Merge branch 'master' into master

native/Avalonia.Native/src/OSX/rendertarget.mm

@@ -111,7 +111,11 @@
         if(_renderbuffer != 0)
             glDeleteRenderbuffers(1, &_renderbuffer);
     }
-    CFRelease(surface);
+
+    if(surface != nullptr)
+    {
+        CFRelease(surface);
+    }
 }
 @end
 
@@ -145,6 +149,12 @@ static IAvnGlSurfaceRenderTarget* CreateGlRenderTarget(IOSurfaceRenderTarget* ta
 }
 
 - (void)resize:(AvnPixelSize)size withScale: (float) scale{
+
+    if(size.Height <= 0)
+        size.Height = 1;
+    if(size.Width <= 0)
+        size.Width = 1;
+
     @synchronized (lock) {
         if(surface == nil
            || surface->size.Width != size.Width

src/Avalonia.Controls/ContextMenu.cs

@@ -246,7 +246,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Opens the menu.
         /// </summary>
-        public override void Open() => throw new NotSupportedException();
+        public override void Open() => Open(null);
 
         /// <summary>
         /// Opens a context menu on the specified control.

tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs

@@ -44,6 +44,55 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void Open_Should_Use_Default_Control()
+        {
+            using (Application())
+            {
+                var sut = new ContextMenu();
+                var target = new Panel
+                {
+                    ContextMenu = sut
+                };
+
+                var window = new Window { Content = target };
+                window.ApplyTemplate();
+                window.Presenter.ApplyTemplate();
+
+                bool opened = false;
+
+                sut.MenuOpened += (sender, args) =>
+                {
+                    opened = true;
+                };
+
+                sut.Open();
+
+                Assert.True(opened);
+            }
+        }
+
+        [Fact]
+        public void Open_Should_Raise_Exception_If_AlreadyDetached()
+        {
+            using (Application())
+            {
+                var sut = new ContextMenu();
+                var target = new Panel
+                {
+                    ContextMenu = sut
+                };
+
+                var window = new Window { Content = target };
+                window.ApplyTemplate();
+                window.Presenter.ApplyTemplate();
+
+                target.ContextMenu = null;
+
+               Assert.ThrowsAny<Exception>(()=> sut.Open());
+            }
+        }
+
         [Fact]
         public void Closing_Raises_Single_Closed_Event()
         {