Improved drag&drop behavior

ide/app/lib/ui/files_controller.dart

@@ -242,6 +242,23 @@ class FilesController implements TreeViewDelegate {
     }
   }
 
+  String treeViewDropCellsEffect(TreeView view,
+                                 List<String> nodesUIDs,
+                                 String nodeUID) {
+    if (nodeUID == null) {
+      return "none";
+    }
+    if (_isDifferentProject(nodesUIDs, nodeUID)) {
+      return "copy";
+    } else {
+      if (_isValidMove(nodesUIDs, nodeUID)) {
+        return "move";
+      } else {
+        return "none";
+      }
+    }
+  }
+
   void treeViewDrop(TreeView view, String nodeUID, html.DataTransfer dataTransfer) {
     Folder destinationFolder = _filesMap[nodeUID] as Folder;
     for(html.File file in dataTransfer.files) {
@@ -254,6 +271,23 @@ class FilesController implements TreeViewDelegate {
       reader.readAsArrayBuffer(file);
     }
   }
+
+  bool _isDifferentProject(List<String> nodesUIDs, String targetNodeUID) {
+    if (targetNodeUID == null) {
+      return false;
+    }
+    Resource destination = _filesMap[targetNodeUID];
+    Project destinationProject = destination is Project ? destination :
+        destination.project;
+    for(String nodeUID in nodesUIDs) {
+      Resource node = _filesMap[nodeUID];
+      // Check if the resource have the same top-level container.
+      if (node.project == destinationProject) {
+        return false;
+      }
+    }
+    return true;
+  }
 
   // Returns true if the move is valid:
   // - We don't allow moving a file to its parent since it's a no-op.
@@ -300,16 +334,31 @@ class FilesController implements TreeViewDelegate {
   void treeViewDropCells(TreeView view,
                          List<String> nodesUIDs,
                          String targetNodeUID) {
-    Resource destination = _filesMap[targetNodeUID];
-    if (_isValidMove(nodesUIDs, targetNodeUID)) {
-      _workspace.moveTo(nodesUIDs.map((f) => _filesMap[f]).toList(), destination);
+    Folder destination = _filesMap[targetNodeUID] as Folder;
+    if (_isDifferentProject(nodesUIDs, targetNodeUID)) {
+      List<Future> futures = [];
+      for(String nodeUID in nodesUIDs) {
+        Resource res = _filesMap[nodeUID];
+        futures.add(destination.importResource(res));
+      }
+      Future.wait(futures).catchError((e) {
+        _delegate.showErrorMessage('Error while importing files', e);
+      });
+    } else {
+      if (_isValidMove(nodesUIDs, targetNodeUID)) {
+        _workspace.moveTo(nodesUIDs.map((f) => _filesMap[f]).toList(), destination);
+      }
     }
   }
 
   bool treeViewAllowsDropCells(TreeView view,
                                List<String> nodesUIDs,
                                String destinationNodeUID) {
-    return _isValidMove(nodesUIDs, destinationNodeUID);
+    if (_isDifferentProject(nodesUIDs, destinationNodeUID)) {
+      return true;
+    } else {
+      return _isValidMove(nodesUIDs, destinationNodeUID);
+    }
   }
 
   bool treeViewAllowsDrop(TreeView view,

ide/app/lib/ui/files_controller_delegate.dart

@@ -32,4 +32,9 @@ abstract class FilesControllerDelegate {
    * [resource].
    */
   List<ContextAction> getActionsFor(List<Resource> resources);
+
+  /**
+   * The implementation of this method should report an error.
+   */
+   void showErrorMessage(String title, String message);
 }

ide/app/lib/ui/widgets/treeview.dart

@@ -339,11 +339,16 @@ class TreeView implements ListViewDelegate {
   }
 
   String listViewDropEffect(ListView view, MouseEvent event) {
+    List<String> dragSelection = _innerDragSelection(event.dataTransfer);
     String nodeUID = null;
     if (_currentDragOverCell != null) {
       nodeUID = _currentDragOverCell.nodeUID;
     }
-    return _delegate.treeViewDropEffect(this, event.dataTransfer, nodeUID);
+    if (dragSelection != null) {
+      return _delegate.treeViewDropCellsEffect(this, dragSelection, nodeUID);
+    } else {
+      return _delegate.treeViewDropEffect(this, event.dataTransfer, nodeUID);
+    }
   }
 
