Apply timer spinbox workaround to QgsDoubleSpinBox too

To prevent double changed event fired in case the slot
takes too long to execute.

python/gui/auto_generated/editorwidgets/qgsdoublespinbox.sip.in

@@ -145,6 +145,8 @@ is equal to minimum(). Typical use is to indicate that this choice has a special
 
     virtual void wheelEvent( QWheelEvent *event );
 
+    virtual void timerEvent( QTimerEvent *event );
+
 
 };
 

src/gui/editorwidgets/qgsdoublespinbox.cpp

@@ -93,6 +93,17 @@ void QgsDoubleSpinBox::wheelEvent( QWheelEvent *event )
   setSingleStep( step );
 }
 
+void QgsDoubleSpinBox::timerEvent( QTimerEvent *event )
+{
+  // Process all events, which may include a mouse release event
+  // Only allow the timer to trigger additional value changes if the user
+  // has in fact held the mouse button, rather than the timer expiry
+  // simply appearing before the mouse release in the event queue
+  qApp->processEvents();
+  if ( QApplication::mouseButtons() & Qt::LeftButton )
+    QDoubleSpinBox::timerEvent( event );
+}
+
 void QgsDoubleSpinBox::paintEvent( QPaintEvent *event )
 {
   mLineEdit->setShowClearButton( shouldShowClearForValue( value() ) );

src/gui/editorwidgets/qgsdoublespinbox.h

@@ -146,6 +146,10 @@ class GUI_EXPORT QgsDoubleSpinBox : public QDoubleSpinBox
   protected:
     void changeEvent( QEvent *event ) override;
     void wheelEvent( QWheelEvent *event ) override;
+    // This is required because private implementation of
+    // QAbstractSpinBoxPrivate may trigger a second
+    // undesired event from the auto-repeat mouse timer
+    void timerEvent( QTimerEvent *event ) override;
 
   private slots:
     void changed( double value );