fix #118,support dragging a file at windows group

plasmoid/contents/ui/MouseHandler.qml

@@ -178,6 +178,7 @@ Item {
                 }
 
                 if (parent.hoveredItem.m.IsGroupParent === true) {
+                    root.showPreviewForTasks(parent.hoveredItem);
                    // groupDialog.visualParent = parent.hoveredItem;
                    // groupDialog.visible = true;
                 } else if (parent.hoveredItem.m.IsLauncher !== true) {

plasmoid/contents/ui/TaskDelegate.qml

@@ -857,8 +857,6 @@ MouseArea{
     }
     ///window previews////
 
-
-
     function modelIndex(){
         return tasksModel.makeModelIndex(index);
     }
@@ -867,6 +865,13 @@ MouseArea{
         inBlockingAnimation = value;
     }
 
+    function slotShowPreviewForTasks(group) {
+        if (group === mainItemContainer) {
+            preparePreviewWindow();
+            windowsPreviewDlg.show();
+        }
+    }
+
     function slotPublishGeometries() {
         if ((isWindow || isStartup || isGroupParent) && tasksModel) {
             tasksModel.requestPublishDelegateGeometry(mainItemContainer.modelIndex(),
@@ -890,6 +895,7 @@ MouseArea{
         root.draggingFinished.connect(handlerDraggingFinished);
         root.clearZoomSignal.connect(clearZoom);
         root.publishTasksGeometries.connect(slotPublishGeometries);
+        root.showPreviewForTasks.connect(slotShowPreviewForTasks);
 
         //fix wrong positioning of launchers....
         for(var i=0; i<tasksModel.launcherList.length; ++i){

plasmoid/contents/ui/ToolTipDelegate2.qml

@@ -25,6 +25,8 @@ import QtQuick.Layouts 1.1
 import QtGraphicalEffects 1.0
 import QtQml.Models 2.2
 
+import org.kde.draganddrop 2.0
+
 import org.kde.plasma.core 2.0 as PlasmaCore
 import org.kde.plasma.components 2.0 as PlasmaComponents
 import org.kde.plasma.extras 2.0 as PlasmaExtras
@@ -107,6 +109,31 @@ PlasmaExtras.ScrollArea {
             return singleTask.containsMouse() || groupTask.containsMouse();
         }
 
+        DropArea {
+            id: dropMainArea
+            anchors.fill: contentItem
+            enabled: isGroup
+
+            preventStealing: true
+
+            property bool dragInside: false
+
+            property QtObject currentWindow
+
+            onDragLeave: {
+                windowsPreviewDlg.hide();
+            }
+
+            onDragMove: {
+                var current = groupTask.childAtPos(event.x, event.y);
+
+                if (current && currentWindow !== current && current.submodelIndex) {
+                    currentWindow = current;
+                    tasksModel.requestActivate(current.submodelIndex);
+                }
+            }
+        }
+
         ToolTipInstance {
             id: singleTask
             visible: !isGroup
@@ -138,6 +165,28 @@ PlasmaExtras.ScrollArea {
 
                 return false;
             }
+
+            function childAtPos(x, y){
+                var tasks = groupTask.children;
+
+                for(var i=0; i<tasks.length; ++i){
+                    var task = tasks[i];
+
+                    var choords = contentItem.mapFromItem(task,0, 0);
+
+                    if(choords.y < 0)
+                        choords.y = 0;
+                    if(choords.x < 0)
+                        choords.x = 0;
+
+                    if( (x>=choords.x) && (x<=choords.x+task.width)
+                            && (y>=choords.y) && (y<=choords.y+task.height)){
+                        return task;
+                    }
+                }
+
+                return null;
+            }
         }
     }
 }

plasmoid/contents/ui/ToolTipInstance.qml

@@ -30,6 +30,8 @@ import org.kde.plasma.components 2.0 as PlasmaComponents
 import org.kde.plasma.extras 2.0 as PlasmaExtras
 import org.kde.kquickcontrolsaddons 2.0 as KQuickControlsAddons
 
+import org.kde.draganddrop 2.0
+
 import org.kde.taskmanager 0.1 as TaskManager
 
 Column {

plasmoid/contents/ui/main.qml

@@ -134,6 +134,7 @@ Item {
     signal signalAnimationsNeedLength(int value);
     signal signalAnimationsNeedThickness(int value);
     signal signalDraggingState(bool value);
+    signal showPreviewForTasks(QtObject group);
     //trigger updating scaling of neighbour delegates of zoomed delegate
     signal updateScale(int delegateIndex, real newScale, real step)
     signal publishTasksGeometries();