[FEATURE]: Apply patch from Stefan Ziegler which adds the option to select decimals places and + signs for numeric labels. Thanks\!

src/app/qgslabelinggui.cpp

@@ -145,6 +145,20 @@ QgsLabelingGui::QgsLabelingGui( QgsPalLabeling* lbl, QgsVectorLayer* layer, QgsM
   btnTextColor->setColor( lyr.textColor );
   btnBufferColor->setColor( lyr.bufferColor );
 
+  bool formattedNumbers = lyr.formatNumbers;
+  bool plusSign = lyr.plusSign;
+
+  chkFormattedNumbers->setChecked( formattedNumbers );
+  if ( formattedNumbers )
+  {
+    spinDecimals->setValue( lyr.decimals );
+  }
+  if ( plusSign )
+  {
+    chkPlusSign->setChecked( plusSign );
+  }
+
+
   if ( lyr.fontSizeInMapUnits )
   {
     mFontSizeUnitComboBox->setCurrentIndex( 1 );
@@ -163,6 +177,7 @@ QgsLabelingGui::QgsLabelingGui( QgsPalLabeling* lbl, QgsVectorLayer* layer, QgsM
 
   connect( chkBuffer, SIGNAL( toggled( bool ) ), this, SLOT( updateUi() ) );
   connect( chkScaleBasedVisibility, SIGNAL( toggled( bool ) ), this, SLOT( updateUi() ) );
+  connect( chkFormattedNumbers, SIGNAL( toggled( bool ) ), this, SLOT( updateUi() ) );
 
   // setup connection to changes in the placement
   QRadioButton* placementRadios[] =
@@ -269,6 +284,18 @@ QgsPalLayerSettings QgsLabelingGui::layerSettings()
   {
     lyr.bufferSize = 0;
   }
+  if ( chkFormattedNumbers->isChecked() )
+  {
+    lyr.formatNumbers = true;
+    lyr.decimals = spinDecimals->value();
+    lyr.plusSign = chkPlusSign->isChecked();
+  }
+  else
+  {
+    lyr.formatNumbers = false;
+    lyr.decimals = spinDecimals->value();
+    lyr.plusSign = true;
+  }
   if ( chkAddDirectionSymbol->isChecked() )
   {
     lyr.addDirectionSymbol = true;
@@ -451,7 +478,7 @@ void QgsLabelingGui::showEngineConfigDialog()
 
 void QgsLabelingGui::updateUi()
 {
-  // enable/disable scale-based, buffer
+  // enable/disable scale-based, buffer, decimals
   bool buf = chkBuffer->isChecked();
   spinBufferSize->setEnabled( buf );
   btnBufferColor->setEnabled( buf );
@@ -459,6 +486,8 @@ void QgsLabelingGui::updateUi()
   bool scale = chkScaleBasedVisibility->isChecked();
   spinScaleMin->setEnabled( scale );
   spinScaleMax->setEnabled( scale );
+
+  spinDecimals->setEnabled( chkFormattedNumbers->isChecked() );
 }
 
 void QgsLabelingGui::changeBufferColor()

