Update to freeze/thaw label tool

Added ability to hide label(s), i.e. set font size to 0, by holding Ctl (Cmd on Mac) modifier key.
This is a temporary convenience function, until there is a specifically mapped field for showing/hiding a label.
Silently fails if no font size field is mapped.

Dropped What's This? text in favor of concise tool tip for freeze/thaw tool.

Added self to CONTRIBUTORS. Stripped trailing whitespace from that file.

doc/CONTRIBUTORS

@@ -29,9 +29,10 @@ Giuseppe Sucameli
 Horst Duester
 Hyao (IRC nickname)
 Ivan Lucena
-Jean-Denis Giguere 
+Jean-Denis Giguere
 Jeremy Palmer
 Jerrit Collord
+Larry Shaffer
 Luiz Motta
 Magnus Homann
 Marco Pasetti
@@ -53,5 +54,5 @@ Tamas Szekeres
 Tom Russo
 Tyler Mitchell
 Vita Cizek
-Yann Chemin 
+Yann Chemin
 Includes Map icons CC-0 from SJJB Management

src/app/qgsmaptoolfreezelabels.cpp

@@ -258,6 +258,7 @@ void QgsMapToolFreezeLabels::freezeThawLabels( const QgsRectangle& ext, QMouseEv
 
   bool doThaw = e->modifiers() & Qt::ShiftModifier ? true : false;
   bool toggleThawOrFreeze = e->modifiers() & Qt::AltModifier ? true : false;
+  bool doHide = e->modifiers() & Qt::ControlModifier ? true : false;
 
   // get list of all drawn labels from all layers within, or touching, chosen extent
   bool labelChanged = false;
@@ -314,9 +315,8 @@ void QgsMapToolFreezeLabels::freezeThawLabels( const QgsRectangle& ext, QMouseEv
     QString labelStringID = QString("%0|%1").arg(mCurrentLabelPos.layerID, QString::number( mCurrentLabelPos.featureId ) );
 
     // thaw label
-    if ( mCurrentLabelPos.isFrozen && ( doThaw  || toggleThawOrFreeze  ) )
+    if ( mCurrentLabelPos.isFrozen && !doHide && ( doThaw  || toggleThawOrFreeze  ) )
     {
-
       // thaw previously frozen label (set attribute table fields to NULL)
       if ( freezeThawLabel( vlayer, mCurrentLabelPos, false ) )
       {
@@ -329,9 +329,8 @@ void QgsMapToolFreezeLabels::freezeThawLabels( const QgsRectangle& ext, QMouseEv
     }
 
     // freeze label
-    if ( !mCurrentLabelPos.isFrozen && ( !doThaw || toggleThawOrFreeze ) )
+    if ( !mCurrentLabelPos.isFrozen && !doHide && ( !doThaw || toggleThawOrFreeze ) )
     {
-
       // freeze label's location, and optionally rotation, to attribute table
       if ( freezeThawLabel( vlayer, mCurrentLabelPos, true ) )
       {
@@ -342,6 +341,20 @@ void QgsMapToolFreezeLabels::freezeThawLabels( const QgsRectangle& ext, QMouseEv
         QgsDebugMsg( QString( "Freeze failed for layer, label: %0, %1" ).arg( labellyr, labeltxt ) );
       }
     }
+
+    // hide label
+    if ( doHide )
+    {
+      // write 0 font size to attribute table
+      if ( hideLabel( vlayer, mCurrentLabelPos ) )
+      {
+        labelChanged = true;
+      }
+      else
+      {
+        QgsDebugMsg( QString( "Hide failed for layer, label: %0, %1" ).arg( labellyr, labeltxt ) );
+      }
+    }
   }
 
   if ( labelChanged )
@@ -479,3 +492,42 @@ bool QgsMapToolFreezeLabels::freezeThawLabel( QgsVectorLayer* vlayer,
   }
   return true;
 }
+
+bool QgsMapToolFreezeLabels::hideLabel( QgsVectorLayer* vlayer,
+                                        const QgsLabelPosition& labelpos )
+{
+  // skip diagrams
+  if ( labelpos.isDiagram )
+  {
+    QgsDebugMsg( QString( "Label is diagram, skipping" ) );
+    return false;
+  }
+  // verify attribute table has proper fields setup
+  bool sizeColOk;
+  int sizeCol;
+
+  QVariant sizeColumn = vlayer->customProperty( "labeling/dataDefinedProperty0" );
+  if ( !sizeColumn.isValid() )
+  {
+    QgsDebugMsg( QString( "Size column not set" ) );
+    return false;
+  }
+  sizeCol = sizeColumn.toInt( &sizeColOk );
+  if ( !sizeColOk )
+  {
+    QgsDebugMsg( QString( "Size column not convertible to integer" ) );
+    return false;
+  }
+
+  // edit attribute table
+  int fid = labelpos.featureId;
+
+  vlayer->beginEditCommand( tr( "Label hidden" ) );
+  if ( !vlayer->changeAttributeValue( fid, sizeCol, 0, false ) )
+  {
+    QgsDebugMsg( QString( "Failed write to attribute table" ) );
+    return false;
+  }
+  vlayer->endEditCommand();
+  return true;
+}

src/app/qgsmaptoolfreezelabels.h

@@ -95,6 +95,9 @@ class QgsMapToolFreezeLabels: public QgsMapToolLabel
     bool freezeThawLabel( QgsVectorLayer* vlayer,
                           const QgsLabelPosition& labelpos,
                           bool freeze );
+
+    //! Hide chosen label by setting font size to 0
+    bool hideLabel( QgsVectorLayer* vlayer, const QgsLabelPosition& labelpos );
 };
 
 #endif // QGSMAPTOOLFREEZELABELS_H

src/ui/qgisapp.ui

@@ -1716,13 +1716,9 @@
    <property name="text">
     <string>Freeze or Thaw Labels</string>
    </property>
-   <property name="whatsThis">
-    <string>Freeze (write label location and optionally rotation) to attribute table.
-
-Click on individual labels, or draw a marquee (labels touching will be included). Actions on in-memory attribute table fields are immediate.
-
-Hold Shift key down to Thaw (write NULLs to attribute table), reverting label to dynamic.
-Hold Alt key down to toggle selected labels between Frozen and Thawed states.</string>
+   <property name="toolTip">
+    <string>Freeze or Thaw Labels
+Shift thaws, Alt toggles, Ctl (Cmd) hides</string>
    </property>
   </action>
   <action name="mActionShowFrozenLabels">