From 69b43cb346b504d713e458b987e65f4db1b825df Mon Sep 17 00:00:00 2001
From: Pekka Hyvönen <pekka@vaadin.com>
Date: Mon, 20 Mar 2017 16:04:56 +0200
Subject: Initial documentation for 8.1 Drag and Drop (#8867)

* Initial documentation for 8.1 Drag and Drop

Part of #8395
---
 documentation/advanced/advanced-dragndrop.asciidoc | 563 +++------------------
 1 file changed, 66 insertions(+), 497 deletions(-)

(limited to 'documentation/advanced/advanced-dragndrop.asciidoc')

diff --git a/documentation/advanced/advanced-dragndrop.asciidoc b/documentation/advanced/advanced-dragndrop.asciidoc
index 814883357f..8c9124f6d7 100644
--- a/documentation/advanced/advanced-dragndrop.asciidoc
+++ b/documentation/advanced/advanced-dragndrop.asciidoc
@@ -9,550 +9,118 @@ layout: page
 
 ((("Drag and Drop", id="term.advanced.dragndrop", range="startofrange")))
 
+IMPORTANT: This feature is currently being developed and only available in the Framework 8.1 prerelease versions, starting from 8.1.0.alpha1.
 
 Dragging an object from one location to another by grabbing it with mouse,
 holding the mouse button pressed, and then releasing the button to "drop" it to
 the other location is a common way to move, copy, or associate objects. For
 example, most operating systems allow dragging and dropping files between
-folders or dragging a document on a program to open it. In Vaadin, it is
-possible to drag and drop components and parts of certain components.
-
-Dragged objects, or __transferables__, are essentially data objects. You can
-drag and drop rows in [classname]#Table# and nodes in [classname]#Tree#
-components, either within or between the components. You can also drag entire
-components by wrapping them inside [classname]#DragAndDropWrapper#.
-
-Dragging starts from a __drag source__, which defines the transferable.
-Transferables implement the [classname]#Transferable# interfaces. For trees and
-tables, which are bound to [classname]#Container# data sources, a node or row
-transferable is a reference to an [classname]#Item# in the Vaadin Data Model.
-Dragged components are referenced with a [classname]#WrapperTransferable#.
-Starting dragging does not require any client-server communication, you only
-need to enable dragging. All drag and drop logic occurs in two operations:
-determining ( __accepting__) where dropping is allowed and actually dropping.
-Drops can be done on a __drop target__, which implements the
-[classname]#DropTarget# interface. Three components implement the interface:
-[classname]#Tree#, [classname]#Table#, and [classname]#DragAndDropWrapper#.
-These accept and drop operations need to be provided in a __drop handler__.
-Essentially all you need to do to enable drag and drop is to enable dragging in
-the drag source and implement the [methodname]#getAcceptCriterion()# and
-[methodname]#drop()# methods in the [classname]#DropHandler# interface.
-
-The client-server architecture of Vaadin causes special requirements for the
-drag and drop functionality. The logic for determining where a dragged object
-can be dropped, that is, __accepting__ a drop, should normally be done on the
-client-side, in the browser. Server communications are too slow to have much of
-such logic on the server-side. The drag and drop feature therefore offers a
-number of ways to avoid the server communications to ensure a good user
-experience.
+folders or dragging a document on a program to open it. Framework version 8.1 adds support for https://developer.mozilla.org/en-US/docs/Web/API/HTML_Drag_and_Drop_API[HTML5 drag and drop] features. This makes it possible to set components as drag sources that user can drag and drop, or to set them as drop targets to drop things on.
 
