Get rid of the padding above the tab row when maximized (#5881)

## Summary of the Pull Request

When we maximize the window, shrink the caption buttons (the min, max, close buttons) down to 32px tall, to be the same height as the `TabRowControl`. This way, the tabs will be flush with the top of the display.

## PR Checklist
* [x] Closes #2541
* [x] I work here
* [ ] Tests added/passed
* [n/a] Requires documentation to be updated

## Detailed Description of the Pull Request / Additional comments

I tried for a couple hours this morning to do this as a `VisualState`. First I tried doing it as one on the TabRow, which I had very little success with. Then, I eventually realized that the TabRow wasn't even responsible for the padding there, it was being created by the fact that the caption buttons were too tall. Again, I tried to use the existing `VisualState`s they have defined for this, but I couldn't figure out how to do that.

I think the visual state solution would be _cleaner_, so if someone knows how to do that instead, please let me know. 

## Validation Steps Performed

* Maximized/restored the Terminal on my display with the taskbar on the bottom
* Maximized/restored the Terminal on my display with the taskbar on the top

Author: zadjii-msft

src/cascadia/TerminalApp/MinMaxCloseControl.cpp

@@ -40,15 +40,53 @@ namespace winrt::TerminalApp::implementation
 
     void MinMaxCloseControl::SetWindowVisualState(WindowVisualState visualState)
     {
+        // Look up the heights we should use for the caption buttons from our
+        // XAML resources. "CaptionButtonHeightWindowed" and
+        // "CaptionButtonHeightMaximized" define the size we should use for the
+        // caption buttons height for the windowed and maximized states,
+        // respectively.
+        //
+        // use C++11 magic statics to make sure we only do this once.
+        static auto heights = [this]() {
+            const auto res = Resources();
+            const auto windowedHeightKey = winrt::box_value(L"CaptionButtonHeightWindowed");
+            const auto maximizedHeightKey = winrt::box_value(L"CaptionButtonHeightMaximized");
+
+            auto windowedHeight = 0.0;
+            auto maximizedHeight = 0.0;
+            if (res.HasKey(windowedHeightKey))
+            {
+                const auto valFromResources = res.Lookup(windowedHeightKey);
+                windowedHeight = winrt::unbox_value_or<double>(valFromResources, 0.0);
+            }
+            if (res.HasKey(maximizedHeightKey))
+            {
+                const auto valFromResources = res.Lookup(maximizedHeightKey);
+                maximizedHeight = winrt::unbox_value_or<double>(valFromResources, 0.0);
+            }
+            return std::tuple<double, double>{ windowedHeight, maximizedHeight };
+        }();
+        static const auto windowedHeight = std::get<0>(heights);
+        static const auto maximizedHeight = std::get<1>(heights);
+
         switch (visualState)
         {
         case WindowVisualState::WindowVisualStateMaximized:
-            winrt::Windows::UI::Xaml::VisualStateManager::GoToState(MaximizeButton(), L"WindowStateMaximized", false);
+            VisualStateManager::GoToState(MaximizeButton(), L"WindowStateMaximized", false);
+
+            MinimizeButton().Height(maximizedHeight);
+            MaximizeButton().Height(maximizedHeight);
+            CloseButton().Height(maximizedHeight);
             break;
+
         case WindowVisualState::WindowVisualStateNormal:
         case WindowVisualState::WindowVisualStateIconified:
         default:
-            winrt::Windows::UI::Xaml::VisualStateManager::GoToState(MaximizeButton(), L"WindowStateNormal", false);
+            VisualStateManager::GoToState(MaximizeButton(), L"WindowStateNormal", false);
+
+            MinimizeButton().Height(windowedHeight);
+            MaximizeButton().Height(windowedHeight);
+            CloseButton().Height(windowedHeight);
             break;
         }
     }

src/cascadia/TerminalApp/MinMaxCloseControl.xaml

@@ -62,13 +62,26 @@ the MIT License. See LICENSE in the project root for license information. -->
             <x:String x:Key="CaptionButtonPath"></x:String>
             <x:String x:Key="CaptionButtonPathWindowMaximized"></x:String>
 
+            <!-- "CaptionButtonHeightWindowed" and
+                 "CaptionButtonHeightMaximized" define the size we should use
+                 for the caption buttons height for the windowed and maximized
+                 states, respectively.
+
+                 32 was chosen for the Maximized height to match the height of
+                 the TabRowControl. This way, when the window is maximized, the
+                 tabs will be flush with the top of the window. See GH#2541 for
+                 details.-->
+            <x:Double x:Key="CaptionButtonHeightWindowed">36.0</x:Double>
+            <x:Double x:Key="CaptionButtonHeightMaximized">32.0</x:Double>
+
             <Style x:Key="CaptionButton" TargetType="Button">
                 <Setter Property="BorderThickness" Value="0"/>
                 <Setter Property="Background" Value="{ThemeResource CaptionButtonBackground}" />
                 <Setter Property="IsTabStop" Value="False" />
                 <Setter Property="Template">
                     <Setter.Value>
                         <ControlTemplate TargetType="Button">
+
                             <Border x:Name="ButtonBaseElement"
                                 Background="{TemplateBinding Background}"
                                 BackgroundSizing="{TemplateBinding BackgroundSizing}"
@@ -123,6 +136,7 @@ the MIT License. See LICENSE in the project root for license information. -->
                                     StrokeEndLineCap="Square"
                                     StrokeStartLineCap="Square" />
                             </Border>
+
                         </ControlTemplate>
                     </Setter.Value>
                 </Setter>
@@ -131,7 +145,7 @@ the MIT License. See LICENSE in the project root for license information. -->
         </ResourceDictionary>
     </StackPanel.Resources>
 
-    <Button Height="36.0" MinWidth="46.0" Width="46.0"
+    <Button Height="{StaticResource CaptionButtonHeightWindowed}" MinWidth="46.0" Width="46.0"
             x:Name="MinimizeButton"
             x:Uid="WindowMinimizeButton"
             Style="{StaticResource CaptionButton}"
@@ -143,7 +157,7 @@ the MIT License. See LICENSE in the project root for license information. -->
             </ResourceDictionary>
         </Button.Resources>
     </Button>
-    <Button Height="36.0" MinWidth="46.0" Width="46.0"
+    <Button Height="{StaticResource CaptionButtonHeightWindowed}" MinWidth="46.0" Width="46.0"
             x:Name="MaximizeButton"
             x:Uid="WindowMaximizeButton"
             Style="{StaticResource CaptionButton}"
@@ -156,7 +170,7 @@ the MIT License. See LICENSE in the project root for license information. -->
             </ResourceDictionary>
         </Button.Resources>
     </Button>
-    <Button Height="36.0" MinWidth="46.0" Width="46.0"
+    <Button Height="{StaticResource CaptionButtonHeightWindowed}" MinWidth="46.0" Width="46.0"
             x:Name="CloseButton"
             x:Uid="WindowCloseButton"
             Style="{StaticResource CaptionButton}"