X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;f=src%2Fjalview%2Fgui%2FSeqCanvas.java;h=1e1105f86d1a8413d931835502e8cd1a7e19ebb0;hb=f5cadfa2a55d78a08268a0df9a7c3f64d1c43e8a;hp=7eb356b8928404ccc4e1d6e30f5ce1a448f18210;hpb=eb86f84d1835ee5be41ebfef365a9e11021c16c2;p=jalview.git

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index 7eb356b..1e1105f 100755
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -31,6 +31,7 @@ import jalview.util.Comparison;
 import jalview.viewmodel.ViewportListenerI;
 import jalview.viewmodel.ViewportRanges;
 
+import java.awt.AlphaComposite;
 import java.awt.BasicStroke;
 import java.awt.BorderLayout;
 import java.awt.Color;
@@ -46,68 +47,58 @@ import java.util.List;
 import javax.swing.JComponent;
 
 /**
- * DOCUMENT ME!
+ * The Swing component on which the alignment sequences, and annotations (if
+ * shown), are drawn. This includes scales above, left and right (if shown) in
+ * Wrapped mode, but not the scale above in Unwrapped mode.
  * 
- * @author $author$
- * @version $Revision$
  */
 public class SeqCanvas extends JComponent implements ViewportListenerI
 {
-  private static String ZEROS = "0000000000";
+  private static final String ZEROS = "0000000000";
 
   final FeatureRenderer fr;
 
-  final SequenceRenderer sr;
-
   BufferedImage img;
 
-  Graphics2D gg;
-
-  int imgWidth;
-
-  int imgHeight;
-
   AlignViewport av;
 
-  boolean fastPaint = false;
-
-  boolean fastpainting = false;
-
   int cursorX = 0;
 
   int cursorY = 0;
 
-  int charHeight = 0;
+  private final SequenceRenderer seqRdr;
+
+  private boolean fastPaint = false;
 
-  int charWidth = 0;
+  private boolean fastpainting = false;
 
   private AnnotationPanel annotations;
 
   /*
    * measurements for drawing a wrapped alignment
    */
-  int labelWidthWest; // label left width in pixels if shown
-
   private int labelWidthEast; // label right width in pixels if shown
 
+  private int labelWidthWest; // label left width in pixels if shown
+
   private int wrappedSpaceAboveAlignment; // gap between widths
 
   private int wrappedRepeatHeightPx; // height in pixels of wrapped width
 
   private int wrappedVisibleWidths; // number of wrapped widths displayed
 
+  private Graphics2D gg;
+
   /**
    * Creates a new SeqCanvas object.
    * 
-   * @param av
-   *          DOCUMENT ME!
+   * @param ap
    */
   public SeqCanvas(AlignmentPanel ap)
   {
     this.av = ap.av;
-    updateViewport();
     fr = new FeatureRenderer(ap);
-    sr = new SequenceRenderer(av);
+    seqRdr = new SequenceRenderer(av);
     setLayout(new BorderLayout());
     PaintRefresher.Register(this, av.getSequenceSetId());
     setBackground(Color.white);
@@ -117,7 +108,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
   public SequenceRenderer getSequenceRenderer()
   {
-    return sr;
+    return seqRdr;
   }
 
   public FeatureRenderer getFeatureRenderer()
@@ -125,12 +116,6 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     return fr;
   }
 
-  private void updateViewport()
-  {
-    charHeight = av.getCharHeight();
-    charWidth = av.getCharWidth();
-  }
-
   /**
    * Draws the scale above a region of a wrapped alignment, consisting of a
    * column number every major interval (10 columns).
@@ -147,7 +132,8 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   private void drawNorthScale(Graphics g, int startx, int endx, int ypos)
   {
-    updateViewport();
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
 
     /*
      * white fill the scale space (for the fastPaint case)
@@ -189,6 +175,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    * Draw the scale to the left or right of a wrapped alignment
    * 
    * @param g
+   *          graphics context, positioned at the start of the scale to be drawn
    * @param startx
    *          first column of wrapped width (0.. excluding any hidden columns)
    * @param endx
@@ -198,16 +185,21 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    * @param left
    *          if true, scale is left of residues, if false, scale is right
    */
-  void drawVerticalScale(Graphics g, int startx, int endx, int ypos,
-          boolean left)
+  void drawVerticalScale(Graphics g, final int startx, final int endx,
+          final int ypos, final boolean left)
   {
-    ypos += charHeight;
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+
+    int yPos = ypos + charHeight;
+    int startX = startx;
+    int endX = endx;
 
     if (av.hasHiddenColumns())
     {
       HiddenColumns hiddenColumns = av.getAlignment().getHiddenColumns();
-      startx = hiddenColumns.adjustForHiddenColumns(startx);
-      endx = hiddenColumns.adjustForHiddenColumns(endx);
+      startX = hiddenColumns.adjustForHiddenColumns(startx);
+      endX = hiddenColumns.adjustForHiddenColumns(endx);
     }
     FontMetrics fm = getFontMetrics(av.getFont());
 
@@ -219,9 +211,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
        * find sequence position of first non-gapped position -
        * to the right if scale left, to the left if scale right
        */
-      int index = left ? startx : endx;
+      int index = left ? startX : endX;
       int value = -1;
-      while (index >= startx && index <= endx)
+      while (index >= startX && index <= endX)
       {
         if (!Comparison.isGap(seq.getCharAt(index)))
         {
@@ -242,28 +234,24 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
        * white fill the space for the scale
        */
       g.setColor(Color.white);
-      int y = (ypos + (i * charHeight)) - (charHeight / 5);
-      y -= charHeight; // fillRect: origin is top left of rectangle
-      int xpos = left ? 0 : labelWidthWest + charWidth
-              * av.getRanges().getViewportWidth();
-      g.fillRect(xpos, y, left ? labelWidthWest : labelWidthEast,
+      int y = (yPos + (i * charHeight)) - (charHeight / 5);
+      // fillRect origin is top left of rectangle
+      g.fillRect(0, y - charHeight, left ? labelWidthWest : labelWidthEast,
               charHeight + 1);
-      y += charHeight; // drawString: origin is bottom left of text
 
       if (value != -1)
       {
-
         /*
-         * draw scale value, right justified, with half a character width
-         * separation from the sequence data
+         * draw scale value, right justified within its width less half a
+         * character width padding on the right
          */
+        int labelSpace = left ? labelWidthWest : labelWidthEast;
+        labelSpace -= charWidth / 2; // leave space to the right
         String valueAsString = String.valueOf(value);
-        int justify = fm.stringWidth(valueAsString) + charWidth;
-        xpos = left ? labelWidthWest - justify + charWidth / 2
-                : getWidth() - justify - charWidth / 2;
-
+        int labelLength = fm.stringWidth(valueAsString);
+        int xOffset = labelSpace - labelLength;
         g.setColor(Color.black);
-        g.drawString(valueAsString, xpos, y);
+        g.drawString(valueAsString, xOffset, y);
       }
     }
   }
@@ -288,7 +276,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   public void fastPaint(int horizontal, int vertical)
   {
-    if (fastpainting || gg == null)
+    if (fastpainting || gg == null || img == null)
     {
       return;
     }
@@ -297,8 +285,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
     try
     {
-      updateViewport();
-
+      int charHeight = av.getCharHeight();
+      int charWidth = av.getCharWidth();
+    
       ViewportRanges ranges = av.getRanges();
       int startRes = ranges.getStartRes();
       int endRes = ranges.getEndRes();
@@ -307,8 +296,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       int transX = 0;
       int transY = 0;
 
