change fence query

src/main/java/me/cortex/voxy/client/core/gl/GlFence.java

@@ -1,6 +1,7 @@
 package me.cortex.voxy.client.core.gl;
 
 import me.cortex.voxy.common.util.TrackedObject;
+import org.lwjgl.system.MemoryUtil;
 
 import static org.lwjgl.opengl.GL32.*;
 
@@ -12,13 +13,24 @@ public class GlFence extends TrackedObject {
         this.fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
     }
 
+    private static final long SCRATCH = MemoryUtil.nmemCalloc(1,4);
+
     public boolean signaled() {
         if (!this.signaled) {
+            /*
             int ret = glClientWaitSync(this.fence, 0, 0);
             if (ret == GL_ALREADY_SIGNALED || ret == GL_CONDITION_SATISFIED) {
                 this.signaled = true;
             } else if (ret != GL_TIMEOUT_EXPIRED) {
                 throw new IllegalStateException("Poll for fence failed, glError: " + glGetError());
+            }*/
+            MemoryUtil.memPutInt(SCRATCH, -1);
+            nglGetSynciv(this.fence, GL_SYNC_STATUS, 1, 0, SCRATCH);
+            int val = MemoryUtil.memGetInt(SCRATCH);
+            if (val == GL_SIGNALED) {
+                this.signaled = true;
+            } else if (val != GL_UNSIGNALED) {
+                throw new IllegalStateException("Unknown data from glGetSync: "+val);
             }
         }
         return this.signaled;