add remarks about keyboard navigation (#3646)

Author: gewarren

xml/System.Windows.Forms/DataGridView.xml

@@ -3633,7 +3633,7 @@
 ## Remarks  
  The <xref:System.Windows.Forms.DataGridView.CellErrorTextNeeded> event occurs only when the <xref:System.Windows.Forms.DataGridView> control <xref:System.Windows.Forms.DataGridView.DataSource%2A> property is set or its <xref:System.Windows.Forms.DataGridView.VirtualMode%2A> property is `true`. Handling the <xref:System.Windows.Forms.DataGridView.CellErrorTextNeeded> event is useful when you want to determine the error for a cell depending on its value or state.  
 
- When you handle the <xref:System.Windows.Forms.DataGridView.CellErrorTextNeeded> event and specify error text in the handler, an error glyph appears in the cell unless the <xref:System.Windows.Forms.DataGridView.ShowCellErrors%2A> property is set to `false` or the cell is in edit mode. When the user moves the mouse pointer over the error glyph, the error text appears in a ToolTip.  
+ When you handle the <xref:System.Windows.Forms.DataGridView.CellErrorTextNeeded> event and specify error text in the handler, an error glyph appears in the cell unless the <xref:System.Windows.Forms.DataGridView.ShowCellErrors%2A> property is set to `false` or the cell is in edit mode. When the user moves the mouse pointer over the error glyph or navigates to the cell using the keyboard, the error text appears in a ToolTip.  
 
  The <xref:System.Windows.Forms.DataGridView.CellErrorTextNeeded> event also occurs whenever the value of the <xref:System.Windows.Forms.DataGridViewCell.ErrorText%2A?displayProperty=nameWithType> property is retrieved.  
 
@@ -4412,9 +4412,9 @@
 ## Remarks  
  The <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event occurs only when the <xref:System.Windows.Forms.DataGridView> control <xref:System.Windows.Forms.DataGridView.DataSource%2A> property is set or its <xref:System.Windows.Forms.DataGridView.VirtualMode%2A> property is `true`.  
 
- When you handle the <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event, the ToolTip text you specify in the handler is shown whenever the mouse pointer is over a cell and the control <xref:System.Windows.Forms.DataGridView.ShowCellToolTips%2A> property value is `true`. The <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event is useful when you want to display ToolTips determined by the current state or value of a cell.  
+ When you handle the <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event, the ToolTip text you specify in the handler is shown if the <xref:System.Windows.Forms.DataGridView.ShowCellToolTips%2A> property value is `true` and the mouse pointer is over the cell or the user navigates to the cell using the keyboard. The <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event is useful when you want to display ToolTips determined by the current state or value of a cell.  
 
- The <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event also occurs whenever the value of the <xref:System.Windows.Forms.DataGridViewCell.ToolTipText%2A?displayProperty=nameWithType> property is retrieved, either programmatically or when the mouse pointer enters a cell.  
+ The <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event also occurs whenever the value of the <xref:System.Windows.Forms.DataGridViewCell.ToolTipText%2A?displayProperty=nameWithType> property is retrieved, either programmatically or when the user navigates to the cell with the mouse or keyboard.  
 
  You can use the <xref:System.Windows.Forms.DataGridViewCellEventArgs.ColumnIndex%2A?displayProperty=nameWithType> and <xref:System.Windows.Forms.DataGridViewCellEventArgs.RowIndex%2A> properties to determine the state or value of a cell, and use this information to change or modify the <xref:System.Windows.Forms.DataGridViewCellToolTipTextNeededEventArgs.ToolTipText%2A?displayProperty=nameWithType> property. This property is initialized with the value of the cell <xref:System.Windows.Forms.DataGridViewCell.ToolTipText%2A> property, which the event value overrides.  
 
@@ -18193,14 +18193,14 @@ if (rowToDelete > -1)
         <ReturnType>System.Boolean</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets or sets a value indicating whether or not ToolTips will show when the mouse pointer pauses on a cell.</summary>
+        <summary>Gets or sets a value indicating whether or not ToolTips will show when the mouse pointer pauses on a cell or the user navigates to the cell using the keyboard.</summary>
         <value>
           <see langword="true" /> if cell ToolTips are enabled; otherwise, <see langword="false" />.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
 ## Remarks  
- When the value of this property is `true` and the mouse pointer is over a cell, the cell displays a ToolTip when one of the following conditions is met:  
+ When the value of this property is `true` and the mouse pointer is over a cell or the user has navigated to the cell using the keyboard, the cell displays a ToolTip when one of the following conditions is met:  
 
 -   The value of the <xref:System.Windows.Forms.DataGridView.DataSource%2A> property is not `null` or the value of the <xref:System.Windows.Forms.DataGridView.VirtualMode%2A> property is `true`, and a handler for the <xref:System.Windows.Forms.DataGridView.CellToolTipTextNeeded> event sets the <xref:System.Windows.Forms.DataGridViewCellToolTipTextNeededEventArgs.ToolTipText%2A?displayProperty=nameWithType> property to a value other than <xref:System.String.Empty?displayProperty=nameWithType>.