-      gg.copyArea(horizontal * charWidth, vertical * charHeight, imgWidth,
-              imgHeight, -horizontal * charWidth, -vertical * charHeight);
+      gg.copyArea(horizontal * charWidth, vertical * charHeight,
+              img.getWidth(), img.getHeight(), -horizontal * charWidth,
+              -vertical * charHeight);
 
       if (horizontal > 0) // scrollbar pulled right, image to the left
       {
@@ -319,7 +309,8 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       {
         endRes = startRes - horizontal;
       }
-      else if (vertical > 0) // scroll down
+
+      if (vertical > 0) // scroll down
       {
         startSeq = endSeq - vertical;
 
@@ -329,7 +320,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         }
         else
         {
-          transY = imgHeight - ((vertical + 1) * charHeight);
+          transY = img.getHeight() - ((vertical + 1) * charHeight);
         }
       }
       else if (vertical < 0)
@@ -356,74 +347,217 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   @Override
   public void paintComponent(Graphics g)
   {
-    updateViewport();
-    BufferedImage lcimg = img; // take reference since other threads may null
-    // img and call later.
-    super.paintComponent(g);
+    super.paintComponent(g);    
+    
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+
+    ViewportRanges ranges = av.getRanges();
 
-    if (lcimg != null
-            && (fastPaint
-                    || (getVisibleRect().width != g.getClipBounds().width) || (getVisibleRect().height != g
-                    .getClipBounds().height)))
+    int width = getWidth();
+    int height = getHeight();
+
+    width -= (width % charWidth);
+    height -= (height % charHeight);
+
+    // selectImage is the selection group outline image
+    BufferedImage selectImage = drawSelectionGroup(
+            ranges.getStartRes(), ranges.getEndRes(),
+            ranges.getStartSeq(), ranges.getEndSeq());
+
+    if ((img != null) && (fastPaint
+            || (getVisibleRect().width != g.getClipBounds().width)
+            || (getVisibleRect().height != g.getClipBounds().height)))
     {
+      BufferedImage lcimg = buildLocalImage(selectImage);
       g.drawImage(lcimg, 0, 0, this);
       fastPaint = false;
-      return;
     }
+    else if ((width > 0) && (height > 0))
+    {
+      // img is a cached version of the last view we drew, if any
+      // if we have no img or the size has changed, make a new one
+      if (img == null || width != img.getWidth()
+              || height != img.getHeight())
+      {
+        img = setupImage();
+        if (img == null)
+        {
+          return;
+        }
+        gg = (Graphics2D) img.getGraphics();
+        gg.setFont(av.getFont());
+      }
+
+      if (av.antiAlias)
+      {
+        gg.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                RenderingHints.VALUE_ANTIALIAS_ON);
+      }
+
+      gg.setColor(Color.white);
+      gg.fillRect(0, 0, img.getWidth(), img.getHeight());
+
+      if (av.getWrapAlignment())
+      {
+        drawWrappedPanel(gg, getWidth(), getHeight(), ranges.getStartRes());
+      }
+      else
+      {
+        drawPanel(gg, ranges.getStartRes(), ranges.getEndRes(),
+                ranges.getStartSeq(), ranges.getEndSeq(), 0);
+      }
 
-    // this draws the whole of the alignment
-    imgWidth = getWidth();
-    imgHeight = getHeight();
+      // lcimg is a local *copy* of img which we'll draw selectImage on top of
+      BufferedImage lcimg = buildLocalImage(selectImage);
+      g.drawImage(lcimg, 0, 0, this);
 
-    imgWidth -= (imgWidth % charWidth);
-    imgHeight -= (imgHeight % charHeight);
+    }
 
-    if ((imgWidth < 1) || (imgHeight < 1))
+    if (av.cursorMode)
     {
-      return;
+      drawCursor(g, ranges.getStartRes(), ranges.getEndRes(),
+              ranges.getStartSeq(), ranges.getEndSeq());
     }
+  }
+  
+  /**
+   * Draw an alignment panel for printing
+   * 
+   * @param g1
+   *          Graphics object to draw with
+   * @param startRes
+   *          start residue of print area
+   * @param endRes
+   *          end residue of print area
+   * @param startSeq
+   *          start sequence of print area
+   * @param endSeq
+   *          end sequence of print area
+   */
+  public void drawPanelForPrinting(Graphics g1, int startRes, int endRes,
+          int startSeq, int endSeq)
+  {
+    drawPanel(g1, startRes, endRes, startSeq, endSeq, 0);
+
+    BufferedImage selectImage = drawSelectionGroup(startRes, endRes,
+            startSeq, endSeq);
+    if (selectImage != null)
+    {
+      ((Graphics2D) g1).setComposite(AlphaComposite
+              .getInstance(AlphaComposite.SRC_OVER));
+      g1.drawImage(selectImage, 0, 0, this);
+    }
+  }
+
+  /**
+   * Draw a wrapped alignment panel for printing
+   * 
+   * @param g
+   *          Graphics object to draw with
+   * @param canvasWidth
+   *          width of drawing area
+   * @param canvasHeight
+   *          height of drawing area
+   * @param startRes
+   *          start residue of print area
+   */
+  public void drawWrappedPanelForPrinting(Graphics g, int canvasWidth,
+          int canvasHeight, int startRes)
+  {
+    SequenceGroup group = av.getSelectionGroup();
 
-    if (lcimg == null || imgWidth != lcimg.getWidth()
-            || imgHeight != lcimg.getHeight())
+    drawWrappedPanel(g, canvasWidth, canvasHeight, startRes);
+
+    if (group != null)
     {
+      BufferedImage selectImage = null;
       try
       {
-        lcimg = img = new BufferedImage(imgWidth, imgHeight,
-                BufferedImage.TYPE_INT_RGB);
-        gg = (Graphics2D) img.getGraphics();
-        gg.setFont(av.getFont());
+        selectImage = new BufferedImage(canvasWidth, canvasHeight,
+                BufferedImage.TYPE_INT_ARGB); // ARGB so alpha compositing works
       } catch (OutOfMemoryError er)
       {
         System.gc();
-        System.err.println("SeqCanvas OutOfMemory Redraw Error.\n" + er);
-        new OOMWarning("Creating alignment image for display", er);
-
-        return;
+        System.err.println("Print image OutOfMemory Error.\n" + er);
+        new OOMWarning("Creating wrapped alignment image for printing", er);
+      }
+      if (selectImage != null)
+      {
+        Graphics2D g2 = selectImage.createGraphics();
+        setupSelectionGroup(g2, selectImage);
+        drawWrappedSelection(g2, group, canvasWidth, canvasHeight,
+                startRes);
+
+        g2.setComposite(
+                AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
+        g.drawImage(selectImage, 0, 0, this);
+        g2.dispose();
       }
     }
+  }
 
