[FEATURE][browser] Restore preview functionality from old 2.x standalone

browser into inbuilt browser dock panel layer properties widget

src/app/qgisapp.cpp

@@ -1559,6 +1559,13 @@ QgisApp::~QgisApp()
     delete canvas;
   }
 
+  // these may have references to map layers which need to be cleaned up
+  delete mBrowserWidget;
+  mBrowserWidget = nullptr;
+  delete mBrowserWidget2;
+  mBrowserWidget2 = nullptr;
+  delete mBrowserModel;
+
   QgsGui::instance()->nativePlatformInterface()->cleanup();
 
   // This function *MUST* be the last one called, as it destroys in

src/gui/qgsbrowserdockwidget_p.cpp

@@ -40,6 +40,7 @@
 #include "qgsmeshlayer.h"
 #include "qgsgui.h"
 #include "qgsnative.h"
+#include "qgsmaptoolpan.h"
 #include <QDesktopServices>
 
 #include <QDragEnterEvent>
@@ -119,6 +120,19 @@ QgsBrowserLayerProperties::QgsBrowserLayerProperties( QWidget *parent )
   // we don't want links to open in the little widget, open them externally instead
   mMetadataTextBrowser->setOpenLinks( false );
   connect( mMetadataTextBrowser, &QTextBrowser::anchorClicked, this, &QgsBrowserLayerProperties::urlClicked );
+
+  mMapCanvas->setLayers( QList< QgsMapLayer * >() );
+  mMapCanvas->setMapTool( new QgsMapToolPan( mMapCanvas ) );
+  mMapCanvas->freeze( true );
+
+  connect( mTabWidget, &QTabWidget::currentChanged, this, [ = ]
+  {
+    if ( mTabWidget->currentWidget() == mPreviewTab && mMapCanvas->isFrozen() )
+    {
+      mMapCanvas->freeze( false );
+      mMapCanvas->refresh();
+    }
+  } );
 }
 
 class ProjectionSettingRestorer
@@ -159,6 +173,8 @@ void QgsBrowserLayerProperties::setItem( QgsDataItem *item )
   ProjectionSettingRestorer restorer;
   ( void )restorer; // no warnings
 
+  mLayer.reset();
+
   // find root item
   // we need to create a temporary layer to get metadata
   // we could use a provider but the metadata is not as complete and "pretty"  and this is easier
@@ -167,47 +183,17 @@ void QgsBrowserLayerProperties::setItem( QgsDataItem *item )
   {
     QgsDebugMsg( QStringLiteral( "creating raster layer" ) );
     // should copy code from addLayer() to split uri ?
-    std::unique_ptr<QgsRasterLayer> layer( new QgsRasterLayer( layerItem->uri(), layerItem->uri(), layerItem->providerKey() ) );
+    mLayer = qgis::make_unique< QgsRasterLayer >( layerItem->uri(), layerItem->uri(), layerItem->providerKey() );
-    if ( layer )
-    {
-      if ( layer->isValid() )
-      {
-        bool ok = false;
-        layer->loadDefaultMetadata( ok );
-        layerCrs = layer->crs();
-        layerMetadata = layer->htmlMetadata();
-      }
-    }
   }
   else if ( type == QgsMapLayer::MeshLayer )
   {
     QgsDebugMsg( QStringLiteral( "creating mesh layer" ) );
-    std::unique_ptr<QgsMeshLayer> layer( new QgsMeshLayer( layerItem->uri(), layerItem->uri(), layerItem->providerKey() ) );
+    mLayer = qgis::make_unique < QgsMeshLayer >( layerItem->uri(), layerItem->uri(), layerItem->providerKey() );
-    if ( layer )
-    {
-      if ( layer->isValid() )
-      {
-        bool ok = false;
-        layer->loadDefaultMetadata( ok );
-        layerCrs = layer->crs();
-        layerMetadata = layer->htmlMetadata();
-      }
-    }
   }
   else if ( type == QgsMapLayer::VectorLayer )
   {
     QgsDebugMsg( QStringLiteral( "creating vector layer" ) );
-    std::unique_ptr<QgsVectorLayer> layer( new QgsVectorLayer( layerItem->uri(), layerItem->name(), layerItem->providerKey() ) );
+    mLayer = qgis::make_unique < QgsVectorLayer>( layerItem->uri(), layerItem->name(), layerItem->providerKey() );
-    if ( layer )
-    {
-      if ( layer->isValid() )
-      {
-        bool ok = false;
-        layer->loadDefaultMetadata( ok );
-        layerCrs = layer->crs();
-        layerMetadata = layer->htmlMetadata();
-      }
-    }
   }
   else if ( type == QgsMapLayer::PluginLayer )
   {
@@ -215,11 +201,23 @@ void QgsBrowserLayerProperties::setItem( QgsDataItem *item )
     return;
   }
 
