[FEATURE] Layer tree indicators for memory layers

Shows a memory layer icon in the layer tree for all memory layers, with a tooltip warning that the contents of the layer will be lost when closing the project. Should help avoid data loss by users who don't realise that certain layers are temporary only.
qgis · Aug 6, 2018 · a953587 · a953587
1 parent f3235f7
commit a953587
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diff --git a/src/app/CMakeLists.txt b/src/app/CMakeLists.txt
@@ -56,6 +56,7 @@ SET(QGIS_APP_SRCS
   qgslabelingwidget.cpp
   qgslayertreeviewembeddedindicator.cpp
   qgslayertreeviewfilterindicator.cpp
+  qgslayertreeviewmemoryindicator.cpp
   qgsloadstylefromdbdialog.cpp
   qgsmapcanvasdockwidget.cpp
   qgsmaplayerstyleguiutils.cpp
@@ -275,6 +276,7 @@ SET (QGIS_APP_MOC_HDRS
   qgslabelingwidget.h
   qgslabelpropertydialog.h
   qgslayertreeviewembeddedindicator.h
+  qgslayertreeviewmemoryindicator.h
   qgslayertreeviewfilterindicator.h
   qgsloadstylefromdbdialog.h
   qgsmapcanvasdockwidget.h

diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
@@ -206,6 +206,7 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 #include "qgslayertreeviewdefaultactions.h"
 #include "qgslayertreeviewembeddedindicator.h"
 #include "qgslayertreeviewfilterindicator.h"
+#include "qgslayertreeviewmemoryindicator.h"
 #include "qgslayout.h"
 #include "qgslayoutatlas.h"
 #include "qgslayoutcustomdrophandler.h"
@@ -3803,6 +3804,7 @@ void QgisApp::initLayerTreeView()
   mLayerTreeView->setMenuProvider( new QgsAppLayerTreeViewMenuProvider( mLayerTreeView, mMapCanvas ) );
   new QgsLayerTreeViewFilterIndicatorProvider( mLayerTreeView );  // gets parented to the layer view
   new QgsLayerTreeViewEmbeddedIndicatorProvider( mLayerTreeView );  // gets parented to the layer view
+  new QgsLayerTreeViewMemoryIndicatorProvider( mLayerTreeView );  // gets parented to the layer view
 
   setupLayerTreeViewFromSettings();
 