src/core/pal/feature.cpp

@@ -40,7 +40,6 @@
 
 #include <qglobal.h>
 
-
 #include <cmath>
 #include <cstring>
 #include <cfloat>

src/core/qgspallabeling.cpp

@@ -145,6 +145,9 @@ QgsPalLayerSettings::QgsPalLayerSettings()
   scaleMax = 0;
   bufferSize = 1;
   bufferColor = Qt::white;
+  formatNumbers = false;
+  decimals = 3;
+  plusSign = false;
   labelPerPart = false;
   mergeLines = false;
   multiLineLabels = false;
@@ -172,6 +175,9 @@ QgsPalLayerSettings::QgsPalLayerSettings( const QgsPalLayerSettings& s )
   scaleMax = s.scaleMax;
   bufferSize = s.bufferSize;
   bufferColor = s.bufferColor;
+  formatNumbers = s.formatNumbers;
+  decimals = s.decimals;
+  plusSign = s.plusSign;
   labelPerPart = s.labelPerPart;
   mergeLines = s.mergeLines;
   multiLineLabels = s.multiLineLabels;
@@ -303,6 +309,9 @@ void QgsPalLayerSettings::readFromLayer( QgsVectorLayer* layer )
   scaleMax = layer->customProperty( "labeling/scaleMax" ).toInt();
   bufferSize = layer->customProperty( "labeling/bufferSize" ).toDouble();
   bufferColor = _readColor( layer, "labeling/bufferColor" );
+  formatNumbers = layer->customProperty( "labeling/formatNumbers" ).toBool();
+  decimals = layer->customProperty( "labeling/decimals" ).toInt();
+  plusSign = layer->customProperty( "labeling/plussign" ).toInt();
   labelPerPart = layer->customProperty( "labeling/labelPerPart" ).toBool();
   mergeLines = layer->customProperty( "labeling/mergeLines" ).toBool();
   multiLineLabels = layer->customProperty( "labeling/multiLineLabels" ).toBool();
@@ -338,6 +347,9 @@ void QgsPalLayerSettings::writeToLayer( QgsVectorLayer* layer )
   layer->setCustomProperty( "labeling/scaleMax", scaleMax );
   layer->setCustomProperty( "labeling/bufferSize", bufferSize );
   _writeColor( layer, "labeling/bufferColor", bufferColor );
+  layer->setCustomProperty( "labeling/formatNumbers", formatNumbers );
+  layer->setCustomProperty( "labeling/decimals", decimals );
+  layer->setCustomProperty( "labeling/plussign", plusSign );
   layer->setCustomProperty( "labeling/labelPerPart", labelPerPart );
   layer->setCustomProperty( "labeling/mergeLines", mergeLines );
   layer->setCustomProperty( "labeling/multiLineLabels", multiLineLabels );
@@ -437,7 +449,25 @@ void QgsPalLayerSettings::calculateLabelSize( const QFontMetricsF* fm, QString t
 
 void QgsPalLayerSettings::registerFeature( QgsFeature& f, const QgsRenderContext& context )
 {
-  QString labelText = f.attributeMap()[fieldIndex].toString();
+
+  QString labelText;
+  if ( formatNumbers == true
+       && ( f.attributeMap()[fieldIndex].type() == QVariant::Int || f.attributeMap()[fieldIndex].type() == QVariant::Double ) )
+  {
+    QString numberFormat;
+    double d = f.attributeMap()[fieldIndex].toDouble();
+    if ( d > 0 && plusSign == true )
+    {
+      numberFormat.append( "+" );
+    }
+    numberFormat.append( "%1" );
+    labelText = numberFormat.arg( d, 0, 'f', decimals );
+  }
+  else
+  {
+    labelText = f.attributeMap()[fieldIndex].toString();
+  }
+
   double labelX, labelY; // will receive label size
   QFont labelFont = textFont;
 

src/core/qgspallabeling.h

@@ -111,6 +111,9 @@ class CORE_EXPORT QgsPalLayerSettings
     int scaleMin, scaleMax; // disabled if both are zero
     double bufferSize; //buffer size (in mm)
     QColor bufferColor;
+    bool formatNumbers;
+    int decimals;
+    bool plusSign;
     bool labelPerPart; // whether to label every feature's part or only the biggest one
     bool mergeLines;
     bool multiLineLabels; //draw labels on multiple lines if they contain '\n'

src/ui/qgslabelingguibase.ui

@@ -372,6 +372,51 @@
          </layout>
         </widget>
        </item>
+       <item row="3" column="0">
+        <widget class="QGroupBox" name="chkFormattedNumbers">
+         <property name="title">
+          <string>Formatted numbers</string>
+         </property>
+         <property name="checkable">
+          <bool>true</bool>
+         </property>
+         <layout class="QGridLayout" name="gridLayout_15">
+          <item row="0" column="1">
+           <widget class="QSpinBox" name="spinDecimals"/>
+          </item>
+          <item row="0" column="3">
+           <spacer name="horizontalSpacer_4">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>468</width>
+              <height>20</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+          <item row="0" column="0">
+           <widget class="QLabel" name="label">
+            <property name="text">
+             <string>Deicmal places </string>
+            </property>
+           </widget>
+          </item>
+          <item row="0" column="2">
+           <widget class="QCheckBox" name="chkPlusSign">
+            <property name="layoutDirection">
+             <enum>Qt::RightToLeft</enum>
+            </property>
+            <property name="text">
+             <string>Show plus sign</string>
+            </property>
+           </widget>
+          </item>
+         </layout>
+        </widget>
+       </item>
       </layout>
      </widget>
      <widget class="QWidget" name="tab">
@@ -394,7 +439,7 @@
             <x>0</x>
             <y>0</y>
             <width>643</width>
-            <height>435</height>
+            <height>478</height>
            </rect>
           </property>
           <layout class="QGridLayout" name="gridLayout_13">
@@ -848,7 +893,7 @@
             <x>0</x>
             <y>0</y>
             <width>643</width>
-            <height>532</height>
+            <height>586</height>
            </rect>
           </property>
           <layout class="QGridLayout" name="gridLayout_11">