Add keyboard shortcut for focusing search fields

Fixes #779

src/widgets/qsearchfield.h

@@ -22,6 +22,10 @@ class QSearchField : public QWidget {
 
   QString text() const;
   QString placeholderText() const;
+
+#ifndef Q_OS_MACOS
+  bool hasFocus() const;
+#endif
   void setFocus(Qt::FocusReason);
 
  public slots:

src/widgets/qsearchfield_nonmac.cpp

@@ -131,6 +131,11 @@ QString QSearchField::placeholderText() const {
   return pimpl->lineedit_->placeholderText();
 }
 
+bool QSearchField::hasFocus() const {
+  Q_ASSERT(pimpl && pimpl->lineedit_);
+  return pimpl && pimpl->lineedit_ && pimpl->lineedit_->hasFocus();
+}
+
 void QSearchField::setFocus(Qt::FocusReason reason) {
   Q_ASSERT(pimpl && pimpl->lineedit_);
   if (pimpl && pimpl->lineedit_) pimpl->lineedit_->setFocus(reason);