-    if (av.antiAlias)
+  /*
+   * Make a local image by combining the cached image img
+   * with any selection
+   */
+  private BufferedImage buildLocalImage(BufferedImage selectImage)
+  {
+    // clone the cached image
+    BufferedImage lcimg = new BufferedImage(img.getWidth(), img.getHeight(),
+            img.getType());
+    Graphics2D g2d = lcimg.createGraphics();
+    g2d.drawImage(img, 0, 0, null);
+
+    // overlay selection group on lcimg
+    if (selectImage != null)
     {
-      gg.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
-              RenderingHints.VALUE_ANTIALIAS_ON);
+      g2d.setComposite(
+              AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
+      g2d.drawImage(selectImage, 0, 0, this);
     }
 
-    gg.setColor(Color.white);
-    gg.fillRect(0, 0, imgWidth, imgHeight);
+    g2d.dispose();
 
-    ViewportRanges ranges = av.getRanges();
-    if (av.getWrapAlignment())
+    return lcimg;
+  }
+
+  /*
+   * Set up a buffered image of the correct height and size for the sequence canvas
+   */
+  private BufferedImage setupImage()
+  {
+    BufferedImage lcimg = null;
+
+    int charWidth = av.getCharWidth();
+    int charHeight = av.getCharHeight();
+    
+    int width = getWidth();
+    int height = getHeight();
+
+    width -= (width % charWidth);
+    height -= (height % charHeight);
+
+    if ((width < 1) || (height < 1))
     {
-      drawWrappedPanel(gg, getWidth(), getHeight(), ranges.getStartRes());
+      return null;
     }
-    else
+
+    try
     {
-      drawPanel(gg, ranges.getStartRes(), ranges.getEndRes(),
-              ranges.getStartSeq(), ranges.getEndSeq(), 0);
-    }
+      lcimg = new BufferedImage(width, height,
+              BufferedImage.TYPE_INT_ARGB); // ARGB so alpha compositing works
+    } catch (OutOfMemoryError er)
+    {
+      System.gc();
+      System.err.println(
+              "Group image OutOfMemory Redraw Error.\n" + er);
+      new OOMWarning("Creating alignment image for display", er);
 
-    g.drawImage(lcimg, 0, 0, this);
+      return null;
+    }
 
+    return lcimg;
   }
 
   /**
@@ -437,29 +571,30 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   public int getWrappedCanvasWidth(int canvasWidth)
   {
-    FontMetrics fm = getFontMetrics(av.getFont());
+    int charWidth = av.getCharWidth();
 
-    labelWidthEast = 0;
-    labelWidthWest = 0;
+    FontMetrics fm = getFontMetrics(av.getFont());
 
-    if (av.getScaleRightWrapped())
+    int labelWidth = 0;
+    
+    if (av.getScaleRightWrapped() || av.getScaleLeftWrapped())
     {
-      labelWidthEast = getLabelWidth(fm);
+      labelWidth = getLabelWidth(fm);
     }
 
-    if (av.getScaleLeftWrapped())
-    {
-      labelWidthWest = labelWidthEast > 0 ? labelWidthEast
-              : getLabelWidth(fm);
-    }
+    labelWidthEast = av.getScaleRightWrapped() ? labelWidth : 0;
+
+    labelWidthWest = av.getScaleLeftWrapped() ? labelWidth : 0;
 
     return (canvasWidth - labelWidthEast - labelWidthWest) / charWidth;
   }
 
   /**
-   * Returns a pixel width suitable for showing the largest sequence coordinate
-   * (end position) in the alignment. Returns 2 plus the number of decimal
-   * digits to be shown (3 for 1-10, 4 for 11-99 etc).
+   * Returns a pixel width sufficient to show the largest sequence coordinate
+   * (end position) in the alignment, calculated as the FontMetrics width of
+   * zeroes "0000000" limited to the number of decimal digits to be shown (3 for
+   * 1-10, 4 for 11-99 etc). One character width is added to this, to allow for
+   * half a character width space on either side.
    * 
    * @param fm
    * @return
@@ -477,13 +612,13 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       maxWidth = Math.max(maxWidth, alignment.getSequenceAt(i).getEnd());
     }
 
-    int length = 2;
+    int length = 0;
     for (int i = maxWidth; i > 0; i /= 10)
     {
       length++;
     }
 
-    return fm.stringWidth(ZEROS.substring(0, length));
+    return fm.stringWidth(ZEROS.substring(0, length)) + av.getCharWidth();
   }
 
   /**
@@ -501,8 +636,6 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   public void drawWrappedPanel(Graphics g, int canvasWidth,
           int canvasHeight, final int startColumn)
   {
-    updateViewport();
-
     int wrappedWidthInResidues = calculateWrappedGeometry(canvasWidth,
             canvasHeight);
 
@@ -515,20 +648,19 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
      * draw one width at a time (including any scales or annotation shown),
      * until we have run out of either alignment or vertical space available
      */
-    int yposMax = canvasHeight;
-    // ensure room for at least one sequence
-    yposMax -= wrappedSpaceAboveAlignment - charHeight;
     int ypos = wrappedSpaceAboveAlignment;
     int maxWidth = ranges.getVisibleAlignmentWidth();
 
     int start = startColumn;
-    while ((ypos <= yposMax) && (start < maxWidth))
+    int currentWidth = 0;
+    while ((currentWidth < wrappedVisibleWidths) && (start < maxWidth))
     {
       int endColumn = Math
               .min(maxWidth, start + wrappedWidthInResidues - 1);
       drawWrappedWidth(g, ypos, start, endColumn, canvasHeight);
       ypos += wrappedRepeatHeightPx;
       start += wrappedWidthInResidues;
+      currentWidth++;
     }
 
     drawWrappedDecorators(g, startColumn);
@@ -550,20 +682,11 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   protected int calculateWrappedGeometry(int canvasWidth, int canvasHeight)
   {
-    /*
-     * width of labels in pixels left and right (if shown)
-     */
-    int labelWidth = 0;
-    if (av.getScaleRightWrapped() || av.getScaleLeftWrapped())
-    {
-      FontMetrics fm = getFontMetrics(av.getFont());
-      labelWidth = getLabelWidth(fm);
-    }
-    labelWidthEast = av.getScaleRightWrapped() ? labelWidth : 0;
-    labelWidthWest = av.getScaleLeftWrapped() ? labelWidth : 0;
+    int charHeight = av.getCharHeight();
 
