Don't allow non-previewable values to be previewed (#821)

Fixes #768

ui/src/main/java/edu/wpi/grip/ui/pipeline/OutputSocketController.java

@@ -1,12 +1,14 @@
 package edu.wpi.grip.ui.pipeline;
 
 import edu.wpi.grip.core.events.BenchmarkEvent;
+import edu.wpi.grip.core.events.SocketChangedEvent;
 import edu.wpi.grip.core.events.SocketPreviewChangedEvent;
 import edu.wpi.grip.core.sockets.OutputSocket;
 import edu.wpi.grip.core.sockets.Socket;
 import edu.wpi.grip.core.sockets.SocketHint;
 import edu.wpi.grip.ui.Controller;
 import edu.wpi.grip.ui.annotations.ParametrizedController;
+import edu.wpi.grip.ui.preview.ImageBasedPreviewView;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.eventbus.Subscribe;
@@ -23,6 +25,7 @@
 import javafx.scene.layout.StackPane;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static org.bytedeco.javacpp.opencv_core.Mat;
 
 /**
  * A JavaFX control that renders an {@link OutputSocket} that is the output of a step.  It shows a
@@ -34,7 +37,7 @@ public class OutputSocketController implements Controller {
 
   private final SocketHandleView.Factory socketHandleFactory;
   private final InvalidationListener previewListener;
-  private final OutputSocket socket;
+  private final OutputSocket<?> socket;
   @FXML
   private HBox root;
   @FXML
@@ -79,14 +82,43 @@ protected void initialize() {
     this.type.setText(this.socket.getSocketHint().getTypeLabel());
   }
 
-  public Socket getSocket() {
+  public Socket<?> getSocket() {
     return this.socket;
   }
 
   public SocketHandleView getHandle() {
     return this.handle;
   }
 
+  @Subscribe
+  public void onSocketChanged(SocketChangedEvent event) {
+    if (event.isRegarding(this.socket)) {
+      if (!this.socket.getValue().isPresent()) {
+        // No value
+        handlePreview(false);
+      } else if (!(this.socket.getValue().get() instanceof Mat)) {
+        // There is a non-image value, which can always be previewed
+        handlePreview(true);
+      } else {
+        // Only allow the image to be previewed if it's previewable
+        boolean previewable = this.socket.getValue()
+            .map(Mat.class::cast)
+            .map(ImageBasedPreviewView::isPreviewable)
+            .get();
+        handlePreview(previewable);
+      }
+    }
+  }
+
+  /**
+   * Disables the preview button and hides the preview if the socket value isn't able to be
+   * previewed.
+   */
+  private void handlePreview(boolean previewable) {
+    this.preview.setDisable(!previewable);
+    this.socket.setPreviewed(this.socket.isPreviewed() && previewable);
+  }
+
   @Subscribe
   public void onSocketPreviewChangedEvent(SocketPreviewChangedEvent event) {
     // Only try to update the button if the two aren't the same

ui/src/main/java/edu/wpi/grip/ui/preview/ContoursSocketPreviewView.java

@@ -3,12 +3,10 @@
 import edu.wpi.grip.core.operations.composite.ContoursReport;
 import edu.wpi.grip.core.sockets.OutputSocket;
 import edu.wpi.grip.ui.util.GripPlatform;
-import edu.wpi.grip.ui.util.ImageConverter;
 
 import javafx.scene.control.CheckBox;
 import javafx.scene.control.Label;
 import javafx.scene.image.Image;
-import javafx.scene.image.ImageView;
 import javafx.scene.layout.VBox;
 
 import static org.bytedeco.javacpp.opencv_core.CV_8UC3;
@@ -32,8 +30,6 @@ public final class ContoursSocketPreviewView extends ImageBasedPreviewView<Conto
       Scalar.BLUE,
       Scalar.MAGENTA,
   };
-  private final ImageConverter imageConverter = new ImageConverter();
-  private final ImageView imageView = new ImageView();
   private final Label infoLabel = new Label();
   private final CheckBox colorContours;
   private final Mat tmp = new Mat();

ui/src/main/java/edu/wpi/grip/ui/preview/ImageBasedPreviewView.java

@@ -9,6 +9,10 @@
 import javafx.application.Platform;
 import javafx.scene.image.ImageView;
 
+import static org.bytedeco.javacpp.opencv_core.CV_8S;
+import static org.bytedeco.javacpp.opencv_core.CV_8U;
+import static org.bytedeco.javacpp.opencv_core.Mat;
+
 /**
  * Base class for image previews.
  */
@@ -47,6 +51,18 @@ protected final int getImageHeight() {
    */
   protected abstract void convertImage();
 
+  /**
+   * Checks if an image is able to be previewed.
+   *
+   * @param image the image to check
+   *
+   * @return true if the image can be previewed, false if it can't
+   */
+  public static boolean isPreviewable(Mat image) {
+    return (image.channels() == 1) || (image.channels() == 3)
+        && (image.depth() == CV_8U || image.depth() == CV_8S);
+  }
+
   /**
    * Updates the image preview when the pipeline runs.
    */

ui/src/main/java/edu/wpi/grip/ui/preview/ImageSocketPreviewView.java

@@ -26,12 +26,14 @@ public class ImageSocketPreviewView extends ImageBasedPreviewView<Mat> {
   @Override
   protected void convertImage() {
     synchronized (this) {
-      this.getSocket().getValue().ifPresent(mat -> {
-        platform.runAsSoonAsPossible(() -> {
-          Image image = imageConverter.convert(mat, getImageHeight());
-          imageView.setImage(image);
-        });
-      });
+      this.getSocket().getValue()
+          .filter(ImageBasedPreviewView::isPreviewable)
+          .ifPresent(mat -> {
+            platform.runAsSoonAsPossible(() -> {
+              Image image = imageConverter.convert(mat, getImageHeight());
+              imageView.setImage(image);
+            });
+          });
     }
   }
 }