QmlDesigner: Allow drag-n-drop a bundle material to materials section

Fixes: QDS-8041
Change-Id: I848f636f41c58e11c719517f4073243a76e293b6
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>

share/qtcreator/qmldesigner/materialBrowserQmlSource/MaterialBrowser.qml

@@ -187,6 +187,21 @@ Item {
                     width: root.width
                     caption: qsTr("Materials")
                     hideHeader: !materialBrowserBundleModel.matBundleExists
+                    dropEnabled: true
+
+                    onDropEnter: (drag) => {
+                        drag.accepted = rootView.draggedBundleMaterial
+                        userMaterialsSection.highlight = rootView.draggedBundleMaterial
+                    }
+
+                    onDropExit: {
+                        userMaterialsSection.highlight = false
+                    }
+
+                    onDrop: {
+                        userMaterialsSection.highlight = false
+                        materialBrowserBundleModel.addToProject(rootView.draggedBundleMaterial)
+                    }
 
                     Grid {
                         id: grid

src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.cpp

@@ -139,14 +139,24 @@ bool MaterialBrowserWidget::eventFilter(QObject *obj, QEvent *event)
                 mimeData->setData(Constants::MIME_TYPE_BUNDLE_MATERIAL, data);
                 mimeData->removeFormat("text/plain");
 
+                if (!m_draggedBundleMaterial) {
+                    m_draggedBundleMaterial = m_bundleMaterialToDrag;
+                    emit draggedBundleMaterialChanged();
+                }
+
                 emit bundleMaterialDragStarted(m_bundleMaterialToDrag);
                 model->startDrag(mimeData, m_bundleMaterialToDrag->icon().toLocalFile());
-                m_bundleMaterialToDrag = {};
+                m_bundleMaterialToDrag = nullptr;
             }
         }
     } else if (event->type() == QMouseEvent::MouseButtonRelease) {
         m_materialToDrag = {};
-        m_bundleMaterialToDrag = {};
+        m_bundleMaterialToDrag = nullptr;
+
+        if (m_draggedBundleMaterial) {
+            m_draggedBundleMaterial = nullptr;
+            emit draggedBundleMaterialChanged();
+        }
     }
 
     return QObject::eventFilter(obj, event);

src/plugins/qmldesigner/components/materialbrowser/materialbrowserwidget.h

@@ -58,6 +58,7 @@ class PreviewImageProvider;
 class MaterialBrowserWidget : public QFrame
 {
     Q_OBJECT
+    Q_PROPERTY(BundleMaterial *draggedBundleMaterial MEMBER m_draggedBundleMaterial NOTIFY draggedBundleMaterialChanged)
 
 public:
     MaterialBrowserWidget(MaterialBrowserView *view);
@@ -81,6 +82,7 @@ public:
 
 signals:
     void bundleMaterialDragStarted(QmlDesigner::BundleMaterial *bundleMat);
+    void draggedBundleMaterialChanged();
 
 protected:
     bool eventFilter(QObject *obj, QEvent *event) override;
@@ -102,6 +104,7 @@ private:
 
     ModelNode m_materialToDrag;
     BundleMaterial *m_bundleMaterialToDrag = nullptr;
+    BundleMaterial *m_draggedBundleMaterial = nullptr;
     QPoint m_dragStartPoint;
 };