     /*
      * vertical space in pixels between wrapped widths of alignment
+     * - one character height, or two if scale above is drawn
      */
     wrappedSpaceAboveAlignment = charHeight
             * (av.getScaleAboveWrapped() ? 2 : 1);
@@ -573,15 +696,16 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
      */
     wrappedRepeatHeightPx = wrappedSpaceAboveAlignment;
     // add sequences
-    wrappedRepeatHeightPx += av.getRanges().getViewportHeight() * charHeight;
+    wrappedRepeatHeightPx += av.getRanges().getViewportHeight()
+            * charHeight;
     // add annotations panel height if shown
     wrappedRepeatHeightPx += getAnnotationHeight();
 
     /*
-     * number of visible widths (the last one may be part height)
+     * number of visible widths (the last one may be part height),
+     * ensuring a part height includes at least one sequence
      */
     ViewportRanges ranges = av.getRanges();
-    int xMax = ranges.getVisibleAlignmentWidth();
     wrappedVisibleWidths = canvasHeight / wrappedRepeatHeightPx;
     int remainder = canvasHeight % wrappedRepeatHeightPx;
     if (remainder >= (wrappedSpaceAboveAlignment + charHeight))
@@ -590,21 +714,22 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     }
 
     /*
+     * compute width in residues; this also sets East and West label widths
+     */
+    int wrappedWidthInResidues = getWrappedCanvasWidth(canvasWidth);
+
+    /*
      *  limit visibleWidths to not exceed width of alignment
      */
-    int viewportWidth = ranges.getViewportWidth();
-    int maxWidths = (xMax - ranges.getStartRes()) / viewportWidth;
-    if (xMax % viewportWidth > 0)
+    int xMax = ranges.getVisibleAlignmentWidth();
+    int startToEnd = xMax - ranges.getStartRes();
+    int maxWidths = startToEnd / wrappedWidthInResidues;
+    if (startToEnd % wrappedWidthInResidues > 0)
     {
       maxWidths++;
     }
     wrappedVisibleWidths = Math.min(wrappedVisibleWidths, maxWidths);
 
-    /*
-     * number of whole width residue columns we can show in each row
-     */
-    int wrappedWidthInResidues = (canvasWidth - labelWidthEast - labelWidthWest)
-            / charWidth;
     return wrappedWidthInResidues;
   }
 
@@ -618,8 +743,8 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    * @param endColumn
    * @param canvasHeight
    */
-  protected void drawWrappedWidth(Graphics g, int ypos,
-          int startColumn, int endColumn, int canvasHeight)
+  protected void drawWrappedWidth(Graphics g, int ypos, int startColumn,
+          int endColumn, int canvasHeight)
   {
     ViewportRanges ranges = av.getRanges();
     int viewportWidth = ranges.getViewportWidth();
@@ -628,9 +753,10 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
     /*
      * move right before drawing by the width of the scale left (if any)
-     * plus column offset from left margin (usually zero, but may not be
-     * when fast painting draws just a few columns)
+     * plus column offset from left margin (usually zero, but may be non-zero
+     * when fast painting is drawing just a few columns)
      */
+    int charWidth = av.getCharWidth();
     int xOffset = labelWidthWest
             + ((startColumn - ranges.getStartRes()) % viewportWidth)
             * charWidth;
@@ -650,10 +776,18 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
               viewportWidth * charWidth, (int) clip.getBounds().getHeight());
     }
 
+    /*
+     * white fill the region to be drawn (so incremental fast paint doesn't
+     * scribble over an existing image)
+     */
+    g.setColor(Color.white);
+    g.fillRect(0, ypos, (endx - startColumn + 1) * charWidth,
+            wrappedRepeatHeightPx);
+
     drawPanel(g, startColumn, endx, 0, av.getAlignment().getHeight() - 1,
             ypos);
 
-    int cHeight = av.getAlignment().getHeight() * charHeight;
+    int cHeight = av.getAlignment().getHeight() * av.getCharHeight();
 
     if (av.isShowAnnotation())
     {
@@ -678,8 +812,10 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    * @param g
    * @param startColumn
    */
-  protected void drawWrappedDecorators(Graphics g, int startColumn)
+  protected void drawWrappedDecorators(Graphics g, final int startColumn)
   {
+    int charWidth = av.getCharWidth();
+
     g.setFont(av.getFont());
     g.setColor(Color.black);
 
@@ -688,50 +824,60 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     int viewportWidth = ranges.getViewportWidth();
     int maxWidth = ranges.getVisibleAlignmentWidth();
     int widthsDrawn = 0;
+    int startCol = startColumn;
+
     while (widthsDrawn < wrappedVisibleWidths)
     {
-      int endColumn = Math.min(maxWidth, startColumn + viewportWidth - 1);
+      int endColumn = Math.min(maxWidth, startCol + viewportWidth - 1);
 
       if (av.getScaleLeftWrapped())
       {
-        drawVerticalScale(g, startColumn, endColumn - 1, ypos, true);
+        drawVerticalScale(g, startCol, endColumn - 1, ypos, true);
       }
 
       if (av.getScaleRightWrapped())
       {
-        drawVerticalScale(g, startColumn, endColumn, ypos, false);
+        int x = labelWidthWest + viewportWidth * charWidth;
+        g.translate(x, 0);
+        drawVerticalScale(g, startCol, endColumn, ypos, false);
+        g.translate(-x, 0);
       }
 
-      g.translate(labelWidthWest, 0);
-
       /*
        * white fill region of scale above and hidden column markers
        * (to support incremental fast paint of image)
        */
+      g.translate(labelWidthWest, 0);
       g.setColor(Color.white);
       g.fillRect(0, ypos - wrappedSpaceAboveAlignment, viewportWidth
-              * charWidth, wrappedSpaceAboveAlignment);
+              * charWidth + labelWidthWest, wrappedSpaceAboveAlignment);
       g.setColor(Color.black);
+      g.translate(-labelWidthWest, 0);
+
+      g.translate(labelWidthWest, 0);
 
       if (av.getScaleAboveWrapped())
       {
-        drawNorthScale(g, startColumn, endColumn, ypos);
+        drawNorthScale(g, startCol, endColumn, ypos);
       }
 
       if (av.hasHiddenColumns() && av.getShowHiddenMarkers())
       {
-        drawHiddenColumnMarkers(g, ypos, startColumn, endColumn);
+        drawHiddenColumnMarkers(g, ypos, startCol, endColumn);
       }
 
       g.translate(-labelWidthWest, 0);
 
       ypos += wrappedRepeatHeightPx;
-      startColumn += viewportWidth;
+      startCol += viewportWidth;
       widthsDrawn++;
     }
   }
 
   /**
+   * Draws markers (triangles) above hidden column positions between startColumn
+   * and endColumn.
+   * 
    * @param g
    * @param ypos
    * @param startColumn
@@ -740,6 +886,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   protected void drawHiddenColumnMarkers(Graphics g, int ypos,
           int startColumn, int endColumn)
   {
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+
     g.setColor(Color.blue);
     HiddenColumns hidden = av.getAlignment().getHiddenColumns();
     List<Integer> positions = hidden.findHiddenRegionPositions();
@@ -747,7 +896,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     {
       int res = pos - startColumn;
 
