Add layout validity check for map crs

src/app/CMakeLists.txt

@@ -204,6 +204,7 @@ SET(QGIS_APP_SRCS
   layout/qgslayoutscalebarwidget.cpp
   layout/qgslayoutshapewidget.cpp
   layout/qgslayouttablebackgroundcolorsdialog.cpp
+  layout/qgslayoutvaliditychecks.cpp
   layout/qgsreportfieldgroupsectionwidget.cpp
   layout/qgsreportlayoutsectionwidget.cpp
   layout/qgsreportorganizerwidget.cpp
@@ -433,6 +434,7 @@ SET (QGIS_APP_MOC_HDRS
   layout/qgslayoutscalebarwidget.h
   layout/qgslayoutshapewidget.h
   layout/qgslayouttablebackgroundcolorsdialog.h
+  layout/qgslayoutvaliditychecks.h
   layout/qgsreportfieldgroupsectionwidget.h
   layout/qgsreportlayoutsectionwidget.h
   layout/qgsreportorganizerwidget.h

src/app/layout/qgslayoutvaliditychecks.cpp

@@ -0,0 +1,44 @@
+/***************************************************************************
+                              qgslayoutvaliditychecks.cpp
+                              ---------------------------
+    begin                : November 2018
+    copyright            : (C) 2018 Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgslayoutvaliditychecks.h"
+#include "qgsvaliditycheckcontext.h"
+#include "qgslayoutitemmap.h"
+#include "qgslayout.h"
+
+QList<QgsValidityCheckResult> QgsLayoutMapCrsValidityCheck::runCheck( const QgsValidityCheckContext *context, QgsFeedback * ) const
+{
+  QList<QgsValidityCheckResult> results;
+  const QgsLayoutValidityCheckContext *layoutContext = dynamic_cast< const QgsLayoutValidityCheckContext * >( context );
+  if ( !layoutContext )
+    return results;
+
+  QList< QgsLayoutItemMap * > mapItems;
+  layoutContext->layout->layoutItems( mapItems );
+  for ( QgsLayoutItemMap *map : qgis::as_const( mapItems ) )
+  {
+    if ( map->crs().authid() == QStringLiteral( "EPSG:3857" ) )
+    {
+      QgsValidityCheckResult res;
+      res.type = QgsValidityCheckResult::Warning;
+      res.title = tr( "Map projection is misleading" );
+      res.detailedDescription = tr( "The projection for the map item %1 is set to <i>Web Mercator (EPSG:3857)</i> which misrepresents areas and shapes. Consider using an appropriate local projection instead." ).arg( map->displayName() );
+      results.append( res );
+    }
+  }
+
+  return results;
+}

src/app/layout/qgslayoutvaliditychecks.h

@@ -0,0 +1,33 @@
+/***************************************************************************
+                              qgslayoutvaliditychecks.h
+                              ---------------------------
+    begin                : November 2018
+    copyright            : (C) 2018 Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsabstractvaliditycheck.h"
+
+class QgsLayoutMapCrsValidityCheck : public QgsAbstractValidityCheck
+{
+    Q_OBJECT
+
+  public:
+
+    QString id() const override { return "map_crs_check"; }
+    int checkType() const override { return QgsAbstractValidityCheck::TypeLayoutCheck; }
+    QString name() const override { return "Map CRS Check"; }
+    QList< QgsValidityCheckResult > runCheck( const QgsValidityCheckContext *context, QgsFeedback *feedback ) const override;
+
+
+
+
+};

src/app/qgisapp.cpp

@@ -328,6 +328,7 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 #include "qgsgui.h"
 #include "qgsdatasourcemanagerdialog.h"
 #include "qgsappwindowmanager.h"
+#include "qgsvaliditycheckregistry.h"
 
 #include "qgsuserprofilemanager.h"
 #include "qgsuserprofile.h"
@@ -422,6 +423,7 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 #include "qgsgeometryvalidationmodel.h"
 #include "qgsgeometryvalidationdock.h"
 #include "qgsmaptooltrimextendfeature.h"
+#include "qgslayoutvaliditychecks.h"
 
 #include "vertextool/qgsvertextool.h"
 
@@ -1231,6 +1233,8 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, bool skipVersionCh
     setIconSizes( size );
   }
 
+  QgsApplication::validityCheckRegistry()->addCheck( new QgsLayoutMapCrsValidityCheck() );
+
   mSplash->showMessage( tr( "Initializing file filters" ), Qt::AlignHCenter | Qt::AlignBottom );
   qApp->processEvents();