Fixed Linux crash caused by wrong mapping of key codes.

CHANGES.md

@@ -11,6 +11,7 @@ Improving stability
 - Improved hot-reload stability and support for reloading after recompiling outside of the editor. Both methods should be equally supported and work together.
 - Improved behaviour of delegates when hot-reloading.
 - Changed context index mapping to fix issues with multi-PIE debugging in 4.25.
+- Fixed Linux crash caused by wrong mapping of key codes.
 
 Version: 1.20 (2020/06)
 Transition to IWYU and maintenance:

Source/ImGui/Private/ImGuiInteroperability.cpp

@@ -122,6 +122,17 @@ namespace ImGuiInterops
 		Copy(Mapping.KeyMap, IO.KeyMap);
 	}
 
+	// Simple transform mapping key codes to 0-511 range used in ImGui.
+	// From what I can tell, on most supported platforms key codes should comfortably fit in that range anyway
+	// but the SDL key-codes used on Linux can go way out of this range (because of the extra flag). However,
+	// after this transform they should fit in the range without conflicts.
+	// NOTE: Should any of the platforms have other conflicts or any trouble with inputs, this is the likely
+	// candidate for change.
+	static uint32 MapKeyCode(uint32 KeyCode)
+	{
+		return (KeyCode < 512) ? KeyCode : 256 + (KeyCode % 256);
+	}
+
 	uint32 GetKeyIndex(const FKey& Key)
 	{
 		const uint32* pKeyCode = nullptr;
@@ -129,17 +140,17 @@ namespace ImGuiInterops
 
 		FInputKeyManager::Get().GetCodesFromKey(Key, pKeyCode, pCharCode);
 
-		if (pKeyCode)
-		{
-			return *pKeyCode;
+		const uint32 KeyCode =
+			pKeyCode ? *pKeyCode
+			: pCharCode ? *pCharCode
+			: 0;
+
+		return MapKeyCode(KeyCode);
 	}
 
-		if (pCharCode)
+	uint32 GetKeyIndex(const FKeyEvent& KeyEvent)
 	{
-			return *pCharCode;
-		}
-
-		return 0;
+		return MapKeyCode(KeyEvent.GetKeyCode());
 	}
 
 	uint32 GetMouseIndex(const FKey& MouseButton)

Source/ImGui/Private/ImGuiInteroperability.h

@@ -40,10 +40,7 @@ namespace ImGuiInterops
 	uint32 GetKeyIndex(const FKey& Key);
 
 	// Map key event to index in keys buffer.
-	FORCEINLINE uint32 GetKeyIndex(const FKeyEvent& KeyEvent)
-	{
-		return KeyEvent.GetKeyCode();
-	}
+	uint32 GetKeyIndex(const FKeyEvent& KeyEvent);
 
 	// Map mouse FKey to index in mouse buttons buffer.
 	uint32 GetMouseIndex(const FKey& MouseButton);