Grid: RowDefinition and ColumnDefinition Constructor changes

active/RowColumnAPIChange/rowcolumnapichange.md

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+
+<!-- The purpose of this spec is to describe a new feature and
+its APIs that make up a new feature in WinUI. -->
+
+<!-- There are two audiences for the spec. The first are people
+that want to evaluate and give feedback on the API, as part of
+the submission process.  When it's complete
+it will be incorporated into the public documentation at
+docs.microsoft.com (http://docs.microsoft.com/uwp/toolkits/winui/).
+Hopefully we'll be able to copy it mostly verbatim.
+So the second audience is everyone that reads there to learn how
+and why to use this API. -->
+
+# Background
+<!-- Use this section to provide background context for the new API(s) 
+in this spec. -->
+
+<!-- This section and the appendix are the only sections that likely
+do not get copied to docs.microsoft.com; they're just an aid to reading this spec. -->
+
+<!-- If you're modifying an existing API, included a link here to the
+existing page(s) -->
+
+<!-- For example, this section is a place to explain why you're adding this API rather than
+modifying an existing API. -->
+
+<!-- For example, this is a place to provide a brief explanation of some dependent
+area, just explanation enough to understand this new API, rather than telling
+the reader "go read 100 pages of background information posted at ...". -->
+
+[Grid](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.grid?view=winrt-18362) has ColumnDefinitions and RowDefinitions properties. The values for these properties are a collection of [ColumnDefinition](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.columndefinition?view=winrt-18362) and [RowDefinition](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.rowdefinition?view=winrt-18362) objects, respectively. Currently, RowDefinition and ColumnDefinition constructors do not take any arguments. Due to this, defining a ColumnDefinition or RowDefinition can be lengthy and unintuitive, with the steps as follows:
+1. Create a Column or RowDefinition object with the blank constructor.
+2. Define a GridLength object with the desired value for the Height or Width property of the Row/ColumnDefinition.
+3. Assign the GridLength object to the Height or Width property of the Row/ColumnDefinition. 
+
+This spec sets out to change that process, and therefore sets out to change the [RowDefinition](https://docs.microsoft.com/uwp/api/Windows.UI.Xaml.Controls.RowDefinition) and [ColumnDefinition](https://docs.microsoft.com/uwp/api/windows.ui.xaml.controls.columndefinition) APIs.
+
+This new feature will allow developers to define their column widths and row heights within the column and row definitions themselves, not only making the code-behind easier to write, but making it cleaner and more understandable to read as well. 
+
+# Description
+<!-- Use this section to provide a brief description of the feature.
+For an example, see the introduction to the PasswordBox control 
+(http://docs.microsoft.com/windows/uwp/design/controls-and-patterns/password-box). -->
+
+ColumnDefinition and RowDefinition constructors will be overloaded to take in one or two arguments. The first overloaded constructor for `ColumnDefinition()` will take only a double-type argument called Width (Height for `RowDefinition()`). The second overloaded constructor for ColumnDefinition() will take a double-type argument Width (Height for RowDefinition()) and a [GridUnitType](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.gridlength.gridunittype) argument.
+
+These overloaded constructors take the same arguments as the [GridLength](https://docs.microsoft.com/en-us/uwp/api/Windows.UI.Xaml.GridLength) constructor does - a double and a GridUnitType. In turn, feeding these same arguments to a RowDefinition or ColumnDefinition constructor will create a GridLength object and assign it to the ColumnDefinition's Width property or the RowDefinition's Height property behind the scenes. 
