From ee79a4e2a10c3f75fc8e24f875e0304fafdcab2b Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Sat, 25 Jan 2020 08:34:03 +1100
Subject: Bug [#2152]. Ignore Alt+Keypad keys that will result in a WM_CHAR.

---
 doc/ScintillaDoc.html     |  6 ++++++
 doc/ScintillaHistory.html |  6 ++++++
 win32/ScintillaWin.cxx    | 33 +++++++++++++++++++++++++++++++--
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/doc/ScintillaDoc.html b/doc/ScintillaDoc.html
index 4ad921cf5..ec1e79afb 100644
--- a/doc/ScintillaDoc.html
+++ b/doc/ScintillaDoc.html
@@ -5549,6 +5549,12 @@ struct Sci_TextToFind {
     If you are building a table, you might
     want to use <code>SCMOD_NORM</code>, which has the value 0, to mean no modifiers.</p>
 
+    <p>On Win32, the numeric keypad with Alt pressed can be used to enter characters by number.
+    This can produce unexpected results in non-numlock mode when function keys are assigned so
+    potentially problematic keys are ignored. For example, setting
+    <code>SCMOD_ALT</code>,<code>SCK_UP</code> will only be active for the Up key on the
+    main cursor keys, not the numeric keypad.</p>
+
     <p><b id="SCI_ASSIGNCMDKEY">SCI_ASSIGNCMDKEY(int <a class="jump"
     href="#keyDefinition">keyDefinition</a>, int sciCommand)</b><br />
      This assigns the given key definition to a Scintilla command identified by
diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 4ed002f36..7ca70eeff 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -571,6 +571,12 @@
 	Fix drag and drop between different encodings by always providing CF_UNICODETEXT only.
 	<a href="https://sourceforge.net/p/scintilla/bugs/2151/">Bug #2151</a>.
 	</li>
+	<li>
+	On Win32, the numeric keypad with Alt pressed can be used to enter characters by number.
+	This can produce unexpected results in non-numlock mode when function keys are assigned.
+	Potentially problematic keys like Alt+KeypadUp are now ignored.
+	<a href="https://sourceforge.net/p/scintilla/bugs/2152/">Bug #2152</a>.
+	</li>
     </ul>
     <h3>
        <a href="https://www.scintilla.org/scite430.zip">Release 4.3.0</a>
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index a2e59687d..4ed03c787 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -169,6 +169,30 @@ bool KeyboardIsKeyDown(int key) noexcept {
 	return (::GetKeyState(key) & 0x80000000) != 0;
 }
 
+constexpr bool KeyboardIsNumericKeypadFunction(uptr_t wParam, sptr_t lParam) {
+	// Bit 24 is the extended keyboard flag and the numeric keypad is non-extended
+	if ((lParam & (1 << 24)) != 0) {
+		// Not from the numeric keypad
+		return false;
+	}
+
+	switch (wParam) {
+	case VK_INSERT:	// 0
+	case VK_END:	// 1
+	case VK_DOWN:	// 2
+	case VK_NEXT:	// 3
+	case VK_LEFT:	// 4
+	case VK_CLEAR:	// 5
+	case VK_RIGHT:	// 6
+	case VK_HOME:	// 7
+	case VK_UP:		// 8
+	case VK_PRIOR:	// 9
+		return true;
+	default:
+		return false;
+	}
+}
+
 }
 
 class ScintillaWin; 	// Forward declaration for COM interface subobjects
@@ -1551,16 +1575,21 @@ sptr_t ScintillaWin::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam
 		case WM_KEYDOWN: {
 				// Platform::DebugPrintf("Keydown %c %c%c%c%c %x %x\n",
 				// iMessage == WM_KEYDOWN ? 'K' : 'S',
-				// (lParam & 1 << 24) ? '-' : 'E',
+				// (lParam & (1 << 24)) ? 'E' : '-',
 				// KeyboardIsKeyDown(VK_SHIFT) ? 'S' : '-',
 				// KeyboardIsKeyDown(VK_CONTROL) ? 'C' : '-',
 				// KeyboardIsKeyDown(VK_MENU) ? 'A' : '-',
 				// wParam, lParam);
 				lastKeyDownConsumed = false;
+				const bool altDown = KeyboardIsKeyDown(VK_MENU);
+				if (altDown && KeyboardIsNumericKeypadFunction(wParam, lParam)) {
+					// Don't interpret these as they may be characters entered by number.
+					return ::DefWindowProc(MainHWND(), iMessage, wParam, lParam);
+				}
 				const int ret = KeyDownWithModifiers(KeyTranslate(static_cast<int>(wParam)),
 					ModifierFlags(KeyboardIsKeyDown(VK_SHIFT),
 					KeyboardIsKeyDown(VK_CONTROL),
-					KeyboardIsKeyDown(VK_MENU)),
+					altDown),
 					&lastKeyDownConsumed);
 				if (!ret && !lastKeyDownConsumed) {
 					return ::DefWindowProc(MainHWND(), iMessage, wParam, lParam);
-- 
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