Don't run searches for a preview widget while it's hidden, and run one as soon as the sort page is shown

src/smartplaylists/querywizardplugin.cpp

@@ -57,11 +57,15 @@ public:
 
 class QueryWizardPlugin::SortPage : public QWizardPage {
 public:
-  SortPage(QWidget* parent, int next_id)
+  SortPage(QueryWizardPlugin* plugin, QWidget* parent, int next_id)
-    : QWizardPage(parent), next_id_(next_id) {}
+    : QWizardPage(parent), next_id_(next_id), plugin_(plugin) {}
+
+  void showEvent(QShowEvent*) { plugin_->UpdateSortPreview(); }
 
   int nextId() const { return next_id_; }
   int next_id_;
+
+  QueryWizardPlugin* plugin_;
 };
 
 
@@ -86,7 +90,7 @@ int QueryWizardPlugin::CreatePages(QWizard* wizard, int finish_page_id) {
   // Create the UI
   search_page_ = new SearchPage(wizard);
 
-  QWizardPage* sort_page = new SortPage(wizard, finish_page_id);
+  QWizardPage* sort_page = new SortPage(this, wizard, finish_page_id);
   sort_ui_.reset(new Ui_SmartPlaylistQuerySortPage);
   sort_ui_->setupUi(sort_page);
 

src/smartplaylists/searchpreview.cpp

@@ -63,8 +63,8 @@ void SearchPreview::Update(const Search& search) {
     return;
   }
 
-  if (generator_) {
+  if (generator_ || isHidden()) {
-    // It's busy generating something already
+    // It's busy generating something already, or the widget isn't visible
     pending_search_ = search;
     return;
   }
@@ -72,6 +72,16 @@ void SearchPreview::Update(const Search& search) {
   RunSearch(search);
 }
 
+void SearchPreview::showEvent(QShowEvent* e) {
+  if (pending_search_.is_valid() && !generator_) {
+    // There was a search waiting while we were hidden, so run it now
+    RunSearch(pending_search_);
+    pending_search_ = Search();
+  }
+
+  QWidget::showEvent(e);
+}
+
 void SearchPreview::RunSearch(const Search& search) {
   generator_.reset(new QueryGenerator);
   generator_->set_library(backend_);

src/smartplaylists/searchpreview.h

@@ -42,6 +42,9 @@ public:
 
   void Update(const Search& search);
 
+protected:
+  void showEvent(QShowEvent*);
+
 private:
   void RunSearch(const Search& search);