QmlDesigner: Clear material preview cache on detach

The previews are cached based on modelnode internal id, which can
overlap between documents, resulting in briefly showing incorrect
preview when new document is opened. Also, never clearing the cache
leads to leaking memory.

Fixed the issue by clearing the preview cache whenever all materials
are removed from browser (model detach and material library deletion).

Change-Id: Idad39fef62871c4e94f35604e643c7195ae9ec81
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

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

@@ -212,6 +212,7 @@ bool MaterialBrowserView::isTexture(const ModelNode &node) const
 void MaterialBrowserView::modelAboutToBeDetached(Model *model)
 {
     m_widget->materialBrowserModel()->setMaterials({}, m_hasQuick3DImport);
+    m_widget->clearPreviewCache();
 
     if (m_propertyGroupsLoaded) {
         m_propertyGroupsLoaded = false;
@@ -301,6 +302,7 @@ void MaterialBrowserView::nodeAboutToBeRemoved(const ModelNode &removedNode)
     // removing the material editor node
     if (removedNode.id() == Constants::MATERIAL_LIB_ID) {
         m_widget->materialBrowserModel()->setMaterials({}, m_hasQuick3DImport);
+        m_widget->clearPreviewCache();
         return;
     }
 

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

@@ -62,6 +62,11 @@ public:
         m_pixmaps.insert(node.internalId(), pixmap);
     }
 
+    void clearPixmapCache()
+    {
+        m_pixmaps.clear();
+    }
+
     QPixmap requestPixmap(const QString &id,
                           QSize *size,
                           [[maybe_unused]] const QSize &requestedSize) override
@@ -257,6 +262,11 @@ QQuickWidget *MaterialBrowserWidget::quickWidget() const
     return m_quickWidget.data();
 }
 
+void MaterialBrowserWidget::clearPreviewCache()
+{
+    m_previewImageProvider->clearPixmapCache();
+}
+
 QPointer<MaterialBrowserModel> MaterialBrowserWidget::materialBrowserModel() const
 {
     return m_materialBrowserModel;

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

@@ -54,6 +54,8 @@ public:
 
     QQuickWidget *quickWidget() const;
 
+    void clearPreviewCache();
+
 protected:
     bool eventFilter(QObject *obj, QEvent *event) override;