Fix up the login button bindings and positioning

src/GitHub.App/ViewModels/LoginControlViewModel.cs

@@ -156,8 +156,8 @@ namespace GitHub.ViewModels
 
             var canLogin = this.WhenAny(x => x.IsValid, x => x.Value);
 
-            this.WhenAny(x => x.LoginFailed, x => x.Value ? "Try again" : "Log in")
-                .ToProperty(this, x => x.LoginButtonText, out loginButtonText);
+            loginButtonText = this.WhenAny(x => x.LoginFailed, x => x.Value ? "Try again" : "Log in")
+                .ToProperty(this, x => x.LoginButtonText, initialValue: "Log In");
 
             LoginPrefix = "Log in";
             LoginFailedText = "Log in failed";

src/GitHub.Exports/ViewModels/ILoginViewModel.cs

@@ -8,6 +8,8 @@ namespace GitHub.ViewModels
     {
         string UsernameOrEmail { get; set; }
         string Password { get; set; }
+        string LoginButtonText { get; }
+        bool IsLoginInProgress { get; }
         ICommand LoginCmd { get; }
         IObservable<AuthenticationResult> AuthenticationResults { get; }
     }

src/GitHub.VisualStudio/UI/Views/Controls/LoginControl.xaml

@@ -196,9 +196,14 @@
                 Text="{Binding EnterpriseUrl, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True, NotifyOnValidationError=True}"
                 Validation.ErrorTemplate="{DynamicResource ValidationAdorner}" />
 
-            <StackPanel Orientation="Horizontal" IsEnabled="{Binding IsLoginInProgress, Converter={ui:InverseBooleanConverter}}" Margin="0,12,0,0">
-                <ui:OcticonCircleButton x:Name="loginButton" Icon="check" Content="{Binding LoginButtonText, FallbackValue=Log In}" IsDefault="True" />
-            </StackPanel>
+            <Border HorizontalAlignment="Center"  Margin="0,12,0,0">
+                <ui:OcticonCircleButton
+                    x:Name="loginButton"
+                    Icon="check"
+                    Content="Log In"
+                    IsEnabled="true"
+                    IsDefault="True" />
+            </Border>
 
             <StackPanel x:Name="gitHubSignupStackPanel">
                 <TextBlock x:Name="signUpLabel" Style="{DynamicResource GitHubH1TextBlock}" Text="Sign up" Margin="0,10,0,0" />

src/GitHub.VisualStudio/UI/Views/Controls/LoginControl.xaml.cs

@@ -28,6 +28,8 @@ namespace GitHub.VisualStudio.UI.Views.Controls
             {
                 d(this.Bind(ViewModel, vm => vm.UsernameOrEmail, v => v.usernameOrEmailTextBox.Text));
                 d(this.Bind(ViewModel, vm => vm.Password, v => v.passwordTextBox.Text));
+                d(this.OneWayBind(ViewModel, vm => vm.LoginButtonText, v => v.loginButton.Content));
+                d(this.OneWayBind(ViewModel, vm => vm.IsLoginInProgress, v => v.loginButton.IsEnabled, inProgress => !inProgress));
                 d(this.BindCommand(ViewModel, vm => vm.LoginCmd, v => v.loginButton));
             });