X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;f=src%2Fjalview%2Fviewmodel%2FViewportRanges.java;h=104fb62be1541ddf9b41c35486a1311378d67628;hb=299d07a9554a3661d44395aa2c6bad9cecd10bf0;hp=6f817bb0cdd8c8a82a93a7b5c43da29686cfcc62;hpb=92c2fd083f7f5844693878f946441d75241f13bb;p=jalview.git

diff --git a/src/jalview/viewmodel/ViewportRanges.java b/src/jalview/viewmodel/ViewportRanges.java
index 6f817bb..104fb62 100644
--- a/src/jalview/viewmodel/ViewportRanges.java
+++ b/src/jalview/viewmodel/ViewportRanges.java
@@ -224,6 +224,7 @@ public class ViewportRanges extends ViewportProperties
    */
   public void setStartEndSeq(int start, int end)
   {
+    // System.out.println("ViewportRange setStartEndSeq " + start + " " + end);
     int[] oldvalues = updateStartEndSeq(start, end);
     int oldstartseq = oldvalues[0];
     int oldendseq = oldvalues[1];
@@ -285,12 +286,12 @@ public class ViewportRanges extends ViewportProperties
    * event.
    * 
    * @param seq
-   *          sequence position
+   *          sequence position in the range [0, height)
    */
   public void setEndSeq(int seq)
   {
-    int height = getViewportHeight();
-    setStartEndSeq(seq - height + 1, seq);
+    // BH 2018.04.18 added safety for seq < 0; comment about not being >= height
+    setStartEndSeq(Math.max(0, seq + 1 - getViewportHeight()), seq);
   }
 
   /**
@@ -425,17 +426,21 @@ public class ViewportRanges extends ViewportProperties
   public void setViewportStartAndHeight(int start, int h)
   {
     int vpstart = start;
+
+    int visHeight = getVisibleAlignmentHeight();
     if (vpstart < 0)
     {
       vpstart = 0;
     }
-    else if ((h <= getVisibleAlignmentHeight())
-            && (vpstart + h - 1 > getVisibleAlignmentHeight() - 1))
+    else if (h <= visHeight && vpstart + h > visHeight)
     // viewport height is less than the full alignment and we are running off
     // the bottom
     {
-      vpstart = getVisibleAlignmentHeight() - h;
+      vpstart = visHeight - h;
     }
+    // System.out.println("ViewportRanges setviewportStartAndHeight " + vpstart
+    // + " " + start + " " + h + " " + getVisibleAlignmentHeight());
+
     setStartEndSeq(vpstart, vpstart + h - 1);
   }
 
@@ -580,8 +585,8 @@ public class ViewportRanges extends ViewportProperties
     }
 
     int residuesToScroll = width * widthsToScroll;
-    int newStartRes = up ? oldStartRes - residuesToScroll : oldStartRes
-            + residuesToScroll;
+    int newStartRes = up ? oldStartRes - residuesToScroll
+            : oldStartRes + residuesToScroll;
     if (newStartRes < 0)
     {
       newStartRes = 0;
@@ -607,7 +612,7 @@ public class ViewportRanges extends ViewportProperties
     {
       scrollUp(false);
     }
-    
+
     HiddenColumns hidden = al.getHiddenColumns();
     while (x < hidden.visibleToAbsoluteColumn(startRes))
     {