Fix out-of-bounds when pasting too-long text

Used a `<=` instead of a `<`! How did I mess this up!?

Fixes #2209

projects/common/src/client/java/dan200/computercraft/client/gui/KeyConverter.java

@@ -26,7 +26,8 @@ public class KeyConverter {
         var name = GLFW.glfwGetKeyName(key, scanCode);
         if (name == null || name.length() != 1) return key;
 
-        // If we've got a single character key name, try to translate it to a
+        // If we've got a single character as the key name, treat that as the ASCII value of the key,
+        // and map that back to a key code.
         var character = name.charAt(0);
 
         // 0-9 and A-Z map directly to their GLFW key (they're the same ASCII code).

projects/core/src/main/java/dan200/computercraft/core/util/StringUtil.java

@@ -120,7 +120,7 @@ public final class StringUtil {
         var idx = 0;
 
         var iterator = clipboard.codePoints().iterator();
-        while (iterator.hasNext() && idx <= output.length) {
+        while (iterator.hasNext() && idx < output.length) {
             var chr = unicodeToTerminal(iterator.next());
             if (chr < 0) continue; // Strip out unconvertible characters
             if (!isTypableChar(chr)) break; // Stop at untypable ones.

projects/core/src/test/java/dan200/computercraft/core/util/StringUtilTest.java

@@ -0,0 +1,36 @@
+// SPDX-FileCopyrightText: 2025 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.util;
+
+import dan200.computercraft.api.lua.LuaValues;
+import dan200.computercraft.test.core.ReplaceUnderscoresDisplayNameGenerator;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@DisplayNameGeneration(ReplaceUnderscoresDisplayNameGenerator.class)
+class StringUtilTest {
+    @ParameterizedTest
+    @ValueSource(strings = { "hello\nworld", "hello\n\rworld", "hello\rworld" })
+    public void getClipboardString_returns_a_single_line(String input) {
+        var result = StringUtil.getClipboardString(input);
+        assertEquals(LuaValues.encode("hello"), result);
+    }
+
+    @Test
+    public void getClipboardString_limits_length() {
+        var input = "abcdefghijklmnop".repeat(50);
+        var result = StringUtil.getClipboardString(input);
+        assertEquals(StringUtil.MAX_PASTE_LENGTH, result.limit());
+
+        assertEquals(
+            LuaValues.encode(input.substring(0, StringUtil.MAX_PASTE_LENGTH)),
+            result
+        );
+    }
+}