panel/plugin: Fix settings storing/restoring

- Add PlutingSettings::storeToCache() for the plugin configure dialog to
  be able to store to cache on closing the dialog -> after re-showing or
  showing freshly created one, we expect to be able to reset to the
  values shown initialy in this dialog.

- Delete plugin's config dialog before deleting the plugin object
  itself, as the config dialog can rely/use other plugin objects and
  deleting/closing the dialog late after plugin object destroyed can
  cause problems (invalid memory access).

panel/lxqtpanelpluginconfigdialog.cpp

@@ -58,6 +58,15 @@ PluginSettings& LXQtPanelPluginConfigDialog::settings() const
 }
 
 
+/************************************************
+
+ ************************************************/
+void LXQtPanelPluginConfigDialog::closeEvent(QCloseEvent *event)
+{
+    mSettings.storeToCache();
+    return QDialog::closeEvent(event);
+}
+
 
 /************************************************
 

panel/lxqtpanelpluginconfigdialog.h

@@ -35,6 +35,7 @@
 #include "pluginsettings.h"
 
 class QComboBox;
+class QCloseEvent;
 
 class LXQT_PANEL_API LXQtPanelPluginConfigDialog : public QDialog
 {
@@ -46,6 +47,9 @@ class LXQT_PANEL_API LXQtPanelPluginConfigDialog : public QDialog
 
     PluginSettings &settings() const;
 
+protected:
+    virtual void closeEvent(QCloseEvent *event) override;
+
 protected slots:
     /*
       Saves settings in conf file.

panel/plugin.cpp

@@ -188,6 +188,8 @@ Plugin::Plugin(const LXQt::PluginInfo &desktopFile, LXQt::Settings *settings, co
  ************************************************/
 Plugin::~Plugin()
 {
+    if (mConfigDialog)
+        delete mConfigDialog.data();
     delete mPlugin;
     delete mPluginLoader;
     delete mSettings;
@@ -515,7 +517,6 @@ void Plugin::showConfigureDialog()
     if (!mConfigDialog)
         return;
 
-    connect(this, &Plugin::destroyed, mConfigDialog.data(), &QWidget::close);
     mPanel->willShowWindow(mConfigDialog);
     mConfigDialog->show();
     mConfigDialog->raise();

panel/pluginsettings.cpp

@@ -209,6 +209,14 @@ void PluginSettings::loadFromCache()
     d->mSettings->endGroup();
 }
 
+void PluginSettings::storeToCache()
+{
+    Q_D(PluginSettings);
+    d->mSettings->beginGroup(d->mGroup);
+    d->mOldSettings.loadFromSettings();
+    d->mSettings->endGroup();
+}
+
 PluginSettings* PluginSettingsFactory::create(LXQt::Settings *settings, const QString &group, QObject *parent/* = nullptr*/)
 {
     return new PluginSettings{settings, group, parent};

panel/pluginsettings.h

@@ -81,6 +81,7 @@ class LXQT_PANEL_API PluginSettings : public QObject
     void endGroup();
 
     void loadFromCache();
+    void storeToCache();
 
 signals:
     void settingsChanged();