Fix SendInput handling (#7900)

While not explicitly permitted, a wide range of software (including
Windows' own touch keyboard) sets the `wScan` member of the `KEYBDINPUT`
structure to 0, resulting in `scanCode` being 0 as well.  In these
situations we'll now use the `vkey` to get a `scanCode`.

Validation
----------
* AutoHotkey
  * Use a keyboard layout with `AltGr` key
  * Execute the following script:
    ```ahk
    #NoEnv
    #Warn
    SendMode Input
    SetWorkingDir %A_ScriptDir%
    <^>!8::SendInput {Raw}»
    ```
  * Press `AltGr+8` while the Terminal is in the foreground
  * Ensure » is being echoed ✔️
* PowerToys
  * Add a `Ctrl+I -> ↑ (up arrow)` keyboard shortcut
  * Press `Ctrl+I` while the Terminal is in the foreground
  * Ensure the shell history is being navigated backwards ✔️
* Windows Touch Keyboard
  * Right-click or tap and hold the taskbar and select "Show touch
    keyboard" button
  * Open touch keyboard
  * Ensure keyboard works like a regular keyboard ✔️
  * Ensure unicode characters are echoed on the Terminal as well (except
    for Emojis) ✔️

Closes #7438
Closes #7495
Closes #7843

.github/actions/spell-check/expect/655f007265b351e140d20b3976792523ad689241.txt

@@ -0,0 +1,7 @@
+autogenerated
+CPPCORECHECK
+Debian
+filepath
+inplace
+KEYBDINPUT
+WINVER

.github/actions/spell-check/expect/expect.txt

@@ -33,7 +33,6 @@ AHelper
 ahz
 AImpl
 AInplace
-akb
 ALIGNRIGHT
 alloc
 allocing
@@ -62,7 +61,6 @@ apiset
 apos
 APPBARDATA
 appconsult
-appdata
 APPICON
 appium
 applet
@@ -109,10 +107,8 @@ aumid
 Authenticode
 AUTOBUDDY
 AUTOCHECKBOX
-Autogenerated
 autohide
 AUTOHSCROLL
-autologin
 automagically
 autopositioning
 AUTORADIOBUTTON
@@ -393,7 +389,6 @@ CPINFOEX
 cplinfo
 cplusplus
 cpp
-cppcorecheck
 cppcorecheckrules
 cpprest
 cpprestsdk
@@ -510,10 +505,8 @@ DDESHARE
 DDevice
 DEADCHAR
 dealloc
-debian
 debolden
 debounce
-debugbreak
 DECALN
 DECANM
 DECAUPSS
@@ -521,11 +514,9 @@ DECAWM
 DECCKM
 DECCOLM
 DECEKBD
-decf
 DECKPAM
 DECKPM
 DECKPNM
-DECLL
 DECLRMM
 decls
 declspec
@@ -552,7 +543,6 @@ DECSEL
 DECSET
 DECSLPP
 DECSLRM
-DECSMBV
 DECSMKR
 DECSR
 decstandar
@@ -716,7 +706,6 @@ EPres
 ERASEBKGND
 errno
 errorlevel
-esa
 ETB
 etcoreapp
 ETW
@@ -771,7 +760,6 @@ fgetwc
 fgidx
 FILEDESCRIPTION
 fileno
-FILEPATH
 FILESUBTYPE
 FILESYSPATH
 filesystem
@@ -932,7 +920,6 @@ GTP
 guc
 gui
 guidatom
-guidgenerator
 GValue
 GWL
 GWLP
@@ -1105,7 +1092,6 @@ Inlines
 INotify
 inout
 INPATHROOT
-Inplace
 inproc
 Inputkeyinfo
 INPUTPROCESSORPROFILE
@@ -1194,11 +1180,9 @@ kcud
 kcuf
 kcuu
 Kd
-keith
 kernelbase
 kernelbasestaging
 keybinding
-keybound
 keychord
 keydown
 keyevent
@@ -1471,7 +1455,6 @@ namestream
 Namquiseratal
 nano
 natvis
-naws
 nbsp
 Nc
 NCCALCSIZE
@@ -1553,7 +1536,6 @@ NOTNULL
 NOTOPMOST
 NOTRACK
 NOTSUPPORTED
-notypeopt
 nouicompat
 nounihan
 NOUPDATE
@@ -1628,7 +1610,6 @@ opencon
 openconsole
 OPENIF
 OPENLINK
-openlogo
 openps
 opensource
 openvt
@@ -1968,7 +1949,6 @@ resheader
 resizable
 resmimetype
 restrictedcapabilities
-restrictederrorinfo
 resw
 resx
 retval
@@ -1995,7 +1975,6 @@ rgw
 rgwch
 rhs
 ri
-richturn
 RIGHTALIGN
 RIGHTBUTTON
 riid
@@ -2069,7 +2048,6 @@ SCROLLSCALE
 SCROLLSCREENBUFFER
 Scrollup
 Scrolluppage
-Scs
 scursor
 sddl
 sdeleted
@@ -2243,7 +2221,6 @@ subkey
 SUBLANG
 sublicensable
 submenu
-subnegotiation
 subresource
 subspan
 substr
@@ -2254,7 +2231,6 @@ svg
 swapchain
 swapchainpanel
 swappable
-Switchto
 SWMR
 SWP
 swprintf
@@ -2309,7 +2285,6 @@ technet
 tellp
 telnet
 telnetd
-telnetpp
 templated
 terminalcore
 TERMINALSCROLLING
@@ -2706,12 +2681,10 @@ wintelnet
 winternl
 winuser
 winuserp
-winver
 wistd
 wixproj
 wline
 wlinestream
-Wlk
 wmain
 WMSZ
 wnd
@@ -2754,7 +2727,6 @@ WRunoff
 WScript
 wsl
 WSLENV
-wslhome
 wsmatch
 WSpace
 wss

src/cascadia/TerminalCore/Terminal.cpp

@@ -472,15 +472,20 @@ bool Terminal::SendKeyEvent(const WORD vkey,
 
     _StoreKeyEvent(vkey, scanCode);
 
