>
       </Attributes>
       <ReturnValue>
@@ -548,7 +548,7 @@
           <AttributeName>System.Diagnostics.DebuggerStepThrough</AttributeName>
         </Attribute>
         <Attribute>
-          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PopToRootAsync&gt;d__46))</AttributeName>
+          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PopToRootAsync&gt;d__47))</AttributeName>
         </Attribute>
       </Attributes>
       <ReturnValue>
@@ -605,7 +605,7 @@
           <AttributeName>System.Diagnostics.DebuggerStepThrough</AttributeName>
         </Attribute>
         <Attribute>
-          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PushAsync&gt;d__48))</AttributeName>
+          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;PushAsync&gt;d__49))</AttributeName>
         </Attribute>
       </Attributes>
       <ReturnValue>
@@ -844,6 +844,42 @@ public class MyPage : NavigationPage
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
+    <Member MemberName="Xamarin.Forms.INavigationPageController.Pages">
+      <MemberSignature Language="C#" Value="System.Collections.Generic.IEnumerable&lt;Xamarin.Forms.Page&gt; Xamarin.Forms.INavigationPageController.Pages { get; }" />
+      <MemberSignature Language="ILAsm" Value=".property instance class System.Collections.Generic.IEnumerable`1&lt;class Xamarin.Forms.Page&gt; Xamarin.Forms.INavigationPageController.Pages" />
+      <MemberType>Property</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Collections.Generic.IEnumerable&lt;Xamarin.Forms.Page&gt;</ReturnType>
+      </ReturnValue>
+      <Docs>
+        <summary>To be added.</summary>
+        <value>To be added.</value>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
+    <Member MemberName="Xamarin.Forms.INavigationPageController.Peek">
+      <MemberSignature Language="C#" Value="Xamarin.Forms.Page INavigationPageController.Peek (int depth);" />
+      <MemberSignature Language="ILAsm" Value=".method hidebysig newslot virtual instance class Xamarin.Forms.Page Xamarin.Forms.INavigationPageController.Peek(int32 depth) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>Xamarin.Forms.Page</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="depth" Type="System.Int32" />
+      </Parameters>
+      <Docs>
+        <param name="depth">To be added.</param>
+        <summary>To be added.</summary>
+        <returns>To be added.</returns>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
     <Member MemberName="Xamarin.Forms.INavigationPageController.PopAsyncInner">
       <MemberSignature Language="C#" Value="System.Threading.Tasks.Task&lt;Xamarin.Forms.Page&gt; INavigationPageController.PopAsyncInner (bool animated, bool fast);" />
       <MemberSignature Language="ILAsm" Value=".method hidebysig newslot virtual instance class System.Threading.Tasks.Task`1&lt;class Xamarin.Forms.Page&gt; Xamarin.Forms.INavigationPageController.PopAsyncInner(bool animated, bool fast) cil managed" />
@@ -856,7 +892,7 @@ public class MyPage : NavigationPage
           <AttributeName>System.Diagnostics.DebuggerStepThrough</AttributeName>
         </Attribute>
         <Attribute>
-          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;Xamarin-Forms-INavigationPageController-PopAsyncInner&gt;d__63))</AttributeName>
+          <AttributeName>System.Runtime.CompilerServices.AsyncStateMachine(typeof(Xamarin.Forms.NavigationPage/&lt;Xamarin-Forms-INavigationPageController-PopAsyncInner&gt;d__64))</AttributeName>
         </Attribute>
       </Attributes>
       <ReturnValue>
@@ -874,22 +910,6 @@ public class MyPage : NavigationPage
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
-    <Member MemberName="Xamarin.Forms.INavigationPageController.StackCopy">
-      <MemberSignature Language="C#" Value="System.Collections.Generic.Stack&lt;Xamarin.Forms.Page&gt; Xamarin.Forms.INavigationPageController.StackCopy { get; }" />
-      <MemberSignature Language="ILAsm" Value=".property instance class System.Collections.Generic.Stack`1&lt;class Xamarin.Forms.Page&gt; Xamarin.Forms.INavigationPageController.StackCopy" />
-      <MemberType>Property</MemberType>
-      <AssemblyInfo>
-        <AssemblyVersion>2.0.0.0</AssemblyVersion>
-      </AssemblyInfo>
-      <ReturnValue>
-        <ReturnType>System.Collections.Generic.Stack&lt;Xamarin.Forms.Page&gt;</ReturnType>
-      </ReturnValue>
-      <Docs>
-        <summary>Internal</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
-      </Docs>
-    </Member>
     <Member MemberName="Xamarin.Forms.INavigationPageController.StackDepth">
       <MemberSignature Language="C#" Value="int Xamarin.Forms.INavigationPageController.StackDepth { get; }" />
       <MemberSignature Language="ILAsm" Value=".property instance int32 Xamarin.Forms.INavigationPageController.StackDepth" />