   List<String> _innerDragSelection(DataTransfer dataTransfer) {

ide/app/lib/ui/widgets/treeview_delegate.dart

@@ -79,6 +79,17 @@ abstract class TreeViewDelegate {
   String treeViewDropEffect(TreeView view,
                             DataTransfer dataTransfer,
                             String nodeUID) => null;
+
+  /**
+   * This method is called when a selection of TreeView is dragged,
+   * on dragenter.
+   * Return 'copy', 'move', 'link' or 'none'.
+   * It will adjust the visual of the mouse cursor when the item is
+   * dragged over the treeview.
+   */
+  String treeViewDropCellsEffect(TreeView view,
+                                 List<String> nodesUIDs,
+                                 String nodeUID) => null;
 
   /**
    * This method is called when the dragged item is actually dropped on the

ide/app/lib/workspace.dart

@@ -730,7 +730,11 @@ class Folder extends Container {
     });
   }
 
-  Future<File> importFile(chrome.ChromeFileEntry sourceEntry) {
+  /**
+   * This method will import a file entry that might be from an other
+   * filesystem to the current folder.
+   */
+  Future<File> importFileEntry(chrome.ChromeFileEntry sourceEntry) {
     return createNewFile(sourceEntry.name).then((File file) {
       sourceEntry.readBytes().then((chrome.ArrayBuffer buffer) {
         return file.setBytes(buffer.getBytes());
@@ -739,15 +743,19 @@ class Folder extends Container {
     });
   }
 
-  Future importFolder(chrome.DirectoryEntry entry) {
+  /**
+   * This method will copy a directory entry that might be from an other
+   * filesystem to the current folder.
+   */
+  Future importDirectoryEntry(chrome.DirectoryEntry entry) {
     return createNewFolder(entry.name).then((Folder folder) {
       return entry.createReader().readEntries().then((List<chrome.Entry> entries) {
         List<Future> futures = [];
         for(chrome.Entry child in entries) {
           if (child is chrome.DirectoryEntry) {
-            futures.add(folder.importFolder(child));
+            futures.add(folder.importDirectoryEntry(child));
           } else if (child is chrome.ChromeFileEntry) {
-            futures.add(folder.importFile(child));
+            futures.add(folder.importFileEntry(child));
           }
         }
         return Future.wait(futures).then((_) {
@@ -756,6 +764,18 @@ class Folder extends Container {
       });
     });
   }
+
+  /**
+   * This method will copy a resource entry that might be from an other
+   * filesystem to the current folder.
+   */
+  Future importResource(Resource res) {
+    if (res.entry is chrome.ChromeFileEntry) {
+      return importFileEntry(res.entry);
+    } else if (res.entry is chrome.DirectoryEntry) {
+      return importDirectoryEntry(res.entry);
+    }
+  }
 
   Future delete() {
     return _dirEntry.removeRecursively().then((_) => _parent._removeChild(this));

ide/app/spark.dart

@@ -2498,8 +2498,7 @@ class GitAuthenticationDialog extends SparkActionWithDialog {
 }
 
 class ImportFileAction extends SparkAction implements ContextAction {
-  ImportFileAction(Spark spark) : super(spark, "file-import", "Import File…") {
-  }
+  ImportFileAction(Spark spark) : super(spark, "file-import", "Import File…");
 
   void _invoke([List<ws.Resource> resources]) {
     chrome.ChooseEntryOptions options = new chrome.ChooseEntryOptions(
@@ -2508,7 +2507,7 @@ class ImportFileAction extends SparkAction implements ContextAction {
       chrome.ChromeFileEntry entry = res.entry;
       if (entry != null) {
         ws.Folder folder = resources.first;
-        folder.importFile(entry).catchError((e) {
+        folder.importFileEntry(entry).catchError((e) {
           spark.showErrorMessage('Error while importing file', e);
         });
       }
@@ -2521,8 +2520,7 @@ class ImportFileAction extends SparkAction implements ContextAction {
 }
 
 class ImportFolderAction extends SparkAction implements ContextAction {
-  ImportFolderAction(Spark spark) : super(spark, "folder-import", "Import Folder…") {
-  }
+  ImportFolderAction(Spark spark) : super(spark, "folder-import", "Import Folder…");
 
   void _invoke([List<ws.Resource> resources]) {
     chrome.ChooseEntryOptions options = new chrome.ChooseEntryOptions(
@@ -2531,7 +2529,7 @@ class ImportFolderAction extends SparkAction implements ContextAction {
       chrome.DirectoryEntry entry = res.entry;
       if (entry != null) {
         ws.Folder folder = resources.first;
-        folder.importFolder(entry).catchError((e) {
+        folder.importDirectoryEntry(entry).catchError((e) {
           spark.showErrorMessage('Error while importing folder', e);
         });
       }