libprocessing ffi error handling (#1293)

* FFI error setup

* Clear before init.

Author: tychedelia

core/src/processing/webgpu/PGraphicsWebGPU.java

@@ -0,0 +1,4 @@
+package processing.webgpu;
+
+public class PGraphicsWebGPU {
+}

core/src/processing/webgpu/PWebGPU.java

@@ -1,15 +1,21 @@
 package processing.webgpu;
 
 import processing.core.NativeLibrary;
-import processing.ffi.processing_h;
+
+import java.lang.foreign.MemorySegment;
+
+import static java.lang.foreign.MemorySegment.NULL;
+import static processing.ffi.processing_h.processing_check_error;
+import static processing.ffi.processing_h.processing_init;
 
 /**
  * PWebGPU provides the native interface layer for libProcessing's WebGPU support.
  */
 public class PWebGPU {
 
     static {
-        NativeLibrary.ensureLoaded();
+        ensureLoaded();
+        init();
     }
 
     /**
@@ -20,9 +26,25 @@ public static void ensureLoaded() {
     }
 
     /**
-     * It's just math, silly!
+     * Initializes the WebGPU subsystem. Must be called before any other WebGPU methods.
+     */
+    public static void init() {
+        processing_init();
+        checkError();
+    }
+
+    /**
+     * Checks for errors from the native library and throws a PWebGPUException if an error occurred.
      */
-    public static long add(long left, long right) {
-        return processing_h.processing_add(left, right);
+    private static void checkError() {
+        MemorySegment ret = processing_check_error();
+        if (ret.equals(NULL)) {
+            return;
+        }
+
+        String errorMsg = ret.getString(0);
+        if (errorMsg != null && !errorMsg.isEmpty()) {
+            throw new PWebGPUException(errorMsg);
+        }
     }
 }

core/src/processing/webgpu/PWebGPUException.java

@@ -0,0 +1,13 @@
+package processing.webgpu;
+
+/**
+ * Unchecked exception thrown for WebGPU-related errors.
+ * <p>
+ * WebGPU operations can fail for various reasons, such as unsupported hardware, but are not
+ * expected to be recoverable by the Processing application.
+ */
+public class PWebGPUException extends RuntimeException {
+    public PWebGPUException(String message) {
+        super(message);
+    }
+}

core/test/processing/webgpu/PWebGPUTest.java

@@ -1,15 +1,13 @@
 package processing.webgpu;
 
 import org.junit.Test;
-import static org.junit.Assert.*;
 
 /**
  * Tests for the PWebGPU native interface.
  */
 public class PWebGPUTest {
     @Test
-    public void testAddFunction() {
-        long result = PWebGPU.add(2, 2);
-        assertEquals("2 + 2 should equal 4", 4L, result);
+    public void itLoads() {
+        PWebGPU.ensureLoaded();
     }
 }