From eb86f84d1835ee5be41ebfef365a9e11021c16c2 Mon Sep 17 00:00:00 2001
From: gmungoc <g.m.carstairs@dundee.ac.uk>
Date: Mon, 7 Aug 2017 16:04:38 +0200
Subject: [PATCH] JAL-2609 erase scale above before drawing scale/hidden
 markers

---
 src/jalview/gui/SeqCanvas.java |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index efc6910..7eb356b 100755
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -531,7 +531,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       start += wrappedWidthInResidues;
     }
 
-    drawWrappedDecorators(g, canvasHeight, startColumn);
+    drawWrappedDecorators(g, startColumn);
   }
 
   /**
@@ -673,15 +673,12 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
   /**
    * Draws scales left, right and above (if shown), and any hidden column
-   * markers, on the wrapped alignment
+   * markers, on all widths of the wrapped alignment
    * 
    * @param g
-   * @param ypos
    * @param startColumn
-   * @param endColumn
    */
-  protected void drawWrappedDecorators(Graphics g, int canvasHeight,
-          int startColumn)
+  protected void drawWrappedDecorators(Graphics g, int startColumn)
   {
     g.setFont(av.getFont());
     g.setColor(Color.black);
@@ -707,6 +704,15 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
 
       g.translate(labelWidthWest, 0);
 
+      /*
+       * white fill region of scale above and hidden column markers
+       * (to support incremental fast paint of image)
+       */
+      g.setColor(Color.white);
+      g.fillRect(0, ypos - wrappedSpaceAboveAlignment, viewportWidth
+              * charWidth, wrappedSpaceAboveAlignment);
+      g.setColor(Color.black);
+
       if (av.getScaleAboveWrapped())
       {
         drawNorthScale(g, startColumn, endColumn, ypos);
@@ -1406,7 +1412,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
       /*
        * draw all scales (if  shown) and hidden column markers
        */
-      drawWrappedDecorators(gg, getHeight(), ranges.getStartRes());
+      drawWrappedDecorators(gg, ranges.getStartRes());
 
       repaint();
     } finally
-- 
1.7.10.2