Remove dependency on the java.desktop module

The Favicon.create(BufferedImage) method has been removed. In its place we have Favicon.create(Path) (carried over from the 1.x.x series) and Favicon.create(byte[]) (brand new).

api/src/main/java/com/velocitypowered/api/util/Favicon.java

@@ -1,15 +1,11 @@
 package com.velocitypowered.api.util;
 
 import com.google.common.base.Preconditions;
-import java.awt.image.BufferedImage;
-import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Base64;
 import java.util.Objects;
-import javax.imageio.ImageIO;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
@@ -65,23 +61,17 @@ public final class Favicon {
   }
 
   /**
-   * Creates a new {@code Favicon} from the specified {@code image}.
+   * Creates a new {@code Favicon} from the specified {@code buffer}.
    *
-   * @param image the image to use for the favicon
+   * @param buffer the buffer to use for the favicon
    * @return the created {@link Favicon} instance
+   * @throws IOException if the file could not be read from the path
    */
-  public static Favicon create(BufferedImage image) {
-    Preconditions.checkNotNull(image, "image");
-    Preconditions.checkArgument(image.getWidth() == 64 && image.getHeight() == 64,
-        "Image is not 64x64 (found %sx%s)", image.getWidth(),image.getHeight());
-    ByteArrayOutputStream os = new ByteArrayOutputStream();
-    try {
-      ImageIO.write(image, "PNG", os);
-    } catch (IOException e) {
-      throw new AssertionError(e);
+  public static Favicon create(byte[] buffer) throws IOException {
+    if (!FaviconChecker.check(buffer)) {
+      throw new IllegalArgumentException("Image is not a PNG file or does not have 64x64 dimensions");
     }
-    return new Favicon(
-        "data:image/png;base64," + Base64.getEncoder().encodeToString(os.toByteArray()));
+    return new Favicon("data:image/png;base64," + Base64.getEncoder().encodeToString(buffer));
   }
 
   /**
@@ -92,12 +82,6 @@ public final class Favicon {
    * @throws IOException if the file could not be read from the path
    */
   public static Favicon create(Path path) throws IOException {
-    try (InputStream stream = Files.newInputStream(path)) {
-      BufferedImage image = ImageIO.read(stream);
-      if (image == null) {
-        throw new IOException("Unable to read the image.");
-      }
-      return create(image);
-    }
+    return create(Files.readAllBytes(path));
   }
 }

api/src/main/java/com/velocitypowered/api/util/FaviconChecker.java

@@ -0,0 +1,34 @@
+package com.velocitypowered.api.util;
+
+import java.nio.ByteBuffer;
+
+class FaviconChecker {
+  private static final byte[] PNG_MAGIC = new byte[] {
+      (byte) 137, 80, 78, 71, 13, 10, 26, 10
+  };
+  private static final byte[] IHDR_NAME = new byte[] {
+      73, 72, 68, 82
+  };
+
+  public static boolean check(byte[] data) {
+    ByteBuffer buf = ByteBuffer.wrap(data);
+
+    for (byte value : PNG_MAGIC) {
+      if (buf.get() != value) {
+        return false;
+      }
+    }
+
+    buf.position(buf.position() + 4);
+    for (byte value : IHDR_NAME) {
+      if (buf.get() != value) {
+        return false;
+      }
+    }
+
+    int width = buf.getInt();
+    int height = buf.getInt();
+
+    return width == 64 && height == 64;
+  }
+}

api/src/test/java/com/velocitypowered/api/util/FaviconCheckerTest.java

@@ -0,0 +1,33 @@
+package com.velocitypowered.api.util;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.google.common.io.Resources;
+import java.io.IOException;
+import org.junit.jupiter.api.Test;
+
+public class FaviconCheckerTest {
+
+  @Test
+  void handlesProperlyFormattedFavicon() throws IOException {
+    assertTrue(FaviconChecker.check(readFile("test_icon_dimensions_correct.png")),
+        "Correctly formatted favicon is not valid");
+  }
+
+  @Test
+  void handlesBadDimensionFavicon() throws IOException {
+    assertFalse(FaviconChecker.check(readFile("test_icon_dimensions_wrong.png")),
+        "Incorrect dimension favicon is valid?");
+  }
+
+  @Test
+  void handlesBadFormatFavicon() throws IOException {
+    assertFalse(FaviconChecker.check(readFile("test_icon_dimensions_wrong_format.jpg")),
+        "Incorrect format favicon is valid?");
+  }
+
+  private static byte[] readFile(String path) throws IOException {
+    return Resources.toByteArray(FaviconCheckerTest.class.getResource(path));
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/Velocity.java

@@ -11,10 +11,6 @@ public class Velocity {
   private static final Logger logger = LogManager.getLogger(Velocity.class);
 
   static {
-    // We use BufferedImage for favicons, and on macOS this puts the Java application in the dock.
-    // How inconvenient. Force AWT to work with its head chopped off.
-    System.setProperty("java.awt.headless", "true");
-
     // By default, Netty allocates 16MiB arenas for the PooledByteBufAllocator. This is too much
     // memory for Minecraft, which imposes a maximum packet size of 2MiB! We'll use 4MiB as a more
     // sane default.