diff -r e254398fcc7c -r 20ca0a6be175 sources/interface.cpp
--- a/sources/interface.cpp	Wed Jan 27 13:17:11 2021 +0200
+++ b/sources/interface.cpp	Wed Jan 27 14:04:53 2021 +0200
@@ -203,13 +203,13 @@
 //
 void Interface::renderTitlebar()
 {
-	if (m_title.length() <= COLS)
+	if (static_cast<signed>(m_title.length()) <= COLS)
 	{
 		chtype pair = getColorPair(WHITE, BLUE);
 		int startx =(COLS - m_title.length()) / 2;
 		int endx = startx + m_title.length();
 		attron(pair);
-		mvprintw(0, startx, "%s", m_title.chars());
+		mvprintw(0, startx, "%s", m_title.data());
 		mvhline(0, 0, ' ', startx);
 		mvhline(0, endx, ' ', COLS - endx);
 		attroff(pair);
@@ -430,7 +430,7 @@
 	}
 
 	// Ensure the cursor is within bounds
-	m_cursorPosition = clamp(m_cursorPosition, 0, displayString.length());
+	m_cursorPosition = clamp(m_cursorPosition, 0, static_cast<signed>(displayString.length()));
 
 	// Ensure that the cursor is always in view, adjust panning if this is not the case
 	if (m_cursorPosition > m_inputPanning + displayLength)
@@ -445,11 +445,11 @@
 
 	// Render the input string
 	mvhline(LINES - 2, 0, ' ', COLS);
-	mvprintw(y, prompt.length() + 1, "%s", displayString.mid(start, end).chars());
+	mvprintw(y, prompt.length() + 1, "%s", mid(displayString, start, end).data());
 
 	// Render the prompt
 	attron(promptColor);
-	mvprintw(y, 0, "%s", prompt.chars());
+	mvprintw(y, 0, "%s", prompt.data());
 	attroff(promptColor);
 
 	// Store in memory where the cursor is now(so that we can re-draw it to position the terminal
@@ -468,7 +468,7 @@
 	int y = LINES - 1;
 	attron(color);
 	mvhline(y, 0, ' ', COLS);
-	mvprintw(y, 0, "%s", m_statusBarText.chars());
+	mvprintw(y, 0, "%s", m_statusBarText.data());
 	attroff(color);
 	m_needRefresh = true;
 	m_needStatusBarRender = false;
@@ -501,19 +501,19 @@
 			}
 			else
 			{
-				adminText.sprintf("%d other admin%s", m_session.getAdminCount(),
+				adminText = zfc::sprintf("%d other admin%s", m_session.getAdminCount(),
 					m_session.getAdminCount() != 1 ? "s" : "");
 			}
 
-			text.sprintf("%s | %s | %s",
-				m_session.address().to_string(IPAddress::WITH_PORT).chars(),
-				m_session.getLevel().chars(),
-				adminText.chars());
+			text = zfc::sprintf("%s | %s | %s",
+				m_session.address().to_string(IPAddress::WITH_PORT).data(),
+				m_session.getLevel().data(),
+				adminText.data());
 		}
 		break;
 	}
 
-	if (not text.isEmpty())
+	if (not text.empty())
 		text += " | ";
 
 	text += "Ctrl+N to connect, Ctrl+Q to ";
@@ -580,7 +580,7 @@
 	int pos = m_cursorPosition;
 
 	// Move past current whitespace
-	while (pos < input.length() and isspace(input[pos]))
+	while (pos < static_cast<signed>(input.length()) and isspace(input[pos]))
 		pos++;
 
 	// Move past the word
@@ -601,8 +601,8 @@
 		m_cursorPosition = a;
 
 	String& input = getEditableInput();
-	m_pasteBuffer = input.mid(a, b);
-	input.remove(a, b - a);
+	m_pasteBuffer = mid(input, a, b);
+	input = remove_range(input, a, b - a);
 	m_needInputRender = true;
 }
 
