[GR-2798] FastR Grid: window resizing improvements.

com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/shell/RCommand.java

@@ -38,6 +38,7 @@ import java.util.List;
 import com.oracle.truffle.api.interop.TruffleObject;
 import com.oracle.truffle.api.source.Source;
 import com.oracle.truffle.api.vm.PolyglotEngine;
+import com.oracle.truffle.api.vm.PolyglotEngine.Value;
 import com.oracle.truffle.r.nodes.builtin.base.Quit;
 import com.oracle.truffle.r.runtime.ExitException;
 import com.oracle.truffle.r.runtime.JumpToTopLevelException;
@@ -223,11 +224,15 @@ public class RCommand {
                     String continuePrompt = getContinuePrompt();
                     StringBuffer sb = new StringBuffer(input);
                     Source source = RSource.fromTextInternal(sb.toString(), RSource.Internal.SHELL_INPUT);
+                    boolean hasExecutor = RContext.getInstance().hasExecutor();
                     while (true) {
                         lastStatus = 0;
                         try {
                             try {
-                                vm.eval(source).get();
+                                Value val = vm.eval(source);
+                                if (hasExecutor) {
+                                    val.get();
+                                }
                                 // checked exceptions are wrapped in RuntimeExceptions
                             } catch (RuntimeException e) {
                                 if (e.getCause() instanceof com.oracle.truffle.api.vm.IncompleteSourceException) {

com.oracle.truffle.r.library/src/com/oracle/truffle/r/library/fastrGrid/WindowDevice.java

@@ -43,15 +43,30 @@ public final class WindowDevice {
 
     public static GridDevice createWindowDevice(int width, int height) {
         JFrameDevice frameDevice = JFrameDevice.create(width, height);
-        frameDevice.setResizeListener(() -> {
-            RContext.getInstance().schedule(() -> {
-                GridContext.getContext().evalInternalRFunction("redrawAll");
-            });
-        });
+        if (RContext.getInstance().hasExecutor()) {
+            frameDevice.setResizeListener(WindowDevice::redrawAll);
+        } else {
+            noSchedulingSupportWarning();
+        }
         return new BufferedJFrameDevice(frameDevice);
     }
 
     public static RError awtNotSupported() {
         throw RError.error(RError.NO_CALLER, Message.GENERIC, "AWT based grid devices are not supported.");
     }
+
+    private static void redrawAll() {
+        RContext ctx = RContext.getInstance();
+        if (ctx.hasExecutor()) {
+            // to be robust we re-check the executor availability
+            ctx.schedule(() -> {
+                GridContext.getContext().evalInternalRFunction("redrawAll");
+            });
+        }
+    }
+
+    private static void noSchedulingSupportWarning() {
+        // Note: the PolyglotEngine was not built with an Executor
+        RError.warning(RError.NO_CALLER, Message.GENERIC, "Grid cannot resize the drawings. If you resize the window, the content will be lost.");
+    }
 }

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/context/RContext.java

@@ -822,15 +822,17 @@ public final class RContext extends com.oracle.truffle.api.ExecutionContext impl
         return info.getEnv();
     }
 
+    public boolean hasExecutor() {
+        return info.executor != null;
+    }
+
     /**
-     * Allows another thread to schedule some code to be run in this context's thread. The action is
-     * ignored if the current context does not support such scheduling, i.e. the polyglot engine was
-     * not created with an executor.
+     * Allows another thread to schedule some code to be run in this context's thread. The action
+     * can be scheduled only if PolyglotEngine was created with an Executor.
      */
     public void schedule(Runnable action) {
-        if (info.executor != null) {
-            info.executor.execute(action);
-        }
+        assert hasExecutor() : "Cannot run RContext#schedule() when there is no executor.";
+        info.executor.execute(action);
     }
 
     @Override