-[[advanced.dragndrop.drophandler]]
-== Handling Drops
-
-Most of the user-defined drag and drop logic occurs in a __drop handler__, which
-is provided by implementing the [methodname]#drop()# method in the
-[classname]#DropHandler# interface. A closely related definition is the drop
-accept criterion, which is defined in the [methodname]#getAcceptCriterion()#
-method in the same interface. It is described in
-<<advanced.dragndrop.acceptcriteria>> later.
-
-The [methodname]#drop()# method gets a [classname]#DragAndDropEvent# as its
-parameters. The event object provides references to two important object:
-[classname]#Transferable# and [classname]#TargetDetails#.
-
-A [classname]#Transferable# contains a reference to the object (component or
-data item) that is being dragged. A tree or table item is represented as a
-[classname]#TreeTransferable# or [classname]#TableTransferable# object, which
-carries the item identifier of the dragged tree or table item. These special
-transferables, which are bound to some data in a container, are
-[classname]#DataBoundTransferable#. Dragged components are represented as
-[classname]#WrapperTransferable# objects, as the components are wrapped in a
-[classname]#DragAndDropWrapper#.
-
-The [classname]#TargetDetails# object provides information about the exact
-location where the transferable object is being dropped. The exact class of the
-details object depends on the drop target and you need to cast it to the proper
-subclass to get more detailed information. If the target is selection component,
-essentially a tree or a table, the [classname]#AbstractSelectTargetDetails#
-object tells the item on which the drop is being made. For trees, the
-[classname]#TreeTargetDetails# gives some more details. For wrapped components,
-the information is provided in a [classname]#WrapperDropDetails# object. In
-addition to the target item or component, the details objects provide a __drop
-location__. For selection components, the location can be obtained with the
-[methodname]#getDropLocation()# and for wrapped components with
-[methodname]#verticalDropLocation()# and [methodname]#horizontalDropLocation()#.
-The locations are specified as either [classname]#VerticalDropLocation# or
-[classname]#HorizontalDropLocation# objects. The drop location objects specify
-whether the transferable is being dropped above, below, or directly on (at the
-middle of) a component or item.
-
-Dropping on a [classname]#Tree#, [classname]#Table#, and a wrapped component is
-explained further in the following sections.
-
-
-[[advanced.dragndrop.treedrop]]
-== Dropping Items On a [classname]#Tree#
-
-You can drag items from, to, or within a [classname]#Tree#. Making tree a drag
-source requires simply setting the drag mode with [methodname]#setDragMode()#.
-[classname]#Tree# currently supports only one drag mode,
-[literal]#++TreeDragMode.NODE++#, which allows dragging single tree nodes. While
-dragging, the dragged node is referenced with a [classname]#TreeTransferable#
-object, which is a [classname]#DataBoundTransferable#. The tree node is
-identified by the item ID of the container item.
-
-When a transferable is dropped on a tree, the drop location is stored in a
-[classname]#TreeTargetDetails# object, which identifies the target location by
-item ID of the tree node on which the drop is made. You can get the item ID with
-[methodname]#getItemIdOver()# method in
-[classname]#AbstractSelectTargetDetails#, which the
-[classname]#TreeTargetDetails# inherits. A drop can occur directly on or above
-or below a node; the exact location is a [classname]#VerticalDropLocation#,
-which you can get with the [methodname]#getDropLocation()# method.
-
-In the example below, we have a [classname]#Tree# and we allow reordering the
-tree items by drag and drop.
+== Drag Source
 
+Any component can be made a drag source that has a set of data that is transferred when it is dragged and dropped. 
 
-[source, java]
-----
-final Tree tree = new Tree("Inventory");
-tree.setContainerDataSource(TreeExample.createTreeContent());
-layout.addComponent(tree);
-        
-// Expand all items
-for (Iterator<?> it = tree.rootItemIds().iterator(); it.hasNext();)
-    tree.expandItemsRecursively(it.next());
-        
-// Set the tree in drag source mode
-tree.setDragMode(TreeDragMode.NODE);
-        
-// Allow the tree to receive drag drops and handle them
-tree.setDropHandler(new DropHandler() {
-    public AcceptCriterion getAcceptCriterion() {
-        return AcceptAll.get();
-    }
+To make a component a drag source, you apply the [classname]#DragSourceExtension# to it. Then you can define the data to transfer, and the allowed drag effect.
 