-      if (res < 0 || res > endColumn - startColumn)
+      if (res < 0 || res > endColumn - startColumn + 1)
       {
         continue;
       }
@@ -761,7 +910,67 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
           xMiddle + charHeight / 4, xMiddle };
       int yTop = ypos - (charHeight / 2);
       int[] yPoints = new int[] { yTop, yTop, yTop + 8 };
-      gg.fillPolygon(xPoints, yPoints, 3);
+      g.fillPolygon(xPoints, yPoints, 3);
+    }
+  }
+
+  /*
+   * Draw a selection group over a wrapped alignment
+   */
+  private void drawWrappedSelection(Graphics2D g, SequenceGroup group,
+          int canvasWidth,
+          int canvasHeight, int startRes)
+  {
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+      
+    // height gap above each panel
+    int hgap = charHeight;
+    if (av.getScaleAboveWrapped())
+    {
+      hgap += charHeight;
+    }
+
+    int cWidth = (canvasWidth - labelWidthEast - labelWidthWest)
+            / charWidth;
+    int cHeight = av.getAlignment().getHeight() * charHeight;
+
+    int startx = startRes;
+    int endx;
+    int ypos = hgap; // vertical offset
+    int maxwidth = av.getAlignment().getWidth();
+
+    if (av.hasHiddenColumns())
+    {
+      maxwidth = av.getAlignment().getHiddenColumns()
+              .findColumnPosition(maxwidth);
+    }
+
+    // chop the wrapped alignment extent up into panel-sized blocks and treat
+    // each block as if it were a block from an unwrapped alignment
+    while ((ypos <= canvasHeight) && (startx < maxwidth))
+    {
+      // set end value to be start + width, or maxwidth, whichever is smaller
+      endx = startx + cWidth - 1;
+
+      if (endx > maxwidth)
+      {
+        endx = maxwidth;
+      }
+
+      g.translate(labelWidthWest, 0);
+
+      drawUnwrappedSelection(g, group, startx, endx, 0,
+              av.getAlignment().getHeight() - 1,
+              ypos);
+
+      g.translate(-labelWidthWest, 0);
+
+      // update vertical offset
+      ypos += cHeight + getAnnotationHeight() + hgap;
+
+      // update horizontal offset
+      startx += cWidth;
     }
   }
 
@@ -802,7 +1011,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   public void drawPanel(Graphics g1, final int startRes, final int endRes,
           final int startSeq, final int endSeq, final int yOffset)
   {
-    updateViewport();
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+
     if (!av.hasHiddenColumns())
     {
       draw(g1, startRes, endRes, startSeq, endSeq, yOffset);
@@ -892,8 +1103,11 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   private void draw(Graphics g, int startRes, int endRes, int startSeq,
           int endSeq, int offset)
   {
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+
     g.setFont(av.getFont());
-    sr.prepare(g, av.isRenderGaps());
+    seqRdr.prepare(g, av.isRenderGaps());
 
     SequenceI nextSeq;
 
@@ -908,13 +1122,13 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         // empty
         continue;
       }
-      sr.drawSequence(nextSeq, av.getAlignment().findAllGroups(nextSeq),
+      seqRdr.drawSequence(nextSeq, av.getAlignment().findAllGroups(nextSeq),
               startRes, endRes, offset + ((i - startSeq) * charHeight));
 
       if (av.isShowSequenceFeatures())
       {
-        fr.drawSequence(g, nextSeq, startRes, endRes, offset
-                + ((i - startSeq) * charHeight), false);
+        fr.drawSequence(g, nextSeq, startRes, endRes,
+                offset + ((i - startSeq) * charHeight), false);
       }
 
       /*
@@ -929,20 +1143,13 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         {
           for (int r = 0; r < visibleResults.length; r += 2)
           {
-            sr.drawHighlightedText(nextSeq, visibleResults[r],
+            seqRdr.drawHighlightedText(nextSeq, visibleResults[r],
                     visibleResults[r + 1], (visibleResults[r] - startRes)
                             * charWidth, offset
                             + ((i - startSeq) * charHeight));
           }
         }
       }
-
-      if (av.cursorMode && cursorY == i && cursorX >= startRes
-              && cursorX <= endRes)
-      {
-        sr.drawCursor(nextSeq, cursorX, (cursorX - startRes) * charWidth,
-                offset + ((i - startSeq) * charHeight));
-      }
     }
 
     if (av.getSelectionGroup() != null
@@ -961,15 +1168,11 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     // ///////////////////////////////////
     // Now outline any areas if necessary
     // ///////////////////////////////////
-    SequenceGroup group = av.getSelectionGroup();
 
-    int sx = -1;
-    int sy = -1;
-    int ex = -1;
+    SequenceGroup group = null;
     int groupIndex = -1;
-    int visWidth = (endRes - startRes + 1) * charWidth;
 
-    if ((group == null) && (av.getAlignment().getGroups().size() > 0))
+    if (av.getAlignment().getGroups().size() > 0)
     {
       group = av.getAlignment().getGroups().get(0);
       groupIndex = 0;
@@ -977,170 +1180,403 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
     if (group != null)
     {
+      g.setStroke(new BasicStroke());
+      g.setColor(group.getOutlineColour());
+      
       do
       {
-        int oldY = -1;
-        int i = 0;
-        boolean inGroup = false;
-        int top = -1;
-        int bottom = -1;
+        drawPartialGroupOutline(g, group, startRes, endRes, startSeq,
+                endSeq, offset);
+
+        groupIndex++;
+
+        g.setStroke(new BasicStroke());
 
-        for (i = startSeq; i <= endSeq; i++)
+        if (groupIndex >= av.getAlignment().getGroups().size())
         {
-          sx = (group.getStartRes() - startRes) * charWidth;
-          sy = offset + ((i - startSeq) * charHeight);
-          ex = (((group.getEndRes() + 1) - group.getStartRes()) * charWidth) - 1;
+          break;
+        }
 
-          if (sx + ex < 0 || sx > visWidth)
-          {
-            continue;
-          }
+        group = av.getAlignment().getGroups().get(groupIndex);
 
-          if ((sx <= (endRes - startRes) * charWidth)
-                  && group.getSequences(null).contains(
-                          av.getAlignment().getSequenceAt(i)))
-          {
-            if ((bottom == -1)
-                    && !group.getSequences(null).contains(
-                            av.getAlignment().getSequenceAt(i + 1)))
-            {
-              bottom = sy + charHeight;
-            }
+      } while (groupIndex < av.getAlignment().getGroups().size());
 
-            if (!inGroup)
-            {
-              if (((top == -1) && (i == 0))
-                      || !group.getSequences(null).contains(
-                              av.getAlignment().getSequenceAt(i - 1)))
-              {
-                top = sy;
-              }
+    }
 
-              oldY = sy;
-              inGroup = true;
+  }
 
-              if (group == av.getSelectionGroup())
-              {
-                g.setStroke(new BasicStroke(1, BasicStroke.CAP_BUTT,
-                        BasicStroke.JOIN_ROUND, 3f, new float[] { 5f, 3f },
-                        0f));
-                g.setColor(Color.RED);
-              }
-              else
-              {
-                g.setStroke(new BasicStroke());
-                g.setColor(group.getOutlineColour());
-              }
-            }
-          }
-          else
-          {
-            if (inGroup)
-            {
-              if (sx >= 0 && sx < visWidth)
-              {
-                g.drawLine(sx, oldY, sx, sy);
-              }
 
