Fix SGR mouse movement reports (#18864)

According to the documentation, the final character of an SGR mouse
report is meant to be `M` for a button press and `m` for a button
release. However it isn't clear what the final character should be for
motion events, and we were using an `m` if there weren't any buttons
held down at the time, while all other terminals used an `M`, regardless
of the button state.

This PR updates our implementation to match what everyone else is doing,
since our interpretation of the spec was causing problems for some apps.

## Validation Steps Performed

I've manually tested the new behavior in Vttest, and confirmed that our
mouse reports now match Xterm more closely, and I've tested with v0.42.0
of Zellij, which was previous glitching badly in Windows Terminal, but
now works correctly.

I've also updated our unit tests for the SGR mouse mode to reflect the
correct report format.

Closes #18712

src/terminal/adapter/ut_adapter/MouseInputTest.cpp

@@ -99,7 +99,7 @@ public:
 
         TerminalInput::StringType str;
         str.append(std::wstring_view{ buffer });
-        str[str.size() - 1] = IsButtonDown(uiButton) ? L'M' : L'm';
+        str[str.size() - 1] = IsButtonUp(uiButton) ? L'm' : L'M';
         return str;
     }
 
@@ -182,23 +182,18 @@ public:
         return result;
     }
 
-    bool IsButtonDown(unsigned int uiButton)
+    bool IsButtonUp(unsigned int uiButton)
     {
-        auto fIsDown = false;
         switch (uiButton)
         {
-        case WM_LBUTTONDBLCLK:
-        case WM_LBUTTONDOWN:
-        case WM_RBUTTONDOWN:
-        case WM_RBUTTONDBLCLK:
-        case WM_MBUTTONDOWN:
-        case WM_MBUTTONDBLCLK:
-        case WM_MOUSEWHEEL:
-        case WM_MOUSEHWHEEL:
-            fIsDown = true;
-            break;
+        case WM_LBUTTONUP:
+        case WM_RBUTTONUP:
+        case WM_MBUTTONUP:
+        case WM_XBUTTONUP:
+            return true;
+        default:
+            return false;
         }
-        return fIsDown;
     }
 
     /* From winuser.h - Needed to manually specify the test properties

src/terminal/input/mouseInput.cpp

@@ -63,24 +63,19 @@ static constexpr bool _isWheelMsg(const unsigned int buttonCode) noexcept
 }
 
 // Routine Description:
-// - Determines if the input windows message code describes a button press
-//     (either down or doubleclick)
+// - Determines if the input windows message code describes a button release
 // Parameters:
 // - button - the message to decode.
 // Return value:
-// - true if button is a button down event
-static constexpr bool _isButtonDown(const unsigned int button) noexcept
+// - true if button is a button up event
+static constexpr bool _isButtonUp(const unsigned int button) noexcept
 {
     switch (button)
     {
-    case WM_LBUTTONDBLCLK:
-    case WM_LBUTTONDOWN:
-    case WM_RBUTTONDOWN:
-    case WM_RBUTTONDBLCLK:
-    case WM_MBUTTONDOWN:
-    case WM_MBUTTONDBLCLK:
-    case WM_MOUSEWHEEL:
-    case WM_MOUSEHWHEEL:
+    case WM_LBUTTONUP:
+    case WM_RBUTTONUP:
+    case WM_MBUTTONUP:
+    case WM_XBUTTONUP:
         return true;
     default:
         return false;
@@ -372,7 +367,7 @@ TerminalInput::OutputType TerminalInput::HandleMouse(const til::point position,
                 // then we want to handle hovers with WM_MOUSEMOVE.
                 // However, if we're dragging (WM_MOUSEMOVE with a button pressed),
                 //      then use that pressed button instead.
-                return _GenerateSGRSequence(position, physicalButtonPressed ? realButton : button, _isButtonDown(realButton), isHover, modifierKeyState, delta);
+                return _GenerateSGRSequence(position, physicalButtonPressed ? realButton : button, _isButtonUp(button), isHover, modifierKeyState, delta);
             }
             else
             {
@@ -463,18 +458,18 @@ TerminalInput::OutputType TerminalInput::_GenerateUtf8Sequence(const til::point
 // Parameters:
 // - position - The windows coordinates (top,left = 0,0) of the mouse event
 // - button - the message to decode. WM_MOUSEMOVE is used for mouse hovers with no buttons pressed.
-// - isDown - true if a mouse button was pressed.
+// - isRelease - true if a mouse button was released.
 // - isHover - true if the sequence is generated in response to a mouse hover
 // - modifierKeyState - the modifier keys pressed with this button
 // - delta - the amount that the scroll wheel changed (should be 0 unless button is a WM_MOUSE*WHEEL)
 // - ppwchSequence - On success, where to put the pointer to the generated sequence
 // - pcchLength - On success, where to put the length of the generated sequence
-TerminalInput::OutputType TerminalInput::_GenerateSGRSequence(const til::point position, const unsigned int button, const bool isDown, const bool isHover, const short modifierKeyState, const short delta)
+TerminalInput::OutputType TerminalInput::_GenerateSGRSequence(const til::point position, const unsigned int button, const bool isRelease, const bool isHover, const short modifierKeyState, const short delta)
 {
     // Format for SGR events is:
-    // "\x1b[<%d;%d;%d;%c", xButton, x+1, y+1, fButtonDown? 'M' : 'm'
+    // "\x1b[<%d;%d;%d;%c", xButton, x+1, y+1, isRelease? 'm' : 'M'
     const auto xbutton = _windowsButtonToSGREncoding(button, isHover, modifierKeyState, delta);
-    return fmt::format(FMT_COMPILE(L"{}<{};{};{}{}"), _csi, xbutton, position.x + 1, position.y + 1, isDown ? L'M' : L'm');
+    return fmt::format(FMT_COMPILE(L"{}<{};{};{}{}"), _csi, xbutton, position.x + 1, position.y + 1, isRelease ? L'm' : L'M');
 }
 
 // Routine Description:

src/terminal/input/terminalInput.hpp

@@ -109,7 +109,7 @@ namespace Microsoft::Console::VirtualTerminal
 #pragma region MouseInput
         [[nodiscard]] OutputType _GenerateDefaultSequence(til::point position, unsigned int button, bool isHover, short modifierKeyState, short delta);
         [[nodiscard]] OutputType _GenerateUtf8Sequence(til::point position, unsigned int button, bool isHover, short modifierKeyState, short delta);
-        [[nodiscard]] OutputType _GenerateSGRSequence(til::point position, unsigned int button, bool isDown, bool isHover, short modifierKeyState, short delta);
+        [[nodiscard]] OutputType _GenerateSGRSequence(til::point position, unsigned int button, bool isRelease, bool isHover, short modifierKeyState, short delta);
 
         [[nodiscard]] OutputType _makeAlternateScrollOutput(short delta) const;