-    public void drop(DragAndDropEvent event) {
-        // Wrapper for the object that is dragged
-        Transferable t = event.getTransferable();
-        
-        // Make sure the drag source is the same tree
-        if (t.getSourceComponent() != tree)
-            return;
-        
-        TreeTargetDetails target = (TreeTargetDetails)
-            event.getTargetDetails();
-
-        // Get ids of the dragged item and the target item
-        Object sourceItemId = t.getData("itemId");
-        Object targetItemId = target.getItemIdOver();
-
-        // On which side of the target the item was dropped 
-        VerticalDropLocation location = target.getDropLocation();
-        
-        HierarchicalContainer container = (HierarchicalContainer)
-        tree.getContainerDataSource();
-
-        // Drop right on an item -> make it a child
-        if (location == VerticalDropLocation.MIDDLE)
-            tree.setParent(sourceItemId, targetItemId);
-
-        // Drop at the top of a subtree -> make it previous
-        else if (location == VerticalDropLocation.TOP) {
-            Object parentId = container.getParent(targetItemId);
-            container.setParent(sourceItemId, parentId);
-            container.moveAfterSibling(sourceItemId, targetItemId);
-            container.moveAfterSibling(targetItemId, sourceItemId);
-        }
-        
-        // Drop below another item -> make it next 
-        else if (location == VerticalDropLocation.BOTTOM) {
-            Object parentId = container.getParent(targetItemId);
-            container.setParent(sourceItemId, parentId);
-            container.moveAfterSibling(sourceItemId, targetItemId);
-        }
-    }
-});
-----
-
-[[advanced.dragndrop.treedrop.criteria]]
-=== Accept Criteria for Trees
-
-[classname]#Tree# defines some specialized accept criteria for trees.
-
-[classname]#TargetInSubtree#(client-side):: Accepts if the target item is in the specified sub-tree. The sub-tree is specified by the item ID of the root of the sub-tree in the constructor. The second constructor includes a depth parameter, which specifies how deep from the given root node are drops accepted. Value [literal]#++-1++# means infinite, that is, the entire sub-tree, and is therefore the same as the simpler constructor.
-[classname]#TargetItemAllowsChildren#(client-side):: Accepts a drop if the tree has [methodname]#setChildrenAllowed()# enabled for the target item. The criterion does not require parameters, so the class is a singleton and can be acquired with [methodname]#Tree.TargetItemAllowsChildren.get()#. For example, the following composite criterion accepts drops only on nodes that allow children, but between all nodes: 
-+
 [source, java]
 ----
-return new Or (Tree.TargetItemAllowsChildren.get(), new Not(VerticalLocationIs.MIDDLE));
-----
-
-[classname]#TreeDropCriterion#(server-side):: Accepts drops on only some items, which as specified by a set of item IDs. You must extend the abstract class and implement the [methodname]#getAllowedItemIds()# to return the set. While the criterion is server-side, it is lazy-loading, so that the list of accepted target nodes is loaded only once from the server for each drag operation. See <<advanced.dragndrop.acceptcriteria>> for an example.
-
-
-In addition, the accept criteria defined in [classname]#AbstractSelect# are
-available for a [classname]#Tree#, as listed in
-<<advanced.dragndrop.acceptcriteria>>.
-
-
+Label draggableLabel = new Label("You can grab and drag me");
+DragSourceExtension<Label> dragSource = new DragSourceExtension<>(draggableLabel);
 