diff --git a/src/app/qgslayertreeviewmemoryindicator.cpp b/src/app/qgslayertreeviewmemoryindicator.cpp
@@ -0,0 +1,95 @@
+/***************************************************************************
+  qgslayertreeviewmemoryindicator.h
+  --------------------------------------
+  Date                 : July 2018
+  Copyright            : (C) 2018 by 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 "qgslayertreeviewmemoryindicator.h"
+#include "qgslayertree.h"
+#include "qgslayertreemodel.h"
+#include "qgslayertreeview.h"
+
+QgsLayerTreeViewMemoryIndicatorProvider::QgsLayerTreeViewMemoryIndicatorProvider( QgsLayerTreeView *view )
+  : QObject( view )
+  , mLayerTreeView( view )
+{
+  mIcon = QgsApplication::getThemeIcon( QStringLiteral( "/mActionCreateMemory.svg" ) );
+
+  QgsLayerTree *tree = mLayerTreeView->layerTreeModel()->rootGroup();
+  onAddedChildren( tree, 0, tree->children().count() - 1 );
+
+  connect( tree, &QgsLayerTree::addedChildren, this, &QgsLayerTreeViewMemoryIndicatorProvider::onAddedChildren );
+}
+
+void QgsLayerTreeViewMemoryIndicatorProvider::onAddedChildren( QgsLayerTreeNode *node, int indexFrom, int indexTo )
+{
+  // recursively populate indicators
+  QList<QgsLayerTreeNode *> children = node->children();
+  for ( int i = indexFrom; i <= indexTo; ++i )
+  {
+    QgsLayerTreeNode *childNode = children[i];
+
+    if ( QgsLayerTree::isGroup( childNode ) )
+    {
+      onAddedChildren( childNode, 0, childNode->children().count() - 1 );
+    }
+    else if ( QgsLayerTree::isLayer( childNode ) )
+    {
+      if ( QgsLayerTreeLayer *layerNode = dynamic_cast< QgsLayerTreeLayer * >( childNode ) )
+      {
+        if ( layerNode->layer() && layerNode->layer()->dataProvider()->name() == QLatin1String( "memory" ) )
+          addIndicatorForMemoryLayer( childNode );
+        else if ( !layerNode->layer() )
+        {
+          // wait for layer to be loaded (e.g. when loading project, first the tree is loaded, afterwards the references to layers are resolved)
+          connect( layerNode, &QgsLayerTreeLayer::layerLoaded, this, &QgsLayerTreeViewMemoryIndicatorProvider::onLayerLoaded );
+        }
+      }
+    }
+  }
+}
+
+void QgsLayerTreeViewMemoryIndicatorProvider::onLayerLoaded()
+{
+  QgsLayerTreeLayer *layerNode = qobject_cast<QgsLayerTreeLayer *>( sender() );
+  if ( !layerNode )
+    return;
+
+  if ( layerNode->layer() && layerNode->layer()->dataProvider()->name() == QLatin1String( "memory" ) )
+    addIndicatorForMemoryLayer( layerNode );
+}
+
+std::unique_ptr< QgsLayerTreeViewIndicator > QgsLayerTreeViewMemoryIndicatorProvider::newIndicator()
+{
+  std::unique_ptr< QgsLayerTreeViewIndicator > indicator = qgis::make_unique< QgsLayerTreeViewIndicator >( this );
+  indicator->setIcon( mIcon );
+  indicator->setToolTip( tr( "Temporary scratch layer only<br><b>Contents will be discarded after closing this project</b>" ) );
+  mIndicators.insert( indicator.get() );
+  return indicator;
+}
+
+void QgsLayerTreeViewMemoryIndicatorProvider::addIndicatorForMemoryLayer( QgsLayerTreeNode *node )
+{
+  const QList<QgsLayerTreeViewIndicator *> nodeIndicators = mLayerTreeView->indicators( node );
+
+  // maybe the indicator exists already
+  for ( QgsLayerTreeViewIndicator *indicator : nodeIndicators )
+  {
+    if ( mIndicators.contains( indicator ) )
+    {
+      return;
+    }
+  }
+
+  // it does not exist: need to create a new one
+  mLayerTreeView->addIndicator( node, newIndicator().release() );
+}
diff --git a/src/app/qgslayertreeviewmemoryindicator.h b/src/app/qgslayertreeviewmemoryindicator.h
@@ -0,0 +1,49 @@
+/***************************************************************************
+  qgslayertreeviewmemoryindicator.h
+  --------------------------------------
+  Date                 : July 2018
+  Copyright            : (C) 2018 by 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSLAYERTREEVIEWMEMORYINDICATOR_H
+#define QGSLAYERTREEVIEWMEMORYINDICATOR_H
+
+#include "qgslayertreeviewindicator.h"
+
+#include <QSet>
+#include <memory>
+
+class QgsLayerTreeNode;
+class QgsLayerTreeView;
+
+//! Adds indicators showing whether layers are memory layers.
+class QgsLayerTreeViewMemoryIndicatorProvider : public QObject
+{
+    Q_OBJECT
+  public:
+    explicit QgsLayerTreeViewMemoryIndicatorProvider( QgsLayerTreeView *view );
+
+  private slots:
+    //! Connects to signals of layers newly added to the tree
+    void onAddedChildren( QgsLayerTreeNode *node, int indexFrom, int indexTo );
+    void onLayerLoaded();
+
+  private:
+    std::unique_ptr< QgsLayerTreeViewIndicator > newIndicator();
+    void addIndicatorForMemoryLayer( QgsLayerTreeNode *node );
+
+  private:
+    QgsLayerTreeView *mLayerTreeView = nullptr;
+    QIcon mIcon;
+    QSet<QgsLayerTreeViewIndicator *> mIndicators;
+};
+
+#endif // QGSLAYERTREEVIEWMEMORYINDICATOR_H