wpf: make the cursor blink (#3415)

src/cascadia/PublicTerminalCore/HwndTerminal.cpp

@@ -396,3 +396,20 @@ HRESULT _stdcall TerminalResize(void* terminal, COORD dimensions)
 
     return publicTerminal->_terminal->UserResize(dimensions);
 }
+
+void _stdcall TerminalBlinkCursor(void* terminal)
+{
+    const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);
+    if (!publicTerminal->_terminal->IsCursorBlinkingAllowed() && publicTerminal->_terminal->IsCursorVisible())
+    {
+        return;
+    }
+
+    publicTerminal->_terminal->SetCursorVisible(!publicTerminal->_terminal->IsCursorVisible());
+}
+
+void _stdcall TerminalSetCursorVisible(void* terminal, const bool visible)
+{
+    const auto publicTerminal = static_cast<const HwndTerminal*>(terminal);
+    publicTerminal->_terminal->SetCursorVisible(visible);
+}

src/cascadia/PublicTerminalCore/HwndTerminal.hpp

@@ -35,6 +35,8 @@ __declspec(dllexport) void _stdcall TerminalSetTheme(void* terminal, TerminalThe
 __declspec(dllexport) void _stdcall TerminalRegisterWriteCallback(void* terminal, const void __stdcall callback(wchar_t*));
 __declspec(dllexport) void _stdcall TerminalSendKeyEvent(void* terminal, WPARAM wParam);
 __declspec(dllexport) void _stdcall TerminalSendCharEvent(void* terminal, wchar_t ch);
+__declspec(dllexport) void _stdcall TerminalBlinkCursor(void* terminal);
+__declspec(dllexport) void _stdcall TerminalSetCursorVisible(void* terminal, const bool visible);
 };
 
 struct HwndTerminal
@@ -69,5 +71,7 @@ private:
     friend void _stdcall TerminalSendKeyEvent(void* terminal, WPARAM wParam);
     friend void _stdcall TerminalSendCharEvent(void* terminal, wchar_t ch);
     friend void _stdcall TerminalSetTheme(void* terminal, TerminalTheme theme, LPCWSTR fontFamily, short fontSize, int newDpi);
+    friend void _stdcall TerminalBlinkCursor(void* terminal);
+    friend void _stdcall TerminalSetCursorVisible(void* terminal, const bool visible);
     void _UpdateFont(int newDpi);
 };

src/cascadia/WpfTerminalControl/NativeMethods.cs

@@ -21,6 +21,16 @@ namespace Microsoft.Terminal.Wpf
 
         public enum WindowMessage : int
         {
+            /// <summary>
+            /// The WM_SETFOCUS message is sent to a window after it has gained the keyboard focus.
+            /// </summary>
+            WM_SETFOCUS = 0x0007,
+
+            /// <summary>
+            /// The WM_KILLFOCUS message is sent to a window immediately before it loses the keyboard focus.
+            /// </summary>
+            WM_KILLFOCUS = 0x0008,
+
             /// <summary>
             /// The WM_MOUSEACTIVATE message is sent when the cursor is in an inactive window and the user presses a mouse button. The parent window receives this message only if the child window passes it to the DefWindowProc function.
             /// </summary>
@@ -202,12 +212,24 @@ namespace Microsoft.Terminal.Wpf
         [DllImport("PublicTerminalCore.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall)]
         public static extern void TerminalSetTheme(IntPtr terminal, [MarshalAs(UnmanagedType.Struct)] TerminalTheme theme, string fontFamily, short fontSize, int newDpi);
 
+        [DllImport("PublicTerminalCore.dll", CallingConvention = CallingConvention.StdCall)]
+        public static extern void TerminalBlinkCursor(IntPtr terminal);
+
+        [DllImport("PublicTerminalCore.dll", CallingConvention = CallingConvention.StdCall)]
+        public static extern void TerminalSetCursorVisible(IntPtr terminal, bool visible);
+
         [DllImport("user32.dll", SetLastError = true)]
         public static extern IntPtr SetFocus(IntPtr hWnd);
 
