From: gmungoc <g.m.carstairs@dundee.ac.uk>
Date: Tue, 18 Jul 2017 13:44:27 +0000 (+0100)
Subject: JAL-147 don't scroll up beyond startRes = 0
X-Git-Tag: Release_2_10_3b1~132^2~39
X-Git-Url: http://source.jalview.org/gitweb/?a=commitdiff_plain;h=ddbcb3e33e1a8d4c644472cfa3d28b193da97064;p=jalview.git

JAL-147 don't scroll up beyond startRes = 0
---

diff --git a/src/jalview/appletgui/AlignmentPanel.java b/src/jalview/appletgui/AlignmentPanel.java
index f8f31b2..4147177 100644
--- a/src/jalview/appletgui/AlignmentPanel.java
+++ b/src/jalview/appletgui/AlignmentPanel.java
@@ -817,14 +817,14 @@ public class AlignmentPanel extends Panel implements AdjustmentListener,
       {
         return;
       }
-      else if (newY > -1)
+      if (newY > -1)
       {
         /*
          * limit page up/down to one width's worth of positions
          */
         int rowSize = vpRanges.getViewportWidth();
         int newX = newY > oldY ? oldX + rowSize : oldX - rowSize;
-        vpRanges.setViewportStartAndWidth(newX, rowSize);
+        vpRanges.setViewportStartAndWidth(Math.max(0, newX), rowSize);
       }
     }
     else
diff --git a/src/jalview/gui/AlignmentPanel.java b/src/jalview/gui/AlignmentPanel.java
index a732527..e62707f 100644
--- a/src/jalview/gui/AlignmentPanel.java
+++ b/src/jalview/gui/AlignmentPanel.java
@@ -809,14 +809,14 @@ public class AlignmentPanel extends GAlignmentPanel implements
       {
         return;
       }
-      else if (newY > -1)
+      if (newY > -1)
       {
         /*
          * limit page up/down to one width's worth of positions
          */
         int rowSize = vpRanges.getViewportWidth();
         int newX = newY > oldY ? oldX + rowSize : oldX - rowSize;
-        vpRanges.setViewportStartAndWidth(newX, rowSize);
+        vpRanges.setViewportStartAndWidth(Math.max(0, newX), rowSize);
       }
     }
     else