wpf: Add AutoFill to control whether the connection/buffer resizes (m…

…icrosoft#7853)

Adds the ability to manually handle the terminal renderer resizing
events by allowing different render size and WPF control size. This is
done by adding an `AutoFill` property to the control that prevents the
renderer from automatically resizing and tells the WPF control to fill
in the extra space with the terminal background as shown below:

This PR adds the following:
- Helper method in the DX engine to convert character viewports into
  pixel viewports
- `AutoFill` property that prevents automatic resizing of the renderer
- Tweaks and fixes that automatically fill in the empty space if
  `AutoFill` is set to false
- Fixes resizing methods and streamlines their codepath

## Validation Steps Performed
Manual validation with the Visual Studio Integrated Terminal tool
window.

src/cascadia/PublicTerminalCore/HwndTerminal.cpp

@@ -433,7 +433,15 @@ void _stdcall TerminalSendOutput(void* terminal, LPCWSTR data)
     publicTerminal->SendOutput(data);
 }
 
-HRESULT _stdcall TerminalTriggerResize(void* terminal, double width, double height, _Out_ COORD* dimensions)
+/// <summary>
+/// Triggers a terminal resize using the new width and height in pixel.
+/// </summary>
+/// <param name="terminal">Terminal pointer.</param>
+/// <param name="width">New width of the terminal in pixels.</param>
+/// <param name="height">New height of the terminal in pixels</param>
+/// <param name="dimensions">Out parameter containing the columns and rows that fit the new size.</param>
+/// <returns>HRESULT of the attempted resize.</returns>
+HRESULT _stdcall TerminalTriggerResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions)
 {
     const auto publicTerminal = static_cast<HwndTerminal*>(terminal);
 
@@ -446,10 +454,55 @@ HRESULT _stdcall TerminalTriggerResize(void* terminal, double width, double heig
         static_cast<int>(height),
         0));
 
-    const SIZE windowSize{ static_cast<short>(width), static_cast<short>(height) };
+    const SIZE windowSize{ width, height };
     return publicTerminal->Refresh(windowSize, dimensions);
 }
 
+/// <summary>
+/// Helper method for resizing the terminal using character column and row counts
+/// </summary>
+/// <param name="terminal">Pointer to the terminal object.</param>
+/// <param name="dimensionsInCharacters">New terminal size in row and column count.</param>
+/// <param name="dimensionsInPixels">Out parameter with the new size of the renderer.</param>
+/// <returns>HRESULT of the attempted resize.</returns>
+HRESULT _stdcall TerminalTriggerResizeWithDimension(_In_ void* terminal, _In_ COORD dimensionsInCharacters, _Out_ SIZE* dimensionsInPixels)
+{
+    RETURN_HR_IF_NULL(E_INVALIDARG, dimensionsInPixels);
+
+    const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);
+
+    const auto viewInCharacters = Viewport::FromDimensions({ 0, 0 }, { (dimensionsInCharacters.X), (dimensionsInCharacters.Y) });
+    const auto viewInPixels = publicTerminal->_renderEngine->GetViewportInPixels(viewInCharacters);
+
+    dimensionsInPixels->cx = viewInPixels.Width();
+    dimensionsInPixels->cy = viewInPixels.Height();
+
+    COORD unused{ 0, 0 };
+
+    return TerminalTriggerResize(terminal, viewInPixels.Width(), viewInPixels.Height(), &unused);
+}
+
+/// <summary>
+/// Calculates the amount of rows and columns that fit in the provided width and height.
+/// </summary>
+/// <param name="terminal">Terminal pointer</param>
+/// <param name="width">Width of the terminal area to calculate.</param>
+/// <param name="height">Height of the terminal area to calculate.</param>
+/// <param name="dimensions">Out parameter containing the columns and rows that fit the new size.</param>
+/// <returns>HRESULT of the calculation.</returns>
+HRESULT _stdcall TerminalCalculateResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions)
+{
+    const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);
+
+    const auto viewInPixels = Viewport::FromDimensions({ 0, 0 }, { width, height });
+    const auto viewInCharacters = publicTerminal->_renderEngine->GetViewportInCharacters(viewInPixels);
+
+    dimensions->X = viewInCharacters.Width();
+    dimensions->Y = viewInCharacters.Height();
+
+    return S_OK;
+}
+
 void _stdcall TerminalDpiChanged(void* terminal, int newDpi)
 {
     const auto publicTerminal = static_cast<HwndTerminal*>(terminal);
@@ -760,18 +813,6 @@ void _stdcall TerminalSetTheme(void* terminal, TerminalTheme theme, LPCWSTR font
     publicTerminal->Refresh(windowSize, &dimensions);
 }
 
