Index: src/core/qgsvectorlayer.cpp
===================================================================
--- src/core/qgsvectorlayer.cpp	(revision 11856)
+++ src/core/qgsvectorlayer.cpp	(working copy)
@@ -646,6 +646,11 @@
   return ptr;
 }
 
+void QgsVectorLayer::run( )
+{
+    draw( mRenderContext );
+}
+
 bool QgsVectorLayer::draw( QgsRenderContext& rendererContext )
 {
   //set update threshold before each draw to make sure the current setting is picked up
Index: src/core/raster/qgsrasterlayer.cpp
===================================================================
--- src/core/raster/qgsrasterlayer.cpp	(revision 11856)
+++ src/core/raster/qgsrasterlayer.cpp	(working copy)
@@ -1343,6 +1343,11 @@
   return mDataProvider;
 }
 
+void QgsRasterLayer::run( )
+{
+    draw( mRenderContext );
+}
+
 bool QgsRasterLayer::draw( QgsRenderContext& rendererContext )
 {
   QgsDebugMsg( "entered. (renderContext)" );
Index: src/core/raster/qgsrasterlayer.h
===================================================================
--- src/core/raster/qgsrasterlayer.h	(revision 11856)
+++ src/core/raster/qgsrasterlayer.h	(working copy)
@@ -455,6 +455,11 @@
     /** Returns the data provider in a const-correct manner */
     const QgsRasterDataProvider* dataProvider() const;
 
+    /** Render the layer in a thread.
+     * @note Added in QGIS 1.4
+     */
+    void run();
+
     /** \brief This is called when the view on the raster layer needs to be redrawn */
     bool draw( QgsRenderContext& rendererContext );
 
Index: src/core/qgsmaplayer.cpp
===================================================================
--- src/core/qgsmaplayer.cpp	(revision 11856)
+++ src/core/qgsmaplayer.cpp	(working copy)
@@ -133,6 +133,16 @@
   return mLayerExtent;
 }
 
+void  QgsMapLayer::setRenderContext( QgsRenderContext theContext )
+{
+  mRenderContext = theContext;
+}
+
+void QgsMapLayer::run( )
+{
+  return ;
+}
+
 bool QgsMapLayer::draw( QgsRenderContext& rendererContext )
 {
   return false;
Index: src/core/qgsvectorlayer.h
===================================================================
--- src/core/qgsvectorlayer.h	(revision 11856)
+++ src/core/qgsvectorlayer.h	(working copy)
@@ -363,6 +363,10 @@
                          QgsSnappingResult > & snappingResults,
                          QgsSnapper::SnappingType snap_to );
 
+    /** Draw the layer in its own thread 
+     * @note - added in QGIS 1.4
+     */
+    void run();
     /** Draws the layer
      *  @return FALSE if an error occurred during drawing
      */
Index: src/core/qgsmaplayer.h
===================================================================
--- src/core/qgsmaplayer.h	(revision 11857)
+++ src/core/qgsmaplayer.h	(working copy)
@@ -25,10 +25,10 @@
 #include <QObject>
 #include <QUndoStack>
 #include <QImage>
+#include <QThread>
 
 #include "qgsrectangle.h"
 
-class QgsRenderContext;
 class QgsCoordinateReferenceSystem;
 
 class QDomNode;
@@ -36,13 +36,15 @@
 class QKeyEvent;
 class QPainter;
 
+#include "qgsrendercontext.h"
+
 /** \ingroup core
  * Base class for all map layer types.
  * This is the base class for all map layer types (vector, raster).
  */
-class CORE_EXPORT QgsMapLayer : public QObject
+class CORE_EXPORT QgsMapLayer : public QThread
 {
-    Q_OBJECT
+    Q_OBJECT;
 
   public:
     /** Layers enum defining the types of layers that can be added to a map */
@@ -79,11 +81,28 @@
      */
     QString const & name() const;
 
+    /** Render this layer onto the paint device 
+     * specified in mRenderContext in a separate thread.
+     *
+     * @note Added in QGIS 1.4
+     */
+    virtual void run();
+
+    /** Set the render context onto which the layer will
+     * be drawn when the thread is started.
+     * @see run()
+     * @note Added in QGIS 1.4
+     */
+    void setRenderContext( QgsRenderContext theContext );
+
     /** This is the method that does the actual work of 
      * drawing the layer onto a paint device.
      * @param QgsRenderContext - describes the extents, 
      * resolution etc. that should be used when rendering the 
      * layer.
+     * @note From QGIS 1.4 onwards for threaded drawing you should rather 
+     * use setRenderContext and then call run() rather than call this
+     * method which may be deprecated in the future.
      */
     virtual bool draw( QgsRenderContext& rendererContext );
 
@@ -381,6 +400,10 @@
      * @note This property was added in QGIS 1.4 **/
     QImage * mpCacheImage;
 
+  protected:
+    /** Render context defining the scale etc and paint device
+     * onto which the layer should be rendered when run is called. */
+    QgsRenderContext mRenderContext;
 };
 
 #endif