dynamic clearbutton in the filter bar

mention in #27

Author: luebking

Phototonic.cpp

@@ -1082,6 +1082,8 @@ void Phototonic::createToolBars() {
                                 rtfm, filterLineEdit);
         }
     });
+    filterLineEdit->setMouseTracking(true);
+    filterLineEdit->installEventFilter(this);
 
     myMainToolBar->addSeparator();
     myMainToolBar->addWidget(filterLineEdit);
@@ -3462,6 +3464,15 @@ bool Phototonic::eventFilter(QObject *o, QEvent *e)
         return QMainWindow::eventFilter(o, e);
     }
 
+    if (o == filterLineEdit) {
+        if (e->type() == QEvent::Enter) {
+            filterLineEdit->setClearButtonEnabled(!filterLineEdit->text().isEmpty());
+        } else if (e->type() == QEvent::Leave) {
+            filterLineEdit->setClearButtonEnabled(false);
+        }
+        return QMainWindow::eventFilter(o, e);
+    }
+
     static QPropertyAnimation *animator = nullptr;
     auto scrollThumbs = [=](int steps) {
         if (!animator) {