+  if ( mLayer && mLayer->isValid() )
+  {
+    bool ok = false;
+    mLayer->loadDefaultMetadata( ok );
+    layerCrs = mLayer->crs();
+    layerMetadata = mLayer->htmlMetadata();
+
+    mMapCanvas->setDestinationCrs( mLayer->crs() );
+    mMapCanvas->setLayers( QList< QgsMapLayer * >() << mLayer.get() );
+    mMapCanvas->zoomToFullExtent();
+  }
+
   QString myStyle = QgsApplication::reportStyleSheet();
   mMetadataTextBrowser->document()->setDefaultStyleSheet( myStyle );
   mMetadataTextBrowser->setHtml( layerMetadata );
 
-  // report if layer was set to to project crs without prompt (may give a false positive)
+// report if layer was set to to project crs without prompt (may give a false positive)
   if ( defaultProjectionOption == QLatin1String( "prompt" ) )
   {
     QgsCoordinateReferenceSystem defaultCrs =

src/gui/qgsbrowserdockwidget_p.h

@@ -126,6 +126,10 @@ class QgsBrowserLayerProperties : public QgsBrowserPropertiesWidget, private Ui:
   private slots:
 
     void urlClicked( const QUrl &url );
+
+  private:
+    std::unique_ptr<QgsMapLayer> mLayer;
+
 };
 
 /**

src/gui/qgsmapcanvas.cpp

@@ -174,7 +174,7 @@ QgsMapCanvas::QgsMapCanvas( QWidget *parent )
   // keep device pixel ratio up to date on screen or resolution change
   connect( window()->windowHandle(), &QWindow::screenChanged, this, [ = ]( QScreen * ) {mSettings.setDevicePixelRatio( devicePixelRatio() );} );
   if ( window()->windowHandle() )
-    connect( window()->windowHandle()->screen(), &QScreen::physicalDotsPerInchChanged, [ = ]( qreal ) {mSettings.setDevicePixelRatio( devicePixelRatio() );} );
+    connect( window()->windowHandle()->screen(), &QScreen::physicalDotsPerInchChanged, this, [ = ]( qreal ) {mSettings.setDevicePixelRatio( devicePixelRatio() );} );
 
   connect( &mMapUpdateTimer, &QTimer::timeout, this, &QgsMapCanvas::mapUpdateTimeout );
   mMapUpdateTimer.setInterval( 250 );

src/ui/qgsbrowserlayerpropertiesbase.ui

@@ -24,7 +24,58 @@
     <number>0</number>
    </property>
    <item>
-    <widget class="QTextBrowser" name="mMetadataTextBrowser"/>
+    <widget class="QTabWidget" name="mTabWidget">
+     <property name="tabShape">
+      <enum>QTabWidget::Rounded</enum>
+     </property>
+     <property name="currentIndex">
+      <number>0</number>
+     </property>
+     <widget class="QWidget" name="tab">
+      <attribute name="title">
+       <string>Metadata</string>
+      </attribute>
+      <layout class="QVBoxLayout" name="verticalLayout_2">
+       <property name="leftMargin">
+        <number>0</number>
+       </property>
+       <property name="topMargin">
+        <number>0</number>
+       </property>
+       <property name="rightMargin">
+        <number>0</number>
+       </property>
+       <property name="bottomMargin">
+        <number>0</number>
+       </property>
+       <item>
+        <widget class="QTextBrowser" name="mMetadataTextBrowser"/>
+       </item>
+      </layout>
+     </widget>
+     <widget class="QWidget" name="mPreviewTab">
+      <attribute name="title">
+       <string>Preview</string>
+      </attribute>
+      <layout class="QHBoxLayout" name="horizontalLayout">
+       <property name="leftMargin">
+        <number>0</number>
+       </property>
+       <property name="topMargin">
+        <number>0</number>
+       </property>
+       <property name="rightMargin">
+        <number>0</number>
+       </property>
+       <property name="bottomMargin">
+        <number>0</number>
+       </property>
+       <item>
+        <widget class="QgsMapCanvas" name="mMapCanvas" native="true"/>
+       </item>
+      </layout>
+     </widget>
+    </widget>
    </item>
    <item>
     <widget class="QLabel" name="mNoticeLabel">
@@ -38,9 +89,14 @@
    </item>
   </layout>
  </widget>
- <tabstops>
+ <customwidgets>
-  <tabstop>mMetadataTextBrowser</tabstop>
+  <customwidget>
- </tabstops>
+   <class>QgsMapCanvas</class>
+   <extends>QWidget</extends>
+   <header>qgsmapcanvas.h</header>
+   <container>1</container>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections/>
 </ui>