In the Identify results window, derived attributes such as Length or Area are now placed in a subtree of the attributes list called "(Derived)". This distinguishes them from explicit attributes that are a part of the user's layer.

If programmers wish to add more derived attributes in future, they can use the new QgsIdentifyResults::addDerivedAttribute() function.

This commit should address trac ticket #100.



git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@5592 c8812cc2-4d05-0410-92ff-de0c093fc19c

src/gui/qgsidentifyresults.cpp

@@ -31,7 +31,9 @@
 QgsIdentifyResults::QgsIdentifyResults(const QgsAttributeAction& actions,
     QWidget *parent, Qt::WFlags f)
 : QDialog(parent, f),
-  mActions(actions), mClickedOnValue(0), mActionPopup(0)
+  mActions(actions),
+  mClickedOnValue(0),
+  mActionPopup(0)
 {
   setupUi(this);
   lstResults->setResizeMode(Q3ListView::AllColumns);
@@ -157,16 +159,41 @@ void QgsIdentifyResults::saveWindowLocation()
   settings.writeEntry("/Windows/Identify/w", s.width());
   settings.writeEntry("/Windows/Identify/h", s.height());
 } 
+
 /** add an attribute and its value to the list */
 void QgsIdentifyResults::addAttribute(Q3ListViewItem * fnode, QString field, QString value)
 {
   new Q3ListViewItem(fnode, field, value);
 }
+
 void QgsIdentifyResults::addAttribute(QString field, QString value)
 {
   new Q3ListViewItem(lstResults, field, value);
 }
 
+void QgsIdentifyResults::addDerivedAttribute(Q3ListViewItem * fnode, QString field, QString value)
+{
+  // TODO: When we migrate this to a Qt4 QTreeViewWidget,
+  //       this should be added as italic text instead
+
+  Q3ListViewItem * daRootNode;
+
+  // Determine if this is the first derived attribute for this
+  // feature or not
+  if (mDerivedAttributeRootNodes.find(fnode) != mDerivedAttributeRootNodes.end())
+  {
+    // Reuse existing derived-attribute root node
+    daRootNode = mDerivedAttributeRootNodes[fnode];
+  }
+  else
+  {
+    // Create new derived-attribute root node
+    daRootNode = new Q3ListViewItem(fnode, tr("(Derived)"));
+  }
+
+  new Q3ListViewItem(daRootNode, field, value);
+}
+
 void QgsIdentifyResults::addAction(Q3ListViewItem * fnode, int id, QString field, QString value)
 {
   Q3ListViewItem *item = new Q3ListViewItem(fnode, field, value, "action", QString::number(id) );

src/gui/qgsidentifyresults.h

@@ -23,6 +23,7 @@
 #include "qgsattributeaction.h"
 #include <QWidget>
 #include <vector>
+#include <map>
 
 class QCloseEvent;
 class Q3ListViewItem;
@@ -43,11 +44,16 @@ class QgsIdentifyResults: public QDialog, private Ui::QgsIdentifyResultsBase
   QgsIdentifyResults(const QgsAttributeAction& actions, QWidget *parent = 0, Qt::WFlags f = 0);
 
   ~QgsIdentifyResults();
+
   /** Add an attribute to the feature display node */
   void addAttribute(Q3ListViewItem *parent, QString field, QString value);
+
   /** Add an attribute */
   void addAttribute(QString field, QString value);
 
+  /** Add a derived attribute (e.g. Length, Area) to the feature display node */
+  void addDerivedAttribute(Q3ListViewItem *parent, QString field, QString value);
+
   /** Add an action to the feature display node */
   void addAction(Q3ListViewItem *parent, int id, QString field, QString value);
 
@@ -90,6 +96,15 @@ class QgsIdentifyResults: public QDialog, private Ui::QgsIdentifyResultsBase
   int mClickedOnValue;
   QMenu* mActionPopup;
   std::vector<std::pair<QString, QString> > mValues;
+
+  /**
+   Keeps track of what derived-attribute (e.g. Length, Area)
+   root nodes have been generated for each feature in this widget.
+
+   First item:  Feature root node
+   Second item: Derived-attribute root node for that feature
+   */
+  std::map<Q3ListViewItem *, Q3ListViewItem *> mDerivedAttributeRootNodes;
 };
 
 #endif

src/gui/qgsmaptoolidentify.cpp

@@ -260,20 +260,21 @@ void QgsMapToolIdentify::identifyVectorLayer(QgsVectorLayer* layer, const QgsPoi
         mResults->addAttribute(featureNode, attr[i].fieldName(), attr[i].fieldValue());
       }
 
-      // measure distance or area
+      // Calculate derived attributes and insert:
+      // measure distance or area depending on geometry type
       if (layer->vectorType() == QGis::Line)
       {
         double dist = calc.measure(fet->geometry());
         QString str = QString::number(dist/1000, 'f', 3);
         str += " km";
-        mResults->addAttribute(featureNode, ".Length", str);
+        mResults->addDerivedAttribute(featureNode, QObject::tr("Length"), str);
       }
       else if (layer->vectorType() == QGis::Polygon)
       {
         double area = calc.measure(fet->geometry());
         QString str = QString::number(area/1000000, 'f', 3);
-        str += " km2";
-        mResults->addAttribute(featureNode, ".Area", str);
+        str += " km^2";
+        mResults->addDerivedAttribute(featureNode, QObject::tr("Area"), str);
       }
 
       // Add actions