Allow video sources to be added to Shuffleboard (#1453)

Add a Sendable wrapper for VideoSource objects.

Add convenience methods for adding video sources directly to containers
so users won't have to manually wrap video sources.

wpilibj/src/main/java/edu/wpi/first/wpilibj/shuffleboard/SendableCameraWrapper.java

@@ -0,0 +1,57 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj.shuffleboard;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+
+import edu.wpi.cscore.VideoSource;
+import edu.wpi.first.wpilibj.Sendable;
+import edu.wpi.first.wpilibj.SendableBase;
+import edu.wpi.first.wpilibj.smartdashboard.SendableBuilder;
+
+/**
+ * A wrapper to make video sources sendable and usable from Shuffleboard.
+ */
+public final class SendableCameraWrapper extends SendableBase {
+  private static final String kProtocol = "camera_server://";
+
+  private static Map<VideoSource, SendableCameraWrapper> m_wrappers = new WeakHashMap<>();
+
+  private final String m_uri;
+
+  /**
+   * Creates a new sendable wrapper. Private constructor to avoid direct instantiation with
+   * multiple wrappers floating around for the same camera.
+   *
+   * @param source the source to wrap
+   */
+  private SendableCameraWrapper(VideoSource source) {
+    super(false);
+    String name = source.getName();
+    setName(name);
+    m_uri = kProtocol + name;
+  }
+
+  /**
+   * Gets a sendable wrapper object for the given video source, creating the wrapper if one does
+   * not already exist for the source.
+   *
+   * @param source the video source to wrap
+   * @return a sendable wrapper object for the video source, usable in Shuffleboard via
+   * {@link ShuffleboardTab#add(Sendable)} and {@link ShuffleboardLayout#add(Sendable)}
+   */
+  public static SendableCameraWrapper wrap(VideoSource source) {
+    return m_wrappers.computeIfAbsent(source, SendableCameraWrapper::new);
+  }
+
+  @Override
+  public void initSendable(SendableBuilder builder) {
+    builder.addStringProperty(".ShuffleboardURI", () -> m_uri, null);
+  }
+}

wpilibj/src/main/java/edu/wpi/first/wpilibj/shuffleboard/ShuffleboardContainer.java

@@ -10,6 +10,7 @@ package edu.wpi.first.wpilibj.shuffleboard;
 import java.util.List;
 import java.util.NoSuchElementException;
 
+import edu.wpi.cscore.VideoSource;
 import edu.wpi.first.wpilibj.Sendable;
 
 /**
@@ -76,6 +77,19 @@ public interface ShuffleboardContainer extends ShuffleboardValue {
    */
   ComplexWidget add(String title, Sendable sendable) throws IllegalArgumentException;
 
+  /**
+   * Adds a widget to this container to display the given video stream.
+   *
+   * @param title    the title of the widget
+   * @param video    the video stream to display
+   * @return a widget to display the sendable data
+   * @throws IllegalArgumentException if a widget already exists in this container with the given
+   *                                  title
+   */
+  default ComplexWidget add(String title, VideoSource video) throws IllegalArgumentException {
+    return add(title, SendableCameraWrapper.wrap(video));
+  }
+
   /**
    * Adds a widget to this container to display the given sendable.
    *
@@ -86,6 +100,18 @@ public interface ShuffleboardContainer extends ShuffleboardValue {
    */
   ComplexWidget add(Sendable sendable);
 
+  /**
+   * Adds a widget to this container to display the given video stream.
+   *
+   * @param video the video to display
+   * @return a widget to display the sendable data
+   * @throws IllegalArgumentException if a widget already exists in this container with the same
+   *                                  title as the video source
+   */
+  default ComplexWidget add(VideoSource video) {
+    return add(SendableCameraWrapper.wrap(video));
+  }
+
   /**
    * Adds a widget to this container to display the given data.
    *