[date widget] fix current date can't be picked

fix #16579

src/gui/editorwidgets/qgsdatetimeedit.cpp

@@ -13,12 +13,14 @@
  *                                                                         *
  ***************************************************************************/
 
+#include <QCalendarWidget>
 #include <QLineEdit>
 #include <QMouseEvent>
 #include <QSettings>
 #include <QStyle>
 #include <QToolButton>
 
+
 #include "qgsdatetimeedit.h"
 
 #include "qgsapplication.h"
@@ -47,8 +49,16 @@ QgsDateTimeEdit::QgsDateTimeEdit( QWidget *parent )
 
   connect( this, &QDateTimeEdit::dateTimeChanged, this, &QgsDateTimeEdit::changed );
 
+  // set this by defaut to properly connect the calendar widget
+  setCalendarPopup( true );
+  // when clearing the widget, date of the QDateTimeEdit will be set to minimum date
+  // hence when the calendar popups, on selection changed if it set to the minimum date,
+  // the page of the current date will be shown
+  connect( calendarWidget(), &QCalendarWidget::selectionChanged, this, &QgsDateTimeEdit::calendarSelectionChanged );
+
   // init with current time so mIsNull is properly initialized
   QDateTimeEdit::setDateTime( QDateTime::currentDateTime() );
+
   setMinimumEditDateTime();
 }
 
@@ -64,6 +74,12 @@ void QgsDateTimeEdit::setAllowNull( bool allowNull )
 
 void QgsDateTimeEdit::clear()
 {
+  if ( calendarPopup() )
+  {
+    QDateTimeEdit::blockSignals( true );
+    QDateTimeEdit::setDateTime( minimumDateTime() );
+    QDateTimeEdit::blockSignals( false );
+  }
   changed( QDateTime() );
   emit dateTimeChanged( QDateTime() );
 }
@@ -73,6 +89,7 @@ void QgsDateTimeEdit::setEmpty()
   mNullLabel->setVisible( false );
   lineEdit()->setVisible( false );
   mClearButton->setVisible( mAllowNull );
+  mIsEmpty = true;
 }
 
 void QgsDateTimeEdit::mousePressEvent( QMouseEvent *event )
@@ -81,6 +98,7 @@ void QgsDateTimeEdit::mousePressEvent( QMouseEvent *event )
   if ( mAllowNull && mIsNull && lerect.contains( event->pos() ) )
     return;
 
+
   QDateTimeEdit::mousePressEvent( event );
 }
 
@@ -93,6 +111,14 @@ void QgsDateTimeEdit::changed( const QDateTime &dateTime )
   lineEdit()->setVisible( !mAllowNull || !mIsNull );
 }
 
+void QgsDateTimeEdit::calendarSelectionChanged()
+{
+  if ( mAllowNull && calendarWidget() && calendarWidget()->selectedDate() == minimumDate() )
+  {
+    calendarWidget()->setCurrentPage( QDate::currentDate().year(), QDate::currentDate().month() );
+  }
+}
+
 int QgsDateTimeEdit::spinButtonWidth() const
 {
   return calendarPopup() ? 25 : 18;

src/gui/editorwidgets/qgsdatetimeedit.h

@@ -74,6 +74,8 @@ class GUI_EXPORT QgsDateTimeEdit : public QDateTimeEdit
   private slots:
     void changed( const QDateTime &dateTime );
 
+    void calendarSelectionChanged();
+
 
   private:
     int spinButtonWidth() const;
@@ -101,7 +103,6 @@ class GUI_EXPORT QgsDateTimeEdit : public QDateTimeEdit
     {
       setMinimumDateTime( QDateTime::fromString( QStringLiteral( "0100-01-01" ), Qt::ISODate ) );
     }
-
 };
 
 #endif // QGSDATETIMEEDIT_H

src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp

@@ -67,7 +67,10 @@ void QgsDateTimeEditWrapper::initWidget( QWidget *editor )
   mQDateTimeEdit->setDisplayFormat( displayFormat );
 
   const bool calendar = config( QStringLiteral( "calendar_popup" ), true ).toBool();
-  mQDateTimeEdit->setCalendarPopup( calendar );
+  if ( calendar != mQDateTimeEdit->calendarPopup() )
+  {
+    mQDateTimeEdit->setCalendarPopup( calendar );
+  }
   if ( calendar && mQDateTimeEdit->calendarWidget() )
   {
     // highlight today's date