@@ -637,7 +637,9 @@
 
 	if (ch >= 0x20 and ch <= 0x7E)
 	{
-		getEditableInput().insert(m_cursorPosition++, char(ch));
+		std::string& input = getEditableInput();
+		input.insert(input.begin() + m_cursorPosition, char(ch));
+		m_cursorPosition += 1;
 		m_needInputRender = true;
 	}
 	else switch (ch)
@@ -683,7 +685,7 @@
 
 	case KEY_RIGHT:
 	case 'F' - 'A' + 1: // readline ^F
-		if (m_cursorPosition < getCurrentInput().length())
+		if (m_cursorPosition < static_cast<int>(getCurrentInput().length()))
 		{
 			m_cursorPosition++;
 			m_needInputRender = true;
@@ -706,7 +708,7 @@
 
 	case KEY_END:
 	case 'E' - 'A' + 1: // readline ^E
-		if (m_cursorPosition != getCurrentInput().length())
+		if (m_cursorPosition != static_cast<signed>(getCurrentInput().length()))
 		{
 			m_cursorPosition = getCurrentInput().length();
 			m_needInputRender = true;
@@ -717,16 +719,19 @@
 	case '\b':
 		if (m_cursorPosition > 0)
 		{
-			getEditableInput().removeAt(--m_cursorPosition);
+			String& input = getEditableInput();
+			input.erase(input.begin() + m_cursorPosition);
+			m_cursorPosition -= 1;
 			m_needInputRender = true;
 		}
 		break;
 
 	case KEY_DC:
 	case 'D' - 'A' + 1: // readline ^D
-		if (m_cursorPosition < getCurrentInput().length())
+		if (m_cursorPosition < static_cast<signed>(getCurrentInput().length()))
 		{
-			getEditableInput().removeAt(m_cursorPosition);
+			String& input = getEditableInput();
+			input.erase(input.begin() + m_cursorPosition);
 			m_needInputRender = true;
 		}
 		break;
@@ -758,7 +763,7 @@
 		break;
 
 	case 'Y' - 'A' + 1: // readline ^Y - paste previously deleted text
-		if (not m_pasteBuffer.isEmpty())
+		if (not m_pasteBuffer.empty())
 		{
 			getEditableInput().insert(m_cursorPosition, m_pasteBuffer);
 			m_cursorPosition += m_pasteBuffer.length();
@@ -774,7 +779,7 @@
 				and m_cursorPosition > 0
 				and(space == -1 or space >= m_cursorPosition))
 			{
-				String start = getCurrentInput().mid(0, m_cursorPosition);
+				String start = mid(getCurrentInput(), 0, m_cursorPosition);
 				m_session.requestTabCompletion(start);
 			}
 		}
@@ -806,7 +811,7 @@
 			break;
 
 		case INPUTSTATE_PASSWORD:
-			if (m_inputState == INPUTSTATE_PASSWORD and not getCurrentInput().isEmpty())
+			if (m_inputState == INPUTSTATE_PASSWORD and not getCurrentInput().empty())
 			{
 				m_session.disconnect();
 				m_session.setPassword(getCurrentInput());
@@ -904,7 +909,7 @@
 void Interface::vprint(const char* fmtstr, va_list args)
 {
 	String message;
-	message.vsprintf(fmtstr, args);
+	message = vsprintf(fmtstr, args);
 	printToConsole(message);
 }
 
@@ -957,7 +962,7 @@
 {
 	// Zandronum sometimes sends color codes as "\\c" and sometimes as "\x1C".
 	// Let's correct that on our end and hope this won't cause conflicts.
-	message.replace("\\c", "\x1C");
+	replace_all(message, "\\c", "\x1C");
 
 	for (char ch : message)
 	{
@@ -1034,7 +1039,7 @@
 {
 	String& input = getEditableInput();
 
-	if (input.startsWith(part))
+	if (starts_with(input, part))
 	{
 		if (input[part.length()] != ' ')
 			complete += ' ';
@@ -1052,8 +1057,8 @@
 	if (input[0] != '/')
 		return;
 
-	StringList args = input.right(input.length() - 1).split(" ");
-	String command = args[0].toLowerCase();
+	StringList args = split(right(input, input.length() - 1), " ");
+	String command = to_lowercase(args[0]);
 	args.erase(args.begin());
 
 	if (command == "connect")
@@ -1095,14 +1100,14 @@
 		throw Exitception();
 	}
 	else
-		printError("Unknown command: %s\n", command.chars());
+		printError("Unknown command: %s\n", command.data());
 }
 
 // -------------------------------------------------------------------------------------------------
 //
 void Interface::disconnected()
 {
-	print("Disconnected from %s\n", m_session.address().to_string(IPAddress::WITH_PORT).chars());
+	print("Disconnected from %s\n", m_session.address().to_string(IPAddress::WITH_PORT).data());
 	resetTitle();
 	renderFull();
 }
@@ -1111,7 +1116,7 @@
 //
 void Interface::resetTitle()
 {
-	m_title.sprintf("%s %s (%s)", application_name(), full_version_string(), changeset_date_string());
+	m_title = sprintf("%s %s (%s)", application_name(), full_version_string(), changeset_date_string());
 }
 
 // -------------------------------------------------------------------------------------------------