-// Resizes the terminal to the specified rows and columns.
-HRESULT _stdcall TerminalResize(void* terminal, COORD dimensions)
-{
-    const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);
-
-    auto lock = publicTerminal->_terminal->LockForWriting();
-    publicTerminal->_terminal->ClearSelection();
-    publicTerminal->_renderer->TriggerRedrawAll();
-
-    return publicTerminal->_terminal->UserResize(dimensions);
-}
-
 void _stdcall TerminalBlinkCursor(void* terminal)
 {
     const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);

src/cascadia/PublicTerminalCore/HwndTerminal.hpp

@@ -27,8 +27,9 @@ extern "C" {
 __declspec(dllexport) HRESULT _stdcall CreateTerminal(HWND parentHwnd, _Out_ void** hwnd, _Out_ void** terminal);
 __declspec(dllexport) void _stdcall TerminalSendOutput(void* terminal, LPCWSTR data);
 __declspec(dllexport) void _stdcall TerminalRegisterScrollCallback(void* terminal, void __stdcall callback(int, int, int));
-__declspec(dllexport) HRESULT _stdcall TerminalTriggerResize(void* terminal, double width, double height, _Out_ COORD* dimensions);
-__declspec(dllexport) HRESULT _stdcall TerminalResize(void* terminal, COORD dimensions);
+__declspec(dllexport) HRESULT _stdcall TerminalTriggerResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions);
+__declspec(dllexport) HRESULT _stdcall TerminalTriggerResizeWithDimension(_In_ void* terminal, _In_ COORD dimensions, _Out_ SIZE* dimensionsInPixels);
+__declspec(dllexport) HRESULT _stdcall TerminalCalculateResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions);
 __declspec(dllexport) void _stdcall TerminalDpiChanged(void* terminal, int newDpi);
 __declspec(dllexport) void _stdcall TerminalUserScroll(void* terminal, int viewTop);
 __declspec(dllexport) void _stdcall TerminalClearSelection(void* terminal);
@@ -90,7 +91,9 @@ struct HwndTerminal : ::Microsoft::Console::Types::IControlAccessibilityInfo
     std::optional<til::point> _singleClickTouchdownPos;
 
     friend HRESULT _stdcall CreateTerminal(HWND parentHwnd, _Out_ void** hwnd, _Out_ void** terminal);
-    friend HRESULT _stdcall TerminalResize(void* terminal, COORD dimensions);
+    friend HRESULT _stdcall TerminalTriggerResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions);
+    friend HRESULT _stdcall TerminalTriggerResizeWithDimension(_In_ void* terminal, _In_ COORD dimensions, _Out_ SIZE* dimensionsInPixels);
+    friend HRESULT _stdcall TerminalCalculateResize(_In_ void* terminal, _In_ short width, _In_ short height, _Out_ COORD* dimensions);
     friend void _stdcall TerminalDpiChanged(void* terminal, int newDpi);
     friend void _stdcall TerminalUserScroll(void* terminal, int viewTop);
     friend void _stdcall TerminalClearSelection(void* terminal);

src/cascadia/WpfTerminalControl/NativeMethods.cs

@@ -7,7 +7,6 @@ namespace Microsoft.Terminal.Wpf
 {
     using System;
     using System.Runtime.InteropServices;
-    using System.Windows.Automation.Provider;
 
 #pragma warning disable SA1600 // Elements should be documented
     internal static class NativeMethods
@@ -187,10 +186,13 @@ public enum SetWindowPosFlags : uint
         public static extern void TerminalSendOutput(IntPtr terminal, string lpdata);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
-        public static extern uint TerminalTriggerResize(IntPtr terminal, double width, double height, out COORD dimensions);
+        public static extern uint TerminalTriggerResize(IntPtr terminal, short width, short height, out COORD dimensions);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
-        public static extern uint TerminalResize(IntPtr terminal, COORD dimensions);
+        public static extern uint TerminalTriggerResizeWithDimension(IntPtr terminal, [MarshalAs(UnmanagedType.Struct)] COORD dimensions, out SIZE dimensionsInPixels);
+
+        [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
+        public static extern uint TerminalCalculateResize(IntPtr terminal, short width, short height, out COORD dimensions);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
         public static extern void TerminalDpiChanged(IntPtr terminal, int newDpi);
@@ -205,10 +207,10 @@ public enum SetWindowPosFlags : uint
         public static extern void TerminalUserScroll(IntPtr terminal, int viewTop);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
-        public static extern uint TerminalStartSelection(IntPtr terminal, NativeMethods.COORD cursorPosition, bool altPressed);
+        public static extern uint TerminalStartSelection(IntPtr terminal, COORD cursorPosition, bool altPressed);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
-        public static extern uint TerminalMoveSelection(IntPtr terminal, NativeMethods.COORD cursorPosition);
+        public static extern uint TerminalMoveSelection(IntPtr terminal, COORD cursorPosition);
 