-    // As a Terminal we're mostly interested in getting key events from physical hardware (mouse & keyboard).
+    // Certain applications like AutoHotKey and its keyboard remapping feature,
-    // We're thus ignoring events whose values are outside the valid range and unlikely to be generated by the current keyboard.
+    // send us key events using SendInput() whose values are outside of the valid range.
-    // It's very likely that a proper followup character event will be sent to us.
-    // This prominently happens using AutoHotKey's keyboard remapping feature,
-    // which sends input events whose vkey is 0xff and scanCode is 0.
-    // We need to check for this early, as _CharacterFromKeyEvent() always returns 0 for such invalid values,
-    // making us believe that this is an actual non-character input, while it usually isn't.
     // GH#7064
-    if (vkey == 0 || vkey >= 0xff || scanCode == 0)
+    if (vkey == 0 || vkey >= 0xff)
+    {
+        return false;
+    }
+
+    // While not explicitly permitted, a wide range of software, including Windows' own touch keyboard,
+    // sets the wScan member of the KEYBDINPUT structure to 0, resulting in scanCode being 0 as well.
+    // --> Alternatively get the scanCode from the vkey if possible.
+    // GH#7495
+    const auto sc = scanCode ? scanCode : _ScanCodeFromVirtualKey(vkey);
+    if (sc == 0)
     {
         return false;
     }
@@ -506,7 +511,7 @@ bool Terminal::SendKeyEvent(const WORD vkey,
     // is the underlying ASCII character (e.g. A-Z) on the keyboard in our case.
     // See GH#5525/GH#6211 for more details
     const auto isSuppressedAltGrAlias = !_altGrAliasing && states.IsAltPressed() && states.IsCtrlPressed() && !states.IsAltGrPressed();
-    const auto ch = isSuppressedAltGrAlias ? UNICODE_NULL : _CharacterFromKeyEvent(vkey, scanCode, states);
+    const auto ch = isSuppressedAltGrAlias ? UNICODE_NULL : _CharacterFromKeyEvent(vkey, sc, states);
 
     // Delegate it to the character event handler if this key event can be
     // mapped to one (see method description above). For Alt+key combinations
@@ -521,7 +526,7 @@ bool Terminal::SendKeyEvent(const WORD vkey,
         return false;
     }
 
-    KeyEvent keyEv{ keyDown, 1, vkey, scanCode, ch, states.Value() };
+    KeyEvent keyEv{ keyDown, 1, vkey, sc, ch, states.Value() };
     return _terminalInput->HandleKey(&keyEv);
 }
 
@@ -638,8 +643,6 @@ WORD Terminal::_VirtualKeyFromCharacter(const wchar_t ch) noexcept
 wchar_t Terminal::_CharacterFromKeyEvent(const WORD vkey, const WORD scanCode, const ControlKeyStates states) noexcept
 try
 {
-    const auto sc = scanCode != 0 ? scanCode : _ScanCodeFromVirtualKey(vkey);
-
     // We might want to use GetKeyboardState() instead of building our own keyState.
     // The question is whether that's necessary though. For now it seems to work fine as it is.
     std::array<BYTE, 256> keyState = {};
@@ -658,7 +661,7 @@ try
     // * If bit 0 is set, a menu is active.
     //   If this flag is not specified ToUnicodeEx will send us character events on certain Alt+Key combinations (e.g. Alt+Arrow-Up).
     // * If bit 2 is set, keyboard state is not changed (Windows 10, version 1607 and newer)
-    const auto result = ToUnicodeEx(vkey, sc, keyState.data(), buffer.data(), gsl::narrow_cast<int>(buffer.size()), 0b101, nullptr);
+    const auto result = ToUnicodeEx(vkey, scanCode, keyState.data(), buffer.data(), gsl::narrow_cast<int>(buffer.size()), 0b101, nullptr);
 
     // TODO:GH#2853 We're only handling single UTF-16 code points right now, since that's the only thing KeyEvent supports.
     return result == 1 || result == -1 ? buffer.at(0) : 0;

src/cascadia/UnitTests_TerminalCore/InputTest.cpp

@@ -71,9 +71,7 @@ namespace TerminalCoreUnitTests
     {
         // Certain applications like AutoHotKey and its keyboard remapping feature,
         // send us key events using SendInput() whose values are outside of the valid range.
-        // We don't want to handle those events as we're probably going to get a proper followup character event.
         VERIFY_IS_FALSE(term.SendKeyEvent(0, 123, {}, true));
         VERIFY_IS_FALSE(term.SendKeyEvent(255, 123, {}, true));
-        VERIFY_IS_FALSE(term.SendKeyEvent(123, 0, {}, true));
     }
 }