JAL-1722 fix: don’t draw visible regions outside viewport view

diff --git a/src/jalview/appletgui/SeqCanvas.java b/src/jalview/appletgui/SeqCanvas.java
index ce70597..024fdc7 100755 (executable)
--- a/src/jalview/appletgui/SeqCanvas.java
+++ b/src/jalview/appletgui/SeqCanvas.java
@@ -276,6 +276,7 @@ public class SeqCanvas extends Panel
    * at 0). NOTE 1: The av limits are set in setFont in this class and in the
    * adjustment listener in SeqPanel when the scrollbars move.
    */
+  @Override
   public void update(Graphics g)
   {
     paint(g);
@@ -573,10 +574,17 @@ public class SeqCanvas extends Panel
           g1.translate(-screenY * avcharWidth, 0);
           screenY += blockEnd - blockStart + 1;
           blockStart = hideEnd + 1;
+
+          if (screenY > (endRes - startRes))
+          {
+            // already rendered last block
+            return;
+          }
         }
       }
       if (screenY <= (endRes - startRes))
       {
+        // remaining visible region to render
         blockEnd = blockStart + (endRes - startRes) - screenY;
         g1.translate(screenY * avcharWidth, 0);
         draw(g1, blockStart, blockEnd, startSeq, endSeq, offset);

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index 5706fe7..0f24b4b 100755 (executable)
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -335,6 +335,7 @@ public class SeqCanvas extends JComponent
    */
 
   // Set this to false to force a full panel paint
+  @Override
   public void paintComponent(Graphics g)
   {
     updateViewport();
@@ -682,10 +683,17 @@ public class SeqCanvas extends JComponent
         g1.translate(-screenY * charWidth, 0);
         screenY += blockEnd - blockStart + 1;
         blockStart = hideEnd + 1;
+
+        if (screenY > (endRes - startRes))
+        {
+          // already rendered last block
+          return;
+        }
       }
 
       if (screenY <= (endRes - startRes))
       {
+        // remaining visible region to render
         blockEnd = blockStart + (endRes - startRes) - screenY;
         g1.translate(screenY * charWidth, 0);
         draw(g1, blockStart, blockEnd, startSeq, endSeq, offset);