-              if (sx + ex < visWidth)
-              {
-                g.drawLine(sx + ex, oldY, sx + ex, sy);
-              }
+  /*
+   * Draw the selection group as a separate image and overlay
+   */
+  private BufferedImage drawSelectionGroup(int startRes, int endRes,
+          int startSeq, int endSeq)
+  {
+    // get a new image of the correct size
+    BufferedImage selectionImage = setupImage();
 
-              if (sx < 0)
-              {
-                ex += sx;
-                sx = 0;
-              }
+    if (selectionImage == null)
+    {
+      return null;
+    }
 
-              if (sx + ex > visWidth)
-              {
-                ex = visWidth;
-              }
+    SequenceGroup group = av.getSelectionGroup();
+    if (group == null)
+    {
+      // nothing to draw
+      return null;
+    }
 
-              else if (sx + ex >= (endRes - startRes + 1) * charWidth)
-              {
-                ex = (endRes - startRes + 1) * charWidth;
-              }
+    // set up drawing colour
+    Graphics2D g = (Graphics2D) selectionImage.getGraphics();
 
-              if (top != -1)
-              {
-                g.drawLine(sx, top, sx + ex, top);
-                top = -1;
-              }
+    setupSelectionGroup(g, selectionImage);
 
-              if (bottom != -1)
-              {
-                g.drawLine(sx, bottom, sx + ex, bottom);
-                bottom = -1;
-              }
+    if (!av.getWrapAlignment())
+    {
+      drawUnwrappedSelection(g, group, startRes, endRes, startSeq, endSeq,
+              0);
+    }
+    else
+    {
+      drawWrappedSelection(g, group, getWidth(), getHeight(),
+              av.getRanges().getStartRes());
+    }
 
-              inGroup = false;
-            }
-          }
-        }
+    g.dispose();
+    return selectionImage;
+  }
+
+  /**
+   * Draw the cursor as a separate image and overlay
+   * 
+   * @param startRes
+   *          start residue of area to draw cursor in
+   * @param endRes
+   *          end residue of area to draw cursor in
+   * @param startSeq
+   *          start sequence of area to draw cursor in
+   * @param endSeq
+   *          end sequence of are to draw cursor in
+   * @return a transparent image of the same size as the sequence canvas, with
+   *         the cursor drawn on it, if any
+   */
+  private void drawCursor(Graphics g, int startRes, int endRes,
+          int startSeq,
+          int endSeq)
+  {
+    // convert the cursorY into a position on the visible alignment
+    int cursor_ypos = cursorY;
+
+    // don't do work unless we have to
+    if (cursor_ypos >= startSeq && cursor_ypos <= endSeq)
+    {
+      int yoffset = 0;
+      int xoffset = 0;
+      int startx = startRes;
+      int endx = endRes;
 
-        if (inGroup)
+      // convert the cursorX into a position on the visible alignment
+      int cursor_xpos = av.getAlignment().getHiddenColumns()
+              .findColumnPosition(cursorX);
+
+      if (av.getAlignment().getHiddenColumns().isVisible(cursorX))
+      {
+
+        if (av.getWrapAlignment())
         {
-          sy = offset + ((i - startSeq) * charHeight);
-          if (sx >= 0 && sx < visWidth)
+          // work out the correct offsets for the cursor
+          int charHeight = av.getCharHeight();
+          int charWidth = av.getCharWidth();
+          int canvasWidth = getWidth();
+          int canvasHeight = getHeight();
+
+          // height gap above each panel
+          int hgap = charHeight;
+          if (av.getScaleAboveWrapped())
           {
-            g.drawLine(sx, oldY, sx, sy);
+            hgap += charHeight;
           }
 
-          if (sx + ex < visWidth)
-          {
-            g.drawLine(sx + ex, oldY, sx + ex, sy);
-          }
+          int cWidth = (canvasWidth - labelWidthEast - labelWidthWest)
+                  / charWidth;
+          int cHeight = av.getAlignment().getHeight() * charHeight;
 
-          if (sx < 0)
-          {
-            ex += sx;
-            sx = 0;
-          }
+          endx = startx + cWidth - 1;
+          int ypos = hgap; // vertical offset
 
-          if (sx + ex > visWidth)
+          // iterate down the wrapped panels
+          while ((ypos <= canvasHeight) && (endx < cursor_xpos))
           {
-            ex = visWidth;
-          }
-          else if (sx + ex >= (endRes - startRes + 1) * charWidth)
-          {
-            ex = (endRes - startRes + 1) * charWidth;
-          }
+            // update vertical offset
+            ypos += cHeight + getAnnotationHeight() + hgap;
 
-          if (top != -1)
-          {
-            g.drawLine(sx, top, sx + ex, top);
-            top = -1;
+            // update horizontal offset
+            startx += cWidth;
+            endx = startx + cWidth - 1;
           }
+          yoffset = ypos;
+          xoffset = labelWidthWest;
+        }
 
-          if (bottom != -1)
-          {
-            g.drawLine(sx, bottom - 1, sx + ex, bottom - 1);
-            bottom = -1;
-          }
+        // now check if cursor is within range for x values
+        if (cursor_xpos >= startx && cursor_xpos <= endx)
+        {
+          // get the character the cursor is drawn at
+          SequenceI seq = av.getAlignment().getSequenceAt(cursorY);
+          char s = seq.getCharAt(cursorX);
 
-          inGroup = false;
+          seqRdr.drawCursor(g, s,
+                  xoffset + (cursor_xpos - startx) * av.getCharWidth(),
+                  yoffset + (cursor_ypos - startSeq) * av.getCharHeight());
         }
+      }
+    }
+  }
 
-        groupIndex++;
 
-        g.setStroke(new BasicStroke());
+  /*
+   * Set up graphics for selection group
+   */
+  private void setupSelectionGroup(Graphics2D g,
+          BufferedImage selectionImage)
+  {
+    // set background to transparent
+    g.setComposite(AlphaComposite.getInstance(AlphaComposite.CLEAR, 0.0f));
+    g.fillRect(0, 0, selectionImage.getWidth(), selectionImage.getHeight());
+
+    // set up foreground to draw red dashed line
+    g.setComposite(AlphaComposite.Src);
+    g.setStroke(new BasicStroke(1, BasicStroke.CAP_BUTT,
+            BasicStroke.JOIN_ROUND, 3f, new float[]
+    { 5f, 3f }, 0f));
+    g.setColor(Color.RED);
+  }
 
