Add support for XTerm's NumLock mode

src/terminal/adapter/DispatchTypes.hpp

@@ -542,6 +542,7 @@ namespace Microsoft::Console::VirtualTerminal::DispatchTypes
         UTF8_EXTENDED_MODE = DECPrivateMode(1005),
         SGR_EXTENDED_MODE = DECPrivateMode(1006),
         ALTERNATE_SCROLL = DECPrivateMode(1007),
+        XTERM_NumLockMode = DECPrivateMode(1035),
         ASB_AlternateScreenBuffer = DECPrivateMode(1049),
         XTERM_BracketedPasteMode = DECPrivateMode(2004),
         W32IM_Win32InputMode = DECPrivateMode(9001),

src/terminal/adapter/adaptDispatch.cpp

@@ -1938,6 +1938,9 @@ bool AdaptDispatch::_ModeParamsHelper(const DispatchTypes::ModeParams param, con
     case DispatchTypes::ModeParams::ALTERNATE_SCROLL:
         _terminalInput.SetInputMode(TerminalInput::Mode::AlternateScroll, enable);
         return !_PassThroughInputModes();
+    case DispatchTypes::ModeParams::XTERM_NumLockMode:
+        _terminalInput.SetInputMode(TerminalInput::Mode::NumLock, enable);
+        return true;
     case DispatchTypes::ModeParams::ASB_AlternateScreenBuffer:
         _SetAlternateScreenBufferMode(enable);
         return true;
@@ -2076,6 +2079,9 @@ bool AdaptDispatch::RequestMode(const DispatchTypes::ModeParams param)
     case DispatchTypes::ModeParams::ALTERNATE_SCROLL:
         enabled = _terminalInput.GetInputMode(TerminalInput::Mode::AlternateScroll);
         break;
+    case DispatchTypes::ModeParams::XTERM_NumLockMode:
+        enabled = _terminalInput.GetInputMode(TerminalInput::Mode::NumLock);
+        break;
     case DispatchTypes::ModeParams::ASB_AlternateScreenBuffer:
         enabled = _usingAltBuffer;
         break;

src/terminal/input/terminalInput.cpp

@@ -67,7 +67,7 @@ bool TerminalInput::GetInputMode(const Mode mode) const noexcept
 
 void TerminalInput::ResetInputModes() noexcept
 {
-    _inputMode = { Mode::Ansi, Mode::AutoRepeat, Mode::AlternateScroll };
+    _inputMode = { Mode::Ansi, Mode::AutoRepeat, Mode::NumLock, Mode::AlternateScroll };
     _mouseInputState.lastPos = { -1, -1 };
     _mouseInputState.lastButton = 0;
     _initKeyboardMap();
@@ -211,23 +211,34 @@ TerminalInput::OutputType TerminalInput::HandleKey(const INPUT_RECORD& event)
         return _makeNoOutput();
     }
 
+    // NumLock mode is an XTerm extension that changes the behavior of keys on
+    // the numeric keypad, suppressing the effects of KeyPad mode when NumLock
+    // is on. This is for compatibility with Linux apps that have a tendency to
+    // set Keypad mode while not actually wanting the keys to change.
+    const auto numLockMode = _inputMode.test(Mode::NumLock) && WI_IsFlagSet(controlKeyState, NUMLOCK_ON);
+
     // The only enhanced key we care about is the Return key, because that
     // indicates that it's the key on the numeric keypad, which will transmit
-    // different escape sequences when the Keypad mode is enabled.
-    const auto enhancedReturnKey = WI_IsFlagSet(controlKeyState, ENHANCED_KEY) && virtualKeyCode == VK_RETURN;
+    // different escape sequences when the Keypad mode is enabled. But this
+    // doesn't apply when NumLock mode is active.
+    const auto enhancedReturnKey = WI_IsFlagSet(controlKeyState, ENHANCED_KEY) && virtualKeyCode == VK_RETURN && !numLockMode;
 
     // Using the control key state that we calculated above, combined with the
     // virtual key code, we've got a unique identifier for the key combination
-    // that we can lookup in our map of predefined key sequences.
-    auto keyCombo = virtualKeyCode;
-    WI_SetFlagIf(keyCombo, Ctrl, ctrlIsReallyPressed);
-    WI_SetFlagIf(keyCombo, Alt, altIsPressed);
-    WI_SetFlagIf(keyCombo, Shift, shiftIsPressed);
-    WI_SetFlagIf(keyCombo, Enhanced, enhancedReturnKey);
-    const auto keyMatch = _keyMap.find(keyCombo);
-    if (keyMatch != _keyMap.end())
+    // that we can lookup in our map of predefined key sequences. But this is
+    // bypassed for numeric keypad keys when NumLock mode is active.
+    if (!(virtualKeyCode >= VK_NUMPAD0 && virtualKeyCode <= VK_DIVIDE && numLockMode))
     {
-        return keyMatch->second;
+        auto keyCombo = virtualKeyCode;
+        WI_SetFlagIf(keyCombo, Ctrl, ctrlIsReallyPressed);
+        WI_SetFlagIf(keyCombo, Alt, altIsPressed);
+        WI_SetFlagIf(keyCombo, Shift, shiftIsPressed);
+        WI_SetFlagIf(keyCombo, Enhanced, enhancedReturnKey);
+        const auto keyMatch = _keyMap.find(keyCombo);
+        if (keyMatch != _keyMap.end())
+        {
+            return keyMatch->second;
+        }
     }
 
     // If it's not in the key map, we'll use the UnicodeChar, if provided,

src/terminal/input/terminalInput.hpp

@@ -32,6 +32,7 @@ namespace Microsoft::Console::VirtualTerminal
             Keypad,
             CursorKey,
             BackarrowKey,
+            NumLock,
             Win32,
 
             Utf8MouseEncoding,
@@ -77,7 +78,7 @@ namespace Microsoft::Console::VirtualTerminal
         std::wstring _focusInSequence;
         std::wstring _focusOutSequence;
 
-        til::enumset<Mode> _inputMode{ Mode::Ansi, Mode::AutoRepeat, Mode::AlternateScroll };
+        til::enumset<Mode> _inputMode{ Mode::Ansi, Mode::AutoRepeat, Mode::NumLock, Mode::AlternateScroll };
         bool _forceDisableWin32InputMode{ false };
 
         // In the future, if we add support for "8-bit" input mode, these prefixes