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
         public static extern void TerminalClearSelection(IntPtr terminal);
@@ -278,10 +280,24 @@ public struct COORD
             public short X;
 
             /// <summary>
-            /// The x-coordinate of the point.
+            /// The y-coordinate of the point.
             /// </summary>
             public short Y;
         }
+
+        [StructLayout(LayoutKind.Sequential)]
+        public struct SIZE
+        {
+            /// <summary>
+            ///  The x size.
+            /// </summary>
+            public int cx;
+
+            /// <summary>
+            /// The y size.
+            /// </summary>
+            public int cy;
+        }
     }
 #pragma warning restore SA1600 // Elements should be documented
 }

src/cascadia/WpfTerminalControl/TerminalContainer.cs

@@ -20,20 +20,6 @@ namespace Microsoft.Terminal.Wpf
     /// </remarks>
     public class TerminalContainer : HwndHost
     {
-        private static void UnpackKeyMessage(IntPtr wParam, IntPtr lParam, out ushort vkey, out ushort scanCode, out ushort flags)
-        {
-            ulong scanCodeAndFlags = (((ulong)lParam) & 0xFFFF0000) >> 16;
-            scanCode = (ushort)(scanCodeAndFlags & 0x00FFu);
-            flags = (ushort)(scanCodeAndFlags & 0xFF00u);
-            vkey = (ushort)wParam;
-        }
-
-        private static void UnpackCharMessage(IntPtr wParam, IntPtr lParam, out char character, out ushort scanCode, out ushort flags)
-        {
-            UnpackKeyMessage(wParam, lParam, out ushort vKey, out scanCode, out flags);
-            character = (char)vKey;
-        }
-
         private ITerminalConnection connection;
         private IntPtr hwnd;
         private IntPtr terminal;
@@ -77,15 +63,33 @@ public TerminalContainer()
         internal event EventHandler<int> UserScrolled;
 
         /// <summary>
-        /// Gets the character rows available to the terminal.
+        /// Gets or sets a value indicating whether if the renderer should automatically resize to fill the control
+        /// on user action.
+        /// </summary>
+        public bool AutoFill { get; set; } = true;
+
+        /// <summary>
+        /// Gets the current character rows available to the terminal.
         /// </summary>
         internal int Rows { get; private set; }
 
         /// <summary>
-        /// Gets the character columns available to the terminal.
+        /// Gets the current character columns available to the terminal.
         /// </summary>
         internal int Columns { get; private set; }
 
+        /// <summary>
+        /// Gets the maximum amount of character rows that can fit in this control.
+        /// </summary>
+        /// <remarks>This will be in sync with <see cref="Rows"/> unless <see cref="AutoFill"/> is set to false.</remarks>
+        internal int MaxRows { get; private set; }
+
+        /// <summary>
+        /// Gets the maximum amount of character columns that can fit in this control.
+        /// </summary>
+        /// <remarks>This will be in sync with <see cref="Columns"/> unless <see cref="AutoFill"/> is set to false.</remarks>
+        internal int MaxColumns { get; private set; }
+
         /// <summary>
         /// Gets the window handle of the terminal.
         /// </summary>
@@ -162,34 +166,50 @@ internal string GetSelectedText()
             var dpiScale = VisualTreeHelper.GetDpi(this);
 
             NativeMethods.COORD dimensions;
-            NativeMethods.TerminalTriggerResize(this.terminal, renderSize.Width * dpiScale.DpiScaleX, renderSize.Height * dpiScale.DpiScaleY, out dimensions);
+            NativeMethods.TerminalTriggerResize(
+                this.terminal,
+                Convert.ToInt16(renderSize.Width * dpiScale.DpiScaleX),
+                Convert.ToInt16(renderSize.Height * dpiScale.DpiScaleY),
+                out dimensions);
 
             this.Rows = dimensions.Y;
             this.Columns = dimensions.X;
 
-            this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+            this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
             return (dimensions.Y, dimensions.X);
         }
 