-        if (groupIndex >= av.getAlignment().getGroups().size())
+  /*
+   * Draw a selection group over an unwrapped alignment
+   * @param g graphics object to draw with
+   * @param group selection group
+   * @param startRes start residue of area to draw
+   * @param endRes end residue of area to draw
+   * @param startSeq start sequence of area to draw
+   * @param endSeq end sequence of area to draw
+   * @param offset vertical offset (used when called from wrapped alignment code)
+   */
+  private void drawUnwrappedSelection(Graphics2D g, SequenceGroup group,
+          int startRes, int endRes, int startSeq, int endSeq, int offset)
+  {
+    int charWidth = av.getCharWidth();
+          
+    if (!av.hasHiddenColumns())
+    {
+      drawPartialGroupOutline(g, group, startRes, endRes, startSeq, endSeq,
+              offset);
+    }
+    else
+    {
+      // package into blocks of visible columns
+      int screenY = 0;
+      int blockStart = startRes;
+      int blockEnd = endRes;
+
+      for (int[] region : av.getAlignment().getHiddenColumns()
+              .getHiddenColumnsCopy())
+      {
+        int hideStart = region[0];
+        int hideEnd = region[1];
+
+        if (hideStart <= blockStart)
+        {
+          blockStart += (hideEnd - hideStart) + 1;
+          continue;
+        }
+
+        blockEnd = hideStart - 1;
+
+        g.translate(screenY * charWidth, 0);
+        drawPartialGroupOutline(g, group,
+                blockStart, blockEnd, startSeq, endSeq, offset);
+
+        g.translate(-screenY * charWidth, 0);
+        screenY += blockEnd - blockStart + 1;
+        blockStart = hideEnd + 1;
+
+        if (screenY > (endRes - startRes))
         {
+          // already rendered last block
           break;
         }
+      }
 
-        group = av.getAlignment().getGroups().get(groupIndex);
+      if (screenY <= (endRes - startRes))
+      {
+        // remaining visible region to render
+        blockEnd = blockStart + (endRes - startRes) - screenY;
+        g.translate(screenY * charWidth, 0);
+        drawPartialGroupOutline(g, group,
+                blockStart, blockEnd, startSeq, endSeq, offset);
+        
+        g.translate(-screenY * charWidth, 0);
+      }
+    }
+  }
 
-      } while (groupIndex < av.getAlignment().getGroups().size());
+  /*
+   * Draw the selection group as a separate image and overlay
+   */
+  private void drawPartialGroupOutline(Graphics2D g, SequenceGroup group,
+          int startRes, int endRes, int startSeq, int endSeq,
+          int verticalOffset)
+  {
+    int charHeight = av.getCharHeight();
+    int charWidth = av.getCharWidth();
+    int visWidth = (endRes - startRes + 1) * charWidth;
+
+    int oldY = -1;
+    int i = 0;
+    boolean inGroup = false;
+    int top = -1;
+    int bottom = -1;
+    int sy = -1;
+
+    List<SequenceI> seqs = group.getSequences(null);
+
+    // position of start residue of group relative to startRes, in pixels
+    int sx = (group.getStartRes() - startRes) * charWidth;
+
+    // width of group in pixels
+    int xwidth = (((group.getEndRes() + 1) - group.getStartRes())
+            * charWidth) - 1;
+
+    if (!(sx + xwidth < 0 || sx > visWidth))
+    {
+      for (i = startSeq; i <= endSeq; i++)
+      {
+        sy = verticalOffset + (i - startSeq) * charHeight;
+
+        if ((sx <= (endRes - startRes) * charWidth)
+                && seqs.contains(av.getAlignment().getSequenceAt(i)))
+        {
+          if ((bottom == -1)
+                  && !seqs.contains(av.getAlignment().getSequenceAt(i + 1)))
+          {
+            bottom = sy + charHeight;
+          }
+
+          if (!inGroup)
+          {
+            if (((top == -1) && (i == 0)) || !seqs
+                    .contains(av.getAlignment().getSequenceAt(i - 1)))
+            {
+              top = sy;
+            }
+
+            oldY = sy;
+            inGroup = true;
+          }
+        }
+        else if (inGroup)
+        {
+          drawVerticals(g, sx, xwidth, visWidth, oldY, sy);
+          drawHorizontals(g, sx, xwidth, visWidth, top, bottom);
+
+          // reset top and bottom
+          top = -1;
+          bottom = -1;
+          inGroup = false;
+        }
+      }
+      if (inGroup)
+      {
+        sy = verticalOffset + ((i - startSeq) * charHeight);
+        drawVerticals(g, sx, xwidth, visWidth, oldY, sy);
+        drawHorizontals(g, sx, xwidth, visWidth, top, bottom);
+      }
+    }
+  }
+
+  /**
+   * Draw horizontal selection group boundaries at top and bottom positions
+   * 
+   * @param g
+   *          graphics object to draw on
+   * @param sx
+   *          start x position
+   * @param xwidth
+   *          width of gap
+   * @param visWidth
+   *          visWidth maximum available width
+   * @param top
+   *          position to draw top of group at
+   * @param bottom
+   *          position to draw bottom of group at
+   */
+  private void drawHorizontals(Graphics2D g, int sx, int xwidth,
+          int visWidth, int top, int bottom)
+  {
+    int width = xwidth;
+    int startx = sx;
+    if (startx < 0)
+    {
+      width += startx;
+      startx = 0;
+    }
 
+    // don't let width extend beyond current block, or group extent
+    // fixes JAL-2672
+    if (startx + width >= visWidth)
+    {
+      width = visWidth - startx;
+    }
+
+    if (top != -1)
+    {
+      g.drawLine(startx, top, startx + width, top);
     }
 
+    if (bottom != -1)
+    {
+      g.drawLine(startx, bottom - 1, startx + width, bottom - 1);
+    }
   }
 
   /**
+   * Draw vertical lines at sx and sx+xwidth providing they lie within
+   * [0,visWidth)
+   * 
+   * @param g
+   *          graphics object to draw on
+   * @param sx
+   *          start x position
+   * @param xwidth
+   *          width of gap
+   * @param visWidth
+   *          visWidth maximum available width
+   * @param oldY
+   *          top y value
+   * @param sy
+   *          bottom y value
+   */
+  private void drawVerticals(Graphics2D g, int sx, int xwidth, int visWidth,
+          int oldY, int sy)
+  {
+    // if start position is visible, draw vertical line to left of
+    // group
+    if (sx >= 0 && sx < visWidth)
+    {
+      g.drawLine(sx, oldY, sx, sy);
+    }
+
+    // if end position is visible, draw vertical line to right of
+    // group
+    if (sx + xwidth < visWidth)
+    {
+      g.drawLine(sx + xwidth, oldY, sx + xwidth, sy);
+    }
+  }
+  
+  /**
    * Highlights search results in the visible region by rendering as white text
    * on a black background. Any previous highlighting is removed. Answers true
    * if any highlight was left on the visible alignment (so status bar should be
@@ -1164,14 +1600,11 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       return false;
     }
     boolean wrapped = av.getWrapAlignment();
-
     try
     {
       fastPaint = !noFastPaint;
       fastpainting = fastPaint;
 
