Implement backspace for UTF-8 strings

Source/DiabloUI/diabloui.cpp

@@ -27,6 +27,7 @@
 #include "utils/sdl_wrap.h"
 #include "utils/stubs.h"
 #include "utils/language.h"
+#include "utils/utf8.h"
 
 #ifdef __SWITCH__
 // for virtual keyboard on Switch
@@ -330,10 +331,7 @@ void UiFocusNavigation(SDL_Event *event)
 #endif
 			case SDLK_BACKSPACE:
 			case SDLK_LEFT: {
-				int nameLen = strlen(UiTextInput);
-				if (nameLen > 0) {
-					UiTextInput[nameLen - 1] = '\0';
-				}
+				UiTextInput[FindLastUtf8Symbols(UiTextInput)] = '\0';
 				return;
 			}
 			default:

Source/control.cpp

@@ -38,6 +38,7 @@
 #include "utils/language.h"
 #include "utils/sdl_geometry.h"
 #include "utils/stdcompat/optional.hpp"
+#include "utils/utf8.h"
 #include "options.h"
 
 #ifdef _DEBUG
@@ -1802,9 +1803,7 @@ bool control_presskeys(int vkey)
 	} else if (vkey == DVL_VK_RETURN) {
 		ControlPressEnter();
 	} else if (vkey == DVL_VK_BACK) {
-		std::size_t len = strlen(TalkMessage);
-		if (len > 0)
-			TalkMessage[len - 1] = '\0';
+		TalkMessage[FindLastUtf8Symbols(TalkMessage)] = '\0';
 	} else if (vkey == DVL_VK_DOWN) {
 		ControlUpDown(1);
 	} else if (vkey == DVL_VK_UP) {

Source/utils/utf8.h

@@ -65,3 +65,21 @@ inline const char *utf8_decode(const char *buf, uint32_t *c, int *e)
 
 	return reinterpret_cast<const char *>(next);
 }
+
+inline int FindLastUtf8Symbols(const char *text)
+{
+	std::string textBuffer(text);
+	textBuffer.resize(textBuffer.size() + 4); // Buffer must be padded before calling utf8_decode()
+	const char *textData = textBuffer.data();
+	const char *previousPosition = textData;
+
+	uint32_t next;
+	int error;
+	for (; *textData != '\0'; previousPosition = textData) {
+		textData = utf8_decode(textData, &next, &error);
+		if (*textData == '\0')
+			return previousPosition - textBuffer.data();
+	}
+
+	return 0;
+}