From 429ffde9670f997004eab8a7a05afedcb1abe648 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Wed, 7 Oct 2020 16:02:12 +1000
Subject: [PATCH] [gps] Ensure that the status bar GPS distance readout only
 shows in response to a mouse action and doesn't always re-show as a result of
 a GPS position change

Otherwise as soon as the message appears, it will endlessly
re-show as the GPS position is constantly changing. Instead
ensure that the message starts showing for a maximum of
2 seconds in response to a mouse movement, yet will update
during these 2 seconds if the GPS position is updated during
this time.
---
 src/app/gps/qgsgpsinformationwidget.cpp | 25 +++++++++++++++++++------
 src/app/gps/qgsgpsinformationwidget.h   |  3 ++-
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/app/gps/qgsgpsinformationwidget.cpp b/src/app/gps/qgsgpsinformationwidget.cpp
index 30ee14d9df62..266adb5d50f7 100644
--- a/src/app/gps/qgsgpsinformationwidget.cpp
+++ b/src/app/gps/qgsgpsinformationwidget.cpp
@@ -107,7 +107,7 @@ QgsGpsInformationWidget::QgsGpsInformationWidget( QgsMapCanvas *mapCanvas, QWidg
   connect( QgsProject::instance()->displaySettings(), &QgsProjectDisplaySettings::bearingFormatChanged, this, [ = ]
   {
     mBearingNumericFormat.reset( QgsProject::instance()->displaySettings()->bearingFormat()->clone() );
-    updateGpsDistanceStatusMessage();
+    updateGpsDistanceStatusMessage( false );
   } );
 
   mCanvasToWgs84Transform = QgsCoordinateTransform( mMapCanvas->mapSettings().destinationCrs(), mWgs84CRS, QgsProject::instance() );
@@ -1005,7 +1005,7 @@ void QgsGpsInformationWidget::displayGPSInformation( const QgsGpsInformation &in
       addVertex();
     }
 
-    updateGpsDistanceStatusMessage();
+    updateGpsDistanceStatusMessage( false );
   }
 
   if ( !std::isnan( info.direction ) || ( mTravelBearingCheckBox->isChecked() && !mSecondLastGpsPosition.isEmpty() ) )
@@ -1621,7 +1621,7 @@ void QgsGpsInformationWidget::cursorCoordinateChanged( const QgsPointXY &point )
   try
   {
     mLastCursorPosWgs84 = mCanvasToWgs84Transform.transform( point );
-    updateGpsDistanceStatusMessage();
+    updateGpsDistanceStatusMessage( true );
   }
   catch ( QgsCsException & )
   {
@@ -1629,11 +1629,24 @@ void QgsGpsInformationWidget::cursorCoordinateChanged( const QgsPointXY &point )
   }
 }
 
-void QgsGpsInformationWidget::updateGpsDistanceStatusMessage()
+void QgsGpsInformationWidget::updateGpsDistanceStatusMessage( bool forceDisplay )
 {
   if ( !mNmea )
     return;
 
+  if ( !forceDisplay )
+  {
+    // if we aren't forcing the display of the message (i.e. in direct response to a mouse cursor movement),
+    // then only show an updated message when the GPS position changes if the previous forced message occurred < 2 seconds ago.
+    // otherwise we end up showing infinite messages as the GPS position constantly changes...
+    if ( mLastForcedStatusUpdate.hasExpired( 2000 ) )
+      return;
+  }
+  else
+  {
+    mLastForcedStatusUpdate.restart();
+  }
+
   const double distance = mDistanceCalculator.convertLengthMeasurement( mDistanceCalculator.measureLine( QVector< QgsPointXY >() << mLastCursorPosWgs84 << mLastGpsPosition ),
                           QgsProject::instance()->distanceUnits() );
   const double bearing = 180 * mDistanceCalculator.bearing( mLastGpsPosition, mLastCursorPosWgs84 ) / M_PI;
@@ -1641,7 +1654,7 @@ void QgsGpsInformationWidget::updateGpsDistanceStatusMessage()
   const QString distanceString = QgsDistanceArea::formatDistance( distance, distanceDecimalPlaces, QgsProject::instance()->distanceUnits() );
   const QString bearingString = mBearingNumericFormat->formatDouble( bearing, QgsNumericFormatContext() );
 
-  QgisApp::instance()->statusBarIface()->showMessage( tr( "%1 (%2) from GPS location" ).arg( distanceString, bearingString ), 2000 );
+  QgisApp::instance()->statusBarIface()->showMessage( tr( "%1 (%2) from GPS location" ).arg( distanceString, bearingString ), forceDisplay ? 2000 : 2000 - mLastForcedStatusUpdate.elapsed() );
 }
 
 void QgsGpsInformationWidget::updateTimestampDestinationFields( QgsMapLayer *mapLayer )
@@ -1686,7 +1699,7 @@ void QgsGpsInformationWidget::tapAndHold( const QgsPointXY &mapPoint, QTapAndHol
   try
   {
     mLastCursorPosWgs84 = mCanvasToWgs84Transform.transform( mapPoint );
-    updateGpsDistanceStatusMessage();
+    updateGpsDistanceStatusMessage( true );
   }
   catch ( QgsCsException & )
   {
diff --git a/src/app/gps/qgsgpsinformationwidget.h b/src/app/gps/qgsgpsinformationwidget.h
index ec53fd18fb48..cdb5bc9e4128 100644
--- a/src/app/gps/qgsgpsinformationwidget.h
+++ b/src/app/gps/qgsgpsinformationwidget.h
@@ -136,7 +136,7 @@ class APP_EXPORT QgsGpsInformationWidget: public QgsPanelWidget, public QgsMapCa
 #endif
     void createRubberBand();
 
-    void updateGpsDistanceStatusMessage();
+    void updateGpsDistanceStatusMessage( bool forceDisplay );
 
     QgsCoordinateReferenceSystem mWgs84CRS;
     QgsCoordinateTransform mCanvasToWgs84Transform;
@@ -170,6 +170,7 @@ class APP_EXPORT QgsGpsInformationWidget: public QgsPanelWidget, public QgsMapCa
     std::unique_ptr< QgsBearingNumericFormat > mBearingNumericFormat;
 
     QElapsedTimer mLastRotateTimer;
+    QElapsedTimer mLastForcedStatusUpdate;
 
     friend class TestQgsGpsInformationWidget;
 };