-[[advanced.dragndrop.tabledrop]]
-== Dropping Items On a [classname]#Table#
-
-You can drag items from, to, or within a [classname]#Table#. Making table a drag
-source requires simply setting the drag mode with [methodname]#setDragMode()#.
-[classname]#Table# supports dragging both single rows, with
-[literal]#++TableDragMode.ROW++#, and multiple rows, with
-[literal]#++TableDragMode.MULTIROW++#. While dragging, the dragged node or nodes
-are referenced with a [classname]#TreeTransferable# object, which is a
-[classname]#DataBoundTransferable#. Tree nodes are identified by the item IDs of
-the container items.
-
-When a transferable is dropped on a table, the drop location is stored in a
-[classname]#AbstractSelectTargetDetails# object, which identifies the target row
-by its item ID. You can get the item ID with [methodname]#getItemIdOver()#
-method. A drop can occur directly on or above or below a row; the exact location
-is a [classname]#VerticalDropLocation#, which you can get with the
-[methodname]#getDropLocation()# method from the details object.
-
-[[advanced.dragndrop.tabledrop.criteria]]
-=== Accept Criteria for Tables
-
-[classname]#Table# defines one specialized accept criterion for tables.
-
-[classname]#TableDropCriterion#(server-side):: Accepts drops only on (or above or below) items that are specified by a set of item IDs. You must extend the abstract class and implement the [methodname]#getAllowedItemIds()# to return the set. While the criterion is server-side, it is lazy-loading, so that the list of accepted target items is loaded only once from the server for each drag operation.
-
-
-
-
-[[advanced.dragndrop.acceptcriteria]]
-== Accepting Drops
-
-((("Drag and Drop", "Accept Criteria", id="term.advanced.dragndrop.acceptcriteria", range="startofrange")))
-
-
-You can not drop the objects you are dragging around just anywhere. Before a
-drop is possible, the specific drop location on which the mouse hovers must be
-__accepted__. Hovering a dragged object over an accepted location displays an
-__accept indicator__, which allows the user to position the drop properly. As
-such checks have to be done all the time when the mouse pointer moves around the
-drop targets, it is not feasible to send the accept requests to the server-side,
-so drops on a target are normally accepted by a client-side __accept
-criterion__.
-
-A drop handler must define the criterion on the objects which it accepts to be
-dropped on the target. The criterion needs to be provided in the
-[classname]#getAcceptCriterion()# method of the [classname]#DropHandler#
-interface. A criterion is represented in an [classname]#AcceptCriterion# object,
-which can be a composite of multiple criteria that are evaluated using logical
-operations. There are two basic types of criteria: __client-side__ and
-__server-side criteria__. The various built-in criteria allow accepting drops
-based on the identity of the source and target components, and on the __data
-flavor__ of the dragged objects.
-
-To allow dropping any transferable objects, you can return a universal accept
-criterion, which you can get with [methodname]#AcceptAll.get()#.
-
-
-[source, java]
-----
-tree.setDropHandler(new DropHandler() {
-    public AcceptCriterion getAcceptCriterion() {
-        return AcceptAll.get();
-    }
-    ...
+// set the allowed effect
+dragSource.setEffectAllowed(EffectAllowed.MOVE);
+// set the data to transfer
+dragSource.setTransferData("text/plain", "hello receiver");
 ----
 
-[[advanced.dragndrop.acceptcriteria.client-side]]
-=== Client-Side Criteria
-
-The __client-side criteria__, which inherit the
-[classname]#ClientSideCriterion#, are verified on the client-side, so server
-requests are not needed for verifying whether each component on which the mouse
-pointer hovers would accept a certain object.
-
-The following client-side criteria are define in
-[package]#com.vaadin.event.dd.acceptcriterion#:
+The __effect allowed__ specifies the allowed effects that must match the __drop effect__ of the drop target. If these don't match, the drop event is never fired on the target. If multiple effects are allowed, the user can use the modifier keys to switch between the desired effects. The default effect and the modifier keys are system and browser dependent.
 
