JAL-3502 improved fast paint of wrapped scales

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index 2832796..9689d5c 100755 (executable)
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -194,24 +194,34 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   void drawVerticalScale(Graphics g, final int startx, final int endx,
           final int ypos, final boolean left)
   {
-    int charHeight = av.getCharHeight();
-    int charWidth = av.getCharWidth();
+    final int charHeight = av.getCharHeight();
+    final int charWidth = av.getCharWidth();
 
-    int yPos = ypos + charHeight;
+    final int yPos = ypos + charHeight;
     int startX = startx;
     int endX = endx;
 
+    AlignmentI alignment = av.getAlignment();
     if (av.hasHiddenColumns())
     {
-      HiddenColumns hiddenColumns = av.getAlignment().getHiddenColumns();
+      HiddenColumns hiddenColