Indicate keyboard focus for Advanced toggle button on Windows

For details see comments in code.

GnuPG-bug-id: 6149

src/dialogs/certifywidget.cpp

@@ -79,7 +79,15 @@ private:
 AnimatedExpander::AnimatedExpander(const QString &title, const QString &accessibleTitle, QWidget *parent)
     : QWidget{parent}
 {
+#ifdef Q_OS_WIN
+    // draw dotted focus frame if button has focus; otherwise, draw invisible frame using background color
+    toggleButton.setStyleSheet(QStringLiteral("QToolButton { border: 1px solid palette(window); }"
+                                              "QToolButton:focus { border: 1px dotted palette(window-text); }"));
+#else
+    // this works with Breeze style because Breeze draws the focus frame when drawing CE_ToolButtonLabel
+    // while the Windows styles (and Qt's common base style) draw the focus frame before drawing CE_ToolButtonLabel
     toggleButton.setStyleSheet(QStringLiteral("QToolButton { border: none; }"));
+#endif
     toggleButton.setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
     toggleButton.setArrowType(Qt::ArrowType::RightArrow);
     toggleButton.setText(title);