-[classname]#AcceptAll#:: Accepts all transferables and targets.
-[classname]#And#:: Performs the logical AND operation on two or more client-side criteria; accepts the transferable if all the given sub-criteria accept it.
-[classname]#ContainsDataFlavour#:: The transferable must contain the defined data flavour.
-[classname]#Not#:: Performs the logical NOT operation on a client-side criterion; accepts the transferable if and only if the sub-criterion does not accept it.
-[classname]#Or#:: Performs the logical OR operation on two or more client-side criteria; accepts the transferable if any of the given sub-criteria accepts it.
-[classname]#SourceIs#:: Accepts all transferables from any of the given source components
-[classname]#SourceIsTarget#:: Accepts the transferable only if the source component is the same as the target. This criterion is useful for ensuring that items are dragged only within a tree or a table, and not from outside it.
-[classname]#TargetDetailIs#:: Accepts any transferable if the target detail, such as the item of a tree node or table row, is of the given data flavor and has the given value.
+The __transfer data__ is a set of data, that the drop target will receive in the __drop event__. The first parameter given is the type of the data, and the second parameter is the actual data as string. The type parameter thus acts as a key for the actual data. For more information about the
+type parameter, see https://developer.mozilla.org/en-US/docs/Web/API/HTML_Drag_and_Drop_API/Recommended_drag_types[MDN recommendations].
 
+The [classname]#DragStartEvent# is fired when the drag has started, and the [classname]#DragEndEvent# event when the drag has ended, either in a drop or a cancel.
 
-In addition, target components such as [classname]#Tree# and [classname]#Table#
-define some component-specific client-side accept criteria. See
-<<advanced.dragndrop.treedrop>> for more details.
-
-[classname]#AbstractSelect# defines the following criteria for all selection
-components, including [classname]#Tree# and [classname]#Table#.
-
-[classname]#AcceptItem#:: Accepts only specific items from a specific selection component. The selection component, which must inherit [classname]#AbstractSelect#, is given as the first parameter for the constructor. It is followed by a list of allowed item identifiers in the drag source.
-[classname]#AcceptItem.ALL#:: Accepts all transferables as long as they are items.
-[classname]#TargetItemIs#:: Accepts all drops on the specified target items. The constructor requires the target component ( [classname]#AbstractSelect#) followed by a list of allowed item identifiers.
-[classname]#VerticalLocationIs.MIDDLE#, [classname]#TOP#, and [classname]#BOTTOM#:: The three static criteria accepts drops on, above, or below an item. For example, you could accept drops only in between items with the following: 
 [source, java]
 ----
-public AcceptCriterion getAcceptCriterion() {
-    return new Not(VerticalLocationIs.MIDDLE);
-}
+dragSource.addDragStartListener(event ->
+    event.getComponent().addStyleName("dragged")
+);
+dragSource.addDragEndListener(event -> 
+    event.getComponent().removeStyleName("dragged")
+);
 ----
 