-      updateViewport();
-
       /*
        * to avoid redrawing the whole visible region, we instead
        * redraw just the minimal regions to remove previous highlights
@@ -1226,7 +1659,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   protected boolean drawMappedPositions(SearchResultsI results)
   {
-    if (results == null)
+    if ((results == null) || (gg == null)) // JAL-2784 check gg is not null
     {
       return false;
     }
@@ -1311,13 +1744,36 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   {
     String eventName = evt.getPropertyName();
 
+    if (eventName.equals(SequenceGroup.SEQ_GROUP_CHANGED))
+    {
+      fastPaint = true;
+      repaint();
+      return;
+    }
+    else if (eventName.equals(ViewportRanges.MOVE_VIEWPORT))
+    {
+      fastPaint = false;
+      repaint();
+      return;
+    }
+
     int scrollX = 0;
-    if (eventName.equals(ViewportRanges.STARTRES))
+    if (eventName.equals(ViewportRanges.STARTRES)
+            || eventName.equals(ViewportRanges.STARTRESANDSEQ))
     {
       // Make sure we're not trying to draw a panel
       // larger than the visible window
+      if (eventName.equals(ViewportRanges.STARTRES))
+      {
+        scrollX = (int) evt.getNewValue() - (int) evt.getOldValue();
+      }
+      else
+      {
+        scrollX = ((int[]) evt.getNewValue())[0]
+                - ((int[]) evt.getOldValue())[0];
+      }
       ViewportRanges vpRanges = av.getRanges();
-      scrollX = (int) evt.getNewValue() - (int) evt.getOldValue();
+
       int range = vpRanges.getEndRes() - vpRanges.getStartRes();
       if (scrollX > range)
       {
@@ -1328,7 +1784,6 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         scrollX = -range;
       }
     }
-
     // Both scrolling and resizing change viewport ranges: scrolling changes
     // both start and end points, but resize only changes end values.
     // Here we only want to fastpaint on a scroll, with resize using a normal
@@ -1336,7 +1791,22 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     // vertical start value.
     if (eventName.equals(ViewportRanges.STARTRES))
     {
-      // scroll - startres and endres both change
+      if (av.getWrapAlignment())
+        {
+          fastPaintWrapped(scrollX);
+        }
+        else
+        {
+          fastPaint(scrollX, 0);
+        }
+    }
+    else if (eventName.equals(ViewportRanges.STARTSEQ))
+    {
+      // scroll
+      fastPaint(0, (int) evt.getNewValue() - (int) evt.getOldValue());
+    }
+    else if (eventName.equals(ViewportRanges.STARTRESANDSEQ))
+    {
       if (av.getWrapAlignment())
       {
         fastPaintWrapped(scrollX);
@@ -1345,10 +1815,10 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       {
         fastPaint(scrollX, 0);
       }
-    }
-    else if (eventName.equals(ViewportRanges.STARTSEQ))
-    {
-      fastPaint(0, (int) evt.getNewValue() - (int) evt.getOldValue());
+      // bizarrely, we only need to scroll on the x value here as fastpaint
+      // copies the full height of the image anyway. Passing in the y value
+      // causes nasty repaint artefacts, which only disappear on a full
+      // repaint.
     }
   }
 
@@ -1365,7 +1835,9 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   {
     ViewportRanges ranges = av.getRanges();
 
-    if (Math.abs(scrollX) > ranges.getViewportWidth())
+    // if (Math.abs(scrollX) > ranges.getViewportWidth())
+    // JAL-2836, 2836 temporarily removed wrapped fastpaint for release 2.10.3
+    if (true)
     {
       /*
        * shift of more than one view width is 
@@ -1439,6 +1911,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
     ViewportRanges ranges = av.getRanges();
     int viewportWidth = ranges.getViewportWidth();
+    int charWidth = av.getCharWidth();
 
     /**
      * draw full height alignment in the second last row, last columns, if the
@@ -1450,7 +1923,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
     if (lastWidthPartHeight)
     {
-      int widthsAbove = visibleWidths - 2;
+      int widthsAbove = Math.max(0, visibleWidths - 2);
       int ypos = wrappedRepeatHeightPx * widthsAbove
               + wrappedSpaceAboveAlignment;
       int endRes = ranges.getEndRes();
@@ -1472,6 +1945,8 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     }
 
     /*
+     * draw newly visible columns in last wrapped width (none if we
+     * have reached the end of the alignment)
      * y-offset for drawing last width is height of widths above,
      * plus one gap row
      */
@@ -1480,7 +1955,6 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
             + wrappedSpaceAboveAlignment;
     int endRes = ranges.getEndRes();
     endRes += widthsAbove * viewportWidth;
-    endRes = Math.min(endRes, ranges.getVisibleAlignmentWidth());
     int startRes = endRes - columns + 1;
 
     /*
@@ -1497,7 +1971,10 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     gg.setFont(av.getFont());
     gg.setColor(Color.black);
 
-    drawWrappedWidth(gg, ypos, startRes, endRes, canvasHeight);
+    if (startRes < ranges.getVisibleAlignmentWidth())
+    {
+      drawWrappedWidth(gg, ypos, startRes, endRes, canvasHeight);
+    }
 
     /*
      * and finally, white fill any space below the visible alignment
@@ -1524,6 +2001,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     {
       return;
     }
+    int charWidth = av.getCharWidth();
 
     int canvasHeight = getHeight();
     ViewportRanges ranges = av.getRanges();
@@ -1596,6 +2074,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     }
   }
 
+  
   /**
    * Redraws any positions in the search results in the visible region of a
    * wrapped alignment. Any highlights are drawn depending on the search results
@@ -1608,15 +2087,17 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
    */
   protected boolean drawMappedPositionsWrapped(SearchResultsI results)
   {
-    if (results == null)
+    if ((results == null) || (gg == null)) // JAL-2784 check gg is not null
     {
       return false;
     }
-  
+    int charHeight = av.getCharHeight();
+
     boolean matchFound = false;
 
+    calculateWrappedGeometry(getWidth(), getHeight());
     int wrappedWidth = av.getWrappedWidth();
-    int wrappedHeight = getRepeatHeightWrapped();
+    int wrappedHeight = wrappedRepeatHeightPx;
 
     ViewportRanges ranges = av.getRanges();
     int canvasHeight = getHeight();
@@ -1715,23 +2196,12 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   }
 
   /**
-   * Answers the height in pixels of a repeating section of the wrapped
-   * alignment, including space above, scale above if shown, sequences, and
-   * annotation panel if shown
+   * Answers the width in pixels of the left scale labels (0 if not shown)
    * 
    * @return
    */
-  protected int getRepeatHeightWrapped()
+  int getLabelWidthWest()
   {
-    // gap (and maybe scale) above
-    int repeatHeight = charHeight * (av.getScaleAboveWrapped() ? 2 : 1);
-
-    // add sequences
-    repeatHeight += av.getRanges().getViewportHeight() * charHeight;
-
-    // add annotations panel height if shown
-    repeatHeight += getAnnotationHeight();
-
-    return repeatHeight;
+    return labelWidthWest;
   }
 }