HTML5 Drag and Drop Support (#8264)

* Add DragSource Extension (#8169)

* Add DropTarget Extension (#8170)

* Add DragStart Event to DragSource Extension (#8171)

* Make DataTransfer.dropEffect configurable (#8174)

* Make DragSource.dataTransfer data configurable (#8172)

* Add server-side Event for drop (#8177)

* Added license headers

* Extract handler methods, move DropEvent and DropListener to new file, move enums to top

* Replaced LinkedHashMap with Map and added List to preserve order of data

* Add API for adding a JS acceptance criteria for dragover and drop (#8178, #8179)

* Make DragSource Extension extendable (#8175)

* Make DropTarget Extension extendable (#8176)

* Added javadoc to protected methods

* Moved EffectAllowed to shared so that it could be used in shared state directly

* Moved DropEffect to separate file, some review fixes and javadoc

* Added list to DropTargetRpc to preserve order of data

* Remove event listeners on unregister

* Changed method names set/getData() to more descriptive set/getTransferData()

* Add server side dragStart event (#8171)

* Add style to prevent text selection to allow drag

* Remove target indicator style on drop

* Add client side dragend event listener for drag source

* Add server side dragend listener.
Attach client side listener only when server side listener added.

* Add drag source information to server side dragstart and dragend events.

* Fixed some issues addressed in review

* Trigger server side dragstart only when there is a listener attached

* Criteria script can be set as null to clear

* Use Js Interop instead of JSNI for handling event listeners

* Use elemental package instead of Js Interop for handling event listeners

* Add missing javadoc for public methods

* Add default value "uninitialized" to effectAllowed parameter

* Simple test UI for HTML5 DnD functionality (#8395)

* Add javadoc and other minor changes

6 files changed, 292 insertions, 0 deletions

diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceRpc.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceRpc.java
new file mode 100644
index 0000000000..bbad423044
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceRpc.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+import com.vaadin.shared.communication.ServerRpc;
+
+/**
+ * RPC for firing server side event when client side dragstart event happens on
+ * drag source.
+ */
+public interface DragSourceRpc extends ServerRpc {
+
+    /**
+     * Called when dragsource event happens on client side.
+     */
+    public void dragStart();
+
+    /**
+     * Called when dragend event happens on client side.
+     */
+    public void dragEnd();
+}
diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceState.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceState.java
new file mode 100644
index 0000000000..aeb4dd816b
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/DragSourceState.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.vaadin.shared.communication.SharedState;
+
+/**
+ * State class containing parameters for DragSourceExtension.
+ */
+public class DragSourceState extends SharedState {
+
+    /**
+     * Event identifier for dragend event.
+     */
+    public static final String EVENT_DRAGEND = "dragend";
+
+    /**
+     * Event identifier for dragstart event.
+     */
+    public static final String EVENT_DRAGSTART = "dragstart";
+
+    /**
+     * {@code DataTransfer.effectAllowed} parameter for the drag event.
+     */
+    public EffectAllowed effectAllowed = EffectAllowed.UNINITIALIZED;
+
+    /**
+     * {@code DataTransfer.types} parameter. Used to keep track of data formats
+     * set for the drag event.
+     */
+    public List<String> types = new ArrayList<>();
+
+    /**
+     * Used to store data in the {@code DataTransfer} object for the drag event.
+     */
+    public Map<String, String> data = new HashMap<>();
+}
diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/DropEffect.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropEffect.java
new file mode 100644
index 0000000000..5056ecfd78
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropEffect.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+/**
+ * Used to specify the drop effect to use on dragenter or dragover events.
+ */
+public enum DropEffect {
+    /**
+     * A copy of the source item is made at the new location.
+     */
+    COPY,
+
+    /**
+     * An item is moved to a new location.
+     */
+    MOVE,
+
+    /**
+     * A link is established to the source at the new location.
+     */
+    LINK,
+
+    /**
+     * The item may not be dropped.
+     */
+    NONE
+}
diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetRpc.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetRpc.java
new file mode 100644
index 0000000000..dd21278277
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetRpc.java
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+import java.util.List;
+import java.util.Map;
+
+import com.vaadin.shared.communication.ServerRpc;
+
+/**
+ * RPC for firing server side drop event when client side drop event happens on
+ * drop target.
+ */
+public interface DropTargetRpc extends ServerRpc {
+
+    /**
+     * Called when drop event happens on client side.
+     *
+     * @param types
+     *         Data types that are present in {@code data} map in the same order
+     *         as found in {@code DataTransfer.types}.
+     * @param data
+     *         Contains data from {@code DataTransfer} object.
+     * @param dropEffect
+     *         Drop effect set for the drop target where drop happened.
+     */
+    public void drop(List<String> types, Map<String, String> data,
+            DropEffect dropEffect);
+}
diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetState.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetState.java
new file mode 100644
index 0000000000..3021c0bd6b
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/DropTargetState.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+import com.vaadin.shared.communication.SharedState;
+
+/**
+ * State class containing parameters for DropTargetExtension.
+ */
+public class DropTargetState extends SharedState {
+    /**
+     * {@code DataTransfer.dropEffect} parameter for the drag event
+     */
+    public DropEffect dropEffect;
+
+    /**
+     * Criteria script to allow dragOver event on the element
+     */
+    public String dragOverCriteria;
+
+    /**
+     * Criteria script to allow drop event on the element
+     */
+    public String dropCriteria;
+}
diff --git a/shared/src/main/java/com/vaadin/shared/ui/dnd/EffectAllowed.java b/shared/src/main/java/com/vaadin/shared/ui/dnd/EffectAllowed.java
new file mode 100644
index 0000000000..2ff9f21980
--- /dev/null
+++ b/shared/src/main/java/com/vaadin/shared/ui/dnd/EffectAllowed.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.shared.ui.dnd;
+
+/**
+ * Used to specify the effect that is allowed for a drag operation.
+ */
+public enum EffectAllowed {
+    /**
+     * The item may not be dropped.
+     */
+    NONE("none"),
+
+    /**
+     * A copy of the source item may be made at the new location.
+     */
+    COPY("copy"),
+
+    /**
+     * An item may be moved to a new location.
+     */
+    MOVE("move"),
+
+    /**
+     * A link may be established to the source at the new location.
+     */
+    LINK("link"),
+
+    /**
+     * A copy or move operation is permitted.
+     */
+    COPY_MOVE("copyMove"),
+
+    /**
+     * A copy or link operation is permitted.
+     */
+    COPY_LINK("copyLink"),
+
+    /**
+     * A link or move operation is permitted.
+     */
+    LINK_MOVE("linkMove"),
+
+    /**
+     * All operations are permitted.
+     */
+    ALL("all"),
+
+    /**
+     * Default state, equivalent to ALL
+     */
+    UNINITIALIZED("uninitialized");
+
+    private final String value;
+
+    EffectAllowed(String value) {
+        this.value = value;
+    }
+
+    /**
+     * Get the string value that is accepted by the client side drag event.
+     *
+     * @return String value accepted by the client side drag event.
+     */
+    public String getValue() {
+        return value;
+    }
+}