-
-
-
-
-[[advanced.dragndrop.acceptcriteria.server-side]]
-=== Server-Side Criteria
-
-The __server-side criteria__ are verified on the server-side with the
-[methodname]#accept()# method of the [classname]#ServerSideCriterion# class.
-This allows fully programmable logic for accepting drops, but the negative side
-is that it causes a very large amount of server requests. A request is made for
-every target position on which the pointer hovers. This problem is eased in many
-cases by the component-specific lazy loading criteria
-[classname]#TableDropCriterion# and [classname]#TreeDropCriterion#. They do the
-server visit once for each drag and drop operation and return all accepted rows
-or nodes for current [classname]#Transferable# at once.
-
-The [methodname]#accept()# method gets the drag event as a parameter so it can
-perform its logic much like in [methodname]#drop()#.
-
-
-[source, java]
-----
-public AcceptCriterion getAcceptCriterion() {
-    // Server-side accept criterion that allows drops on any other
-    // location except on nodes that may not have children
-    ServerSideCriterion criterion = new ServerSideCriterion() {
-        public boolean accept(DragAndDropEvent dragEvent) {
-            TreeTargetDetails target = (TreeTargetDetails)
-                dragEvent.getTargetDetails();
-
-            // The tree item on which the load hovers
-            Object targetItemId = target.getItemIdOver();
-
-            // On which side of the target the item is hovered
-            VerticalDropLocation location = target.getDropLocation();
-            if (location == VerticalDropLocation.MIDDLE)
-                if (! tree.areChildrenAllowed(targetItemId))
-                    return false; // Not accepted
-
-            return true; // Accept everything else
-        }
-    };
-    return criterion;
-}
-----
-
-The server-side criteria base class [classname]#ServerSideCriterion# provides a
-generic [methodname]#accept()# method. The more specific
-[classname]#TableDropCriterion# and [classname]#TreeDropCriterion# are
-conveniency extensions that allow definiting allowed drop targets as a set of
-items. They also provide some optimization by lazy loading, which reduces server
-communications significantly.
-
-
-[source, java]
+[NOTE]
+====
+The browsers allow the user to select and drag and drop text, which may cause some issues when trying to drag a component that has text. You can fix this by setting the following style rule to the drag source component to prevent dragging of the text instead of the whole component.
+[source, css]
 ----
-public AcceptCriterion getAcceptCriterion() {
-    // Server-side accept criterion that allows drops on any
-    // other tree node except on node that may not have children
-    TreeDropCriterion criterion = new TreeDropCriterion() {
-        @Override
-        protected Set<Object> getAllowedItemIds(
-                DragAndDropEvent dragEvent, Tree tree) {
-            HashSet<Object> allowed = new HashSet<Object>();
-            for (Iterator<Object> i =
-                   tree.getItemIds().iterator(); i.hasNext();) {
-                Object itemId = i.next();
-                if (tree.hasChildren(itemId))
-                    allowed.add(itemId);
-            }
-            return allowed;
-        }
-    };
-    return criterion;
-}
+user-select: none;
 ----
+====
 
+[[advanced.dragndrop.drophandler]]
+== Drop Target
 
-[[advanced.dragndrop.acceptcriteria.indicators]]
-=== Accept Indicators
-
-When a dragged object hovers on a drop target, an __accept indicator__ is
-displayed to show whether or not the location is accepted. For
-[parameter]#MIDDLE# location, the indicator is a box around the target (tree
-node, table row, or component). For vertical drop locations, the accepted
-locations are shown as horizontal lines, and for horizontal drop locations as
-vertical lines.
-
-For [classname]#DragAndDropWrapper# drop targets, you can disable the accept
-indicators or __drag hints__ with the [parameter]#no-vertical-drag-hints#,
-[parameter]#no-horizontal-drag-hints#, and [parameter]#no-box-drag-hints#
-styles. You need to add the styles to the __layout that contains__ the wrapper,
-not to the wrapper itself.
+The drag operations end when the mouse button is released on a valid drop target. It is then up to the target to react to the drop event and the data associated with the drag, set by the drag source.
 
+To make a component be a drop target, you apply the [classname]#DropTargetExtension# to it. The extension allows you to control when the drop is acceptable and then react to the drop event.
 
 [source, java]
 ----
-// Have a wrapper
-DragAndDropWrapper wrapper = new DragAndDropWrapper(c);
-layout.addComponent(wrapper);
-
-// Disable the hints
-layout.addStyleName("no-vertical-drag-hints");
-layout.addStyleName("no-horizontal-drag-hints");
-layout.addStyleName("no-box-drag-hints");
-----
+VerticalLayout dropTargetLayout = new VerticalLayout();
+dropTargetLayout.setCaption("Drop things inside me");
+dropTargetLayout.addStyleName(ValoTheme.LAYOUT_CARD);
 
+// make the layout accept drops
+DropTargetExtension<VerticalLayout> dropTarget = new DropTargetExtension<>(dropTargetLayout);
 