         /// <summary>
-        /// Resizes the terminal.
+        /// Resizes the terminal using row and column count as the new size.
         /// </summary>
         /// <param name="rows">Number of rows to show.</param>
         /// <param name="columns">Number of columns to show.</param>
-        internal void Resize(uint rows, uint columns)
+        /// <returns><see cref="long"/> pair with the new width and height size in pixels for the renderer.</returns>
+        internal (int width, int height) Resize(uint rows, uint columns)
         {
+            NativeMethods.SIZE dimensionsInPixels;
             NativeMethods.COORD dimensions = new NativeMethods.COORD
             {
                 X = (short)columns,
                 Y = (short)rows,
             };
 
-            NativeMethods.TerminalResize(this.terminal, dimensions);
+            NativeMethods.TerminalTriggerResizeWithDimension(this.terminal, dimensions, out dimensionsInPixels);
+
+            // If AutoFill is true, keep Rows and Columns in sync with MaxRows and MaxColumns.
+            // Otherwise, MaxRows and MaxColumns will be set on startup and on control resize by the user.
+            if (this.AutoFill)
+            {
+                this.MaxColumns = dimensions.X;
+                this.MaxRows = dimensions.Y;
+            }
 
-            this.Rows = dimensions.Y;
             this.Columns = dimensions.X;
+            this.Rows = dimensions.Y;
 
-            this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+            this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+
+            return (dimensionsInPixels.cx, dimensionsInPixels.cy);
         }
 
         /// <inheritdoc/>
@@ -238,6 +258,20 @@ protected override void DestroyWindowCore(HandleRef hwnd)
             this.terminal = IntPtr.Zero;
         }
 
+        private static void UnpackKeyMessage(IntPtr wParam, IntPtr lParam, out ushort vkey, out ushort scanCode, out ushort flags)
+        {
+            ulong scanCodeAndFlags = (((ulong)lParam) & 0xFFFF0000) >> 16;
+            scanCode = (ushort)(scanCodeAndFlags & 0x00FFu);
+            flags = (ushort)(scanCodeAndFlags & 0xFF00u);
+            vkey = (ushort)wParam;
+        }
+
+        private static void UnpackCharMessage(IntPtr wParam, IntPtr lParam, out char character, out ushort scanCode, out ushort flags)
+        {
+            UnpackKeyMessage(wParam, lParam, out ushort vKey, out scanCode, out flags);
+            character = (char)vKey;
+        }
+
         private void TerminalContainer_GotFocus(object sender, RoutedEventArgs e)
         {
             e.Handled = true;
@@ -299,13 +333,28 @@ private IntPtr TerminalContainer_MessageHook(IntPtr hwnd, int msg, IntPtr wParam
                             break;
                         }
 
-                        NativeMethods.TerminalTriggerResize(this.terminal, windowpos.cx, windowpos.cy, out var dimensions);
+                        NativeMethods.COORD dimensions;
 
-                        this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
-                        this.Columns = dimensions.X;
-                        this.Rows = dimensions.Y;
+                        // We only trigger a resize if we want to fill to maximum size.
+                        if (this.AutoFill)
+                        {
+                            NativeMethods.TerminalTriggerResize(this.terminal, (short)windowpos.cx, (short)windowpos.cy, out dimensions);
+
+                            this.Columns = dimensions.X;
+                            this.Rows = dimensions.Y;
+                            this.MaxColumns = dimensions.X;
+                            this.MaxRows = dimensions.Y;
+                        }
+                        else
+                        {
+                            NativeMethods.TerminalCalculateResize(this.terminal, (short)windowpos.cx, (short)windowpos.cy, out dimensions);
+                            this.MaxColumns = dimensions.X;
+                            this.MaxRows = dimensions.Y;
+                        }
 
+                        this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
                         break;
+
                     case NativeMethods.WindowMessage.WM_MOUSEWHEEL:
                         var delta = (short)(((long)wParam) >> 16);
                         this.UserScrolled?.Invoke(this, delta);
@@ -360,7 +409,7 @@ private void OnScroll(int viewTop, int viewHeight, int bufferSize)
 
         private void OnWrite(string data)
         {
-            this.connection?.WriteInput(data);
+            this.Connection?.WriteInput(data);
         }
     }
 }

src/cascadia/WpfTerminalControl/TerminalControl.xaml

@@ -6,8 +6,9 @@
              xmlns:local="clr-namespace:Microsoft.Terminal.Wpf"
              mc:Ignorable="d" 
              d:DesignHeight="450" d:DesignWidth="800"
-             Focusable="True">
-    <Grid>
+             Focusable="True"
+             x:Name="terminalUserControl">
+    <Grid x:Name="terminalGrid">
         <Grid.ColumnDefinitions>
             <ColumnDefinition />
             <ColumnDefinition Width="Auto"/>