From bfa16c64f26b83b2dd51bc9bdb135d4896d61197 Mon Sep 17 00:00:00 2001
From: Leonard Hecker <leonard@hecker.io>
Date: Sat, 25 Apr 2020 00:22:05 +0200
Subject: [PATCH] Fix Ctrl+Alt not being treated as a substitute for AltGr
 anymore

This issue was caused by a9c9714.
---
 src/terminal/adapter/ut_adapter/inputTest.cpp |  4 ++--
 src/terminal/input/terminalInput.cpp          | 20 +++++++++----------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/terminal/adapter/ut_adapter/inputTest.cpp b/src/terminal/adapter/ut_adapter/inputTest.cpp
index 1df9bcc714e..406a0292c8a 100644
--- a/src/terminal/adapter/ut_adapter/inputTest.cpp
+++ b/src/terminal/adapter/ut_adapter/inputTest.cpp
@@ -482,7 +482,7 @@ void InputTest::TerminalInputModifierKeyTests()
             // Alt+Key generates [0x1b, Ctrl+key] into the stream
             // Pressing the control key causes all bits but the 5 least
             // significant ones to be zeroed out (when using ASCII).
-            if (AltPressed(uiKeystate) && ControlPressed(uiKeystate) && ch >= 0x40 && ch < 0x7F)
+            if (AltPressed(uiKeystate) && ControlPressed(uiKeystate) && ch > 0x40 && ch <= 0x5A)
             {
                 s_expectedInput.clear();
                 s_expectedInput.push_back(L'\x1b');
@@ -491,7 +491,7 @@ void InputTest::TerminalInputModifierKeyTests()
             }
 
             // Alt+Key generates [0x1b, key] into the stream
-            if (AltPressed(uiKeystate) && ch != 0)
+            if (AltPressed(uiKeystate) && !ControlPressed(uiKeystate) && ch != 0)
             {
                 s_expectedInput.clear();
                 s_expectedInput.push_back(L'\x1b');
diff --git a/src/terminal/input/terminalInput.cpp b/src/terminal/input/terminalInput.cpp
index 948d2f6ad50..d77edca5d60 100644
--- a/src/terminal/input/terminalInput.cpp
+++ b/src/terminal/input/terminalInput.cpp
@@ -498,16 +498,16 @@ bool TerminalInput::HandleKey(const IInputEvent* const pInEvent)
         if (ch == UNICODE_NULL)
         {
             // For Alt+Ctrl+Key messages GetCharData() returns 0.
+            // The values of the ASCII characters and virtual key codes
+            // of <Space>, A-Z (as used below) are numerically identical.
             // -> Get the char from the virtual key.
-            ch = LOWORD(MapVirtualKeyW(keyEvent.GetVirtualKeyCode(), MAPVK_VK_TO_CHAR));
+            ch = keyEvent.GetVirtualKeyCode();
         }
-        if (ch == UNICODE_SPACE)
-        {
-            // Ctrl+@ and Ctrl+Space are supposed to send null bytes.
-            // -> Change Ctrl+Space to Ctrl+@ for compatibility reasons.
-            ch = 0x40;
-        }
-        if (ch >= 0x40 && ch < 0x7F)
+        // Alt+Ctrl acts as a substitute for AltGr on Windows.
+        // For instance using a German keyboard both AltGr+< and Alt+Ctrl+< produce a | (pipe) character.
+        // The below condition primitively ensures that we allow all common Alt+Ctrl combinations
+        // while preserving most of the functionality of Alt+Ctrl as a substitute for AltGr.
+        if (ch == UNICODE_SPACE || (ch > 0x40 && ch <= 0x5A))
         {
             // Pressing the control key causes all bits but the 5 least
             // significant ones to be zeroed out (when using ASCII).
@@ -530,7 +530,7 @@ bool TerminalInput::HandleKey(const IInputEvent* const pInEvent)
 
     // This section is similar to the Alt modifier section above,
     // but handles cases without Ctrl modifiers.
-    if (keyEvent.IsAltPressed() && keyEvent.GetCharData() != 0)
+    if (keyEvent.IsAltPressed() && !keyEvent.IsCtrlPressed() && keyEvent.GetCharData() != 0)
     {
         _SendEscapedInputSequence(keyEvent.GetCharData());
         return true;
@@ -544,7 +544,7 @@ bool TerminalInput::HandleKey(const IInputEvent* const pInEvent)
     // -> Send a "null input sequence" in that case.
     // We don't need to handle other kinds of Ctrl combinations,
     // as we rely on the caller to pretranslate those to characters for us.
-    if (keyEvent.IsCtrlPressed())
+    if (!keyEvent.IsAltPressed() && keyEvent.IsCtrlPressed())
     {
         const auto ch = keyEvent.GetCharData();
         const auto vkey = keyEvent.GetVirtualKeyCode();