-(((range="endofrange", startref="term.advanced.dragndrop.acceptcriteria")))
-
-[[advanced.dragndrop.dragging]]
-== Dragging Components
-
-Dragging a component requires wrapping the source component within a
-[classname]#DragAndDropWrapper#. You can then allow dragging by putting the
-wrapper (and the component) in drag mode with [methodname]#setDragStartMode()#.
-The method supports two drag modes: [parameter]#DragStartMode.WRAPPER# and
-[parameter]#DragStartMode.COMPONENT#, which defines whether the entire wrapper
-is shown as the drag image while dragging or just the wrapped component.
-
-
-[source, java]
-----
-// Have a component to drag
-final Button button = new Button("An Absolute Button");
-
-// Put the component in a D&D wrapper and allow dragging it
-final DragAndDropWrapper buttonWrap = new DragAndDropWrapper(button);
-buttonWrap.setDragStartMode(DragStartMode.COMPONENT);
+// the drop effect must match the allowed effect in the drag source for a successful drop
+dropTarget.setDropEffect(DropEffect.MOVE);
 
-// Set the wrapper to wrap tightly around the component
-buttonWrap.setSizeUndefined();
+// catch the drops
+dropTarget.addDropListener(event -> {
+    // if the drag source is in the same UI as the target
+    Optional<AbstractComponent> dragSource = event.getDragSourceComponent();
+    if (dragSource.isPresent() && dragSource.get() instanceof Label) {
+        // move the label to the layout
+        dropTargetLayout.addComponent(dragSource.get());
         
-// Add the wrapper, not the component, to the layout
-layout.addComponent(buttonWrap, "left: 50px; top: 50px;");
-----
-
-The default height of [classname]#DragAndDropWrapper# is undefined, but the
-default width is 100%. If you want to ensure that the wrapper fits tightly
-around the wrapped component, you should call [methodname]#setSizeUndefined()#
-for the wrapper. Doing so, you should make sure that the wrapped component does
-not have a relative size, which would cause a paradox.
-
-Dragged components are referenced in the [classname]#WrapperTransferable#. You
-can get the reference to the dragged component with
-[methodname]#getDraggedComponent()#. The method will return [literal]#++null++#
-if the transferable is not a component. Also HTML 5 drags (see later) are held
-in wrapper transferables.
-
-
-[[advanced.dragndrop.drop-on-component]]
-== Dropping on a Component
-
-Drops on a component are enabled by wrapping the component in a
-[classname]#DragAndDropWrapper#. The wrapper is an ordinary component; the
-constructor takes the wrapped component as a parameter. You just need to define
-the [classname]#DropHandler# for the wrapper with
-[methodname]#setDropHandler()#.
-
-In the following example, we allow moving components in an absolute layout.
-Details on the drop handler are given later.
-
-
-[source, java]
-----
-// A layout that allows moving its contained components
-// by dragging and dropping them
-final AbsoluteLayout absLayout = new AbsoluteLayout();
-absLayout.setWidth("100%");
-absLayout.setHeight("400px");
-
-... put some (wrapped) components in the layout ...
-
-// Wrap the layout to allow handling drops
-DragAndDropWrapper layoutWrapper =
-        new DragAndDropWrapper(absLayout);
-
-// Handle moving components within the AbsoluteLayout
-layoutWrapper.setDropHandler(new DropHandler() {
-    public AcceptCriterion getAcceptCriterion() {
-        return AcceptAll.get();
-    }
-    
-    public void drop(DragAndDropEvent event) {
-        ...        
+        // get possible transfer data
+        // NOTE that "text" is same as "text/plain" from drag source data,
+        // see the HTML5 standard for more info
+        String message = event.getTransferData("text");
+        Notification.show("DropEvent with data transfer: "+ message);
     }
 });
 ----
 