+
+# Examples
+<!-- Use this section to explain the features of the API, showing
+example code with each description. The general format is: 
+  feature explanation,
+  example code
+  feature explanation,
+  example code
+  etc.-->
+
+<!-- Code samples should be in C# and/or C++/WinRT -->
+
+<!-- As an example of this section, see the Examples section for the PasswordBox control 
+(https://docs.microsoft.com/windows/uwp/design/controls-and-patterns/password-box#examples). -->
+Current syntax to define a Grid with one column in code-behind:
+```csharp
+var grid = new Grid();
+var column = new ColumnDefinition();
+column.Width = new GridLength(1.0, GridUnitType.Star);
+grid.ColumnDefinitions.Add(column);
+```
+
+or
+
+```csharp
+var column = new ColumnDefinition
+{
+    Width = new GridLength(1.0, GridUnitType.Star)
+};
+```
+
+
+New syntax to define a Grid with one column in code-behind:
+```csharp
+var grid = new Grid();
+grid.ColumnDefinitions.Add(new ColumnDefinition(1.0, GridUnitType.Star)); // Width="1*"
+```
+
+New syntax to define a Grid with one simple column in code-behind, where the GridUnitType is a pixel:
+```csharp
+grid.ColumnDefinitions.Add(new ColumnDefinition(500.0)); // Width="500px"
+```
+
+<!-- # Remarks -->
+<!-- Explanation and guidance that doesn't fit into the Examples section. -->
+
+<!-- APIs should only throw exceptions in exceptional conditions; basically,
+only when there's a bug in the caller, such as argument exception.  But if for some
+reason it's necessary for a caller to catch an exception from an API, call that
+out with an explanation either here or in the Examples -->
+If defining a column or row with a GridUnitType of Auto, the value in the Width/Height parameter should be ignored - Auto should override the specified Width/Height value. 
+
+For ColumnDefinitions or RowDefinitions that have `NaN` as their value for Height or Width in their constructor, an error should be thrown.
+
+
+# API Notes
+ColumnDefinition constructor will be overloaded to take a double `pixelWidth` OR take two arguments consisting of a double `width` and a GridUnitType `type`:
+
+```csharp
+public ColumnDefinition(double pixelWidth) { ... }
+```
+
+```csharp
+public ColumnDefinition(double width, GridUnitType type) { ... }
+```
+
+RowDefinition constructor will be overloaded to take a double `pixelHeight` OR take two arguments consisting of a double `height` and a GridUnitType `type`:
+
+```csharp
+public RowDefinition(double pixelHeight) { ... }
+```
+
+```csharp
+public RowDefinition(double height, GridUnitType type) { ... }
+```
+
+# API Details
+```csharp
+//RowDefinition API:
+[contract(Windows.Foundation.UniversalApiContract, 1)]
+[webhosthidden]
+[static_name("Windows.UI.Xaml.Controls.IRowDefinitionStatics", 5adf3fe5-2056-4724-94d6-e4812b022ec8)]
+[interface_name("Windows.UI.Xaml.Controls.IRowDefinition", 4abae829-d80c-4a5e-a48c-f8b3d3b6533d)]
+runtimeclass RowDefinition
+    : Windows.UI.Xaml.DependencyObject
+{
+    // vvvv
+    RowDefinition(double height, GridUnitType type);
+    RowDefinition(double pixelHeight);
+    // ^^^^
+    Windows.UI.Xaml.GridLength Height;
+    Double MaxHeight;
+    Double MinHeight;
+    Double ActualHeight{ get; };
+    static Windows.UI.Xaml.DependencyProperty HeightProperty{ get; };
+    static Windows.UI.Xaml.DependencyProperty MaxHeightProperty{ get; };
+    static Windows.UI.Xaml.DependencyProperty MinHeightProperty{ get; };
+};
+
+//ColumnDefinition API:
+[contract(Windows.Foundation.UniversalApiContract, 1)]
+[webhosthidden]
+[static_name("Windows.UI.Xaml.Controls.IColumnDefinitionStatics", 06b0d728-d044-40c6-942e-ae60eac74851)]
+[interface_name("Windows.UI.Xaml.Controls.IColumnDefinition", f7f1b229-f024-467f-970a-7e705615db7b)]
+runtimeclass ColumnDefinition
+    : Windows.UI.Xaml.DependencyObject
+{
+    // vvvv
+    ColumnDefinition(double width, GridUnitType type);
+    ColumnDefinition(double pixelWidth);
+    // ^^^^
+    Windows.UI.Xaml.GridLength Width;
+    Double MaxWidth;
+    Double MinWidth;
+    Double ActualWidth{ get; };
+    static Windows.UI.Xaml.DependencyProperty WidthProperty{ get; };
+    static Windows.UI.Xaml.DependencyProperty MaxWidthProperty{ get; };
+    static Windows.UI.Xaml.DependencyProperty MinWidthProperty{ get; };
+};
+```
+
+<!-- # Appendix -->
+<!-- Anything else that you want to write down for posterity, but 
+that isn't necessary to understand the purpose and usage of the API.
+For example, implementation details. -->