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern IntPtr GetFocus();
+
         [DllImport("user32.dll", SetLastError = true)]
         public static extern short GetKeyState(int keyCode);
 
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern uint GetCaretBlinkTime();
+
         [StructLayout(LayoutKind.Sequential)]
         public struct WINDOWPOS
         {

src/cascadia/WpfTerminalControl/TerminalContainer.cs

@@ -10,6 +10,7 @@ namespace Microsoft.Terminal.Wpf
     using System.Windows;
     using System.Windows.Interop;
     using System.Windows.Media;
+    using System.Windows.Threading;
 
     /// <summary>
     /// The container class that hosts the native hwnd terminal.
@@ -22,7 +23,7 @@ namespace Microsoft.Terminal.Wpf
         private ITerminalConnection connection;
         private IntPtr hwnd;
         private IntPtr terminal;
-
+        private DispatcherTimer blinkTimer;
         private NativeMethods.ScrollCallback scrollCallback;
         private NativeMethods.WriteCallback writeCallback;
 
@@ -34,6 +35,21 @@ namespace Microsoft.Terminal.Wpf
             this.MessageHook += this.TerminalContainer_MessageHook;
             this.GotFocus += this.TerminalContainer_GotFocus;
             this.Focusable = true;
+
+            var blinkTime = NativeMethods.GetCaretBlinkTime();
+
+            if (blinkTime != uint.MaxValue)
+            {
+                this.blinkTimer = new DispatcherTimer();
+                this.blinkTimer.Interval = TimeSpan.FromMilliseconds(blinkTime);
+                this.blinkTimer.Tick += (_, __) =>
+                {
+                    if (this.terminal != IntPtr.Zero)
+                    {
+                        NativeMethods.TerminalBlinkCursor(this.terminal);
+                    }
+                };
+            }
         }
 
         /// <summary>
@@ -171,6 +187,15 @@ namespace Microsoft.Terminal.Wpf
                 NativeMethods.TerminalDpiChanged(this.terminal, (int)dpiScale.PixelsPerInchX);
             }
 
+            if (NativeMethods.GetFocus() == this.hwnd)
+            {
+                this.blinkTimer?.Start();
+            }
+            else
+            {
+                NativeMethods.TerminalSetCursorVisible(this.terminal, false);
+            }
+
             return new HandleRef(this, this.hwnd);
         }
 
@@ -193,6 +218,13 @@ namespace Microsoft.Terminal.Wpf
             {
                 switch ((NativeMethods.WindowMessage)msg)
                 {
+                    case NativeMethods.WindowMessage.WM_SETFOCUS:
+                        this.blinkTimer?.Start();
+                        break;
+                    case NativeMethods.WindowMessage.WM_KILLFOCUS:
+                        this.blinkTimer?.Stop();
+                        NativeMethods.TerminalSetCursorVisible(this.terminal, false);
+                        break;
                     case NativeMethods.WindowMessage.WM_MOUSEACTIVATE:
                         this.Focus();
                         NativeMethods.SetFocus(this.hwnd);
@@ -215,8 +247,10 @@ namespace Microsoft.Terminal.Wpf
                         this.MouseMoveHandler((int)wParam, (int)lParam);
                         break;
                     case NativeMethods.WindowMessage.WM_KEYDOWN:
+                        NativeMethods.TerminalSetCursorVisible(this.terminal, true);
                         NativeMethods.TerminalClearSelection(this.terminal);
                         NativeMethods.TerminalSendKeyEvent(this.terminal, wParam);
+                        this.blinkTimer?.Start();
                         break;
                     case NativeMethods.WindowMessage.WM_CHAR:
                         NativeMethods.TerminalSendCharEvent(this.terminal, (char)wParam);