X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;ds=inline;f=src%2Fjalview%2Fgui%2FSeqCanvas.java;h=c243a2e02fbf34f52a0fa167ec6ee29190189a93;hb=8548008f4fbd321b445c7e69fbdffda26e21f457;hp=698489e717589fb504aceb3f31b092f2707d443a;hpb=9218eaf932c0847b83e9886f5c06d70a0bc7808e;p=jalview.git

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index 698489e..c243a2e 100755
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -115,7 +115,7 @@ public class SeqCanvas extends JPanel
 
 public void fastPaint(int horizontal, int vertical)
 {
-    if (horizontal == 0 && vertical == 0)
+    if (horizontal == 0 && vertical == 0 || gg==null)
       return;
 
     gg.copyArea(0, 0, imgWidth, imgHeight, -horizontal * av.charWidth,
@@ -133,11 +133,19 @@ public void fastPaint(int horizontal, int vertical)
 
     else if (vertical > 0) // scroll down
     {
-      transY = imgHeight - vertical * av.charHeight;
       ss = es - vertical;
+      if(ss<av.startSeq) // ie scrolling too fast, more than a page at a time
+        ss = av.startSeq;
+      else
+        transY = imgHeight - vertical * av.charHeight;
     }
     else if (vertical < 0)
+    {
       es = ss - vertical;
+      if(es > av.endSeq)
+        es = av.endSeq;
+    }
+
 
     gg.translate(transX, transY);