From: gmungoc <g.m.carstairs@dundee.ac.uk>
Date: Tue, 27 Jun 2017 12:59:46 +0000 (+0100)
Subject: JAL-147 scroll wrapped panel by one width's worth at a time
X-Git-Tag: Release_2_10_3b1~187
X-Git-Url: http://source.jalview.org/gitweb/?a=commitdiff_plain;h=bf3206cc56a3bff812f96967a81cc9cff54a57b1;p=jalview.git

JAL-147 scroll wrapped panel by one width's worth at a time
---

diff --git a/src/jalview/gui/AlignmentPanel.java b/src/jalview/gui/AlignmentPanel.java
index 72b1cc9..3994c29 100644
--- a/src/jalview/gui/AlignmentPanel.java
+++ b/src/jalview/gui/AlignmentPanel.java
@@ -757,13 +757,19 @@ public class AlignmentPanel extends GAlignmentPanel implements
         // if we're scrolling to the position we're already at, stop
         // this prevents infinite recursion of events when the scroll/viewport
         // ranges values are the same
-        if ((offy * rowSize == oldX) && (oldwidth == rowSize))
+        int newX = offy * rowSize;
+        if ((newX == oldX) && (oldwidth == rowSize))
         {
           return;
         }
         else if (offy > -1)
         {
-          vpRanges.setViewportStartAndWidth(offy * rowSize, rowSize);
+          /*
+           * throttle to one width's worth at a time (so click in
+           * scrollbar doesn't jump over data)
+           */
+          newX = newX > oldX ? oldX + rowSize : oldX - rowSize;
+          vpRanges.setViewportStartAndWidth(newX, rowSize);
         }
       }
       else