-[[advanced.dragndrop.drop-on-component.details]]
-=== Target Details for Wrapped Components
-
-The drop handler receives the drop target details in a
-[classname]#WrapperTargetDetails# object, which implements the
-[classname]#TargetDetails# interface.
-
-
-[source, java]
-----
-public void drop(DragAndDropEvent event) {
-    WrapperTransferable t =
-        (WrapperTransferable) event.getTransferable();
-    WrapperTargetDetails details =
-        (WrapperTargetDetails) event.getTargetDetails();
-----
-
-The wrapper target details include a [classname]#MouseEventDetails# object,
-which you can get with [methodname]#getMouseEvent()#. You can use it to get the
-mouse coordinates for the position where the mouse button was released and the
-drag ended. Similarly, you can find out the drag start position from the
-transferable object (if it is a [classname]#WrapperTransferable#) with
-[methodname]#getMouseDownEvent()#.
+When data is dragged over a drop target, the __v-drag-over__ class name is applied to the root element of the drop target component automatically.
 
+=== Controlling When The Drop is Acceptable
 
-[source, java]
-----
-// Calculate the drag coordinate difference
-int xChange = details.getMouseEvent().getClientX()
-              - t.getMouseDownEvent().getClientX();
-int yChange = details.getMouseEvent().getClientY()
-              - t.getMouseDownEvent().getClientY();
-
-// Move the component in the absolute layout
-ComponentPosition pos =
-    absLayout.getPosition(t.getSourceComponent());
-pos.setLeftValue(pos.getLeftValue() + xChange);
-pos.setTopValue(pos.getTopValue() + yChange);
-----
+The __drop effect__ allows you to specify the desired drop effect, and for a succesful drop it must match the allowed effect that has been set for the drag source. Note that you can allow multiple effects, and that you should not rely on the default effect since it may vary between browsers.
 
-You can get the absolute x and y coordinates of the target wrapper with
-[methodname]#getAbsoluteLeft()# and [methodname]#getAbsoluteTop()#, which allows
-you to translate the absolute mouse coordinates to coordinates relative to the
-wrapper. Notice that the coordinates are really the position of the wrapper, not
-the wrapped component; the wrapper reserves some space for the accept
-indicators.
+The __drag over criteria__ allows you determine whether the current drag source is allowed as a drop target, when the source is moved on top of the target. It is a script that is executed always when the `dragover` event is fired for the first time for this source, and returning `false` will prevent showing any drop effect. The script gets the `dragover` event as a parameter named `event`.
 
-The [methodname]#verticalDropLocation()# and
-[methodname]#horizontalDropLocation()# return the more detailed drop location in
-the target.
+The __drop criteria__ is similar to __drag over criteria__, but it is executed when the user has dropped the data by releasing the mouse button. The script gets the `drop` event as a parameter named `event`. Returning `false` will prevent the drop and no drop event is fired on the server side.
 
+////
+TODO Add an example of drag over criteria and drop criteria
+////
 
+=== 
 
+////
+TODO add back when supported with new API ?
 [[advanced.dragndrop.external]]
 == Dragging Files from Outside the Browser
 
-The [classname]#DragAndDropWrapper# allows dragging files from outside the
-browser and dropping them on a component wrapped in the wrapper. Dropped files
-are automatically uploaded to the application and can be acquired from the
+The [classname]#DropTargetExtension# allows dragging files from outside the
+browser and dropping them on a target component.
+
+Dropped files are automatically uploaded to the application and can be acquired from the
 wrapper with [methodname]#getFiles()#. The files are represented as
 [classname]#Html5File# objects as defined in the inner class. You can define an
 upload [classname]#Receiver# to receive the content of a file to an
@@ -561,6 +129,7 @@ upload [classname]#Receiver# to receive the content of a file to an
 Dragging and dropping files to browser is supported in HTML 5 and requires a
 compatible browser, such as Mozilla Firefox 3.6 or newer.
 
+////
 
 (((range="endofrange", startref="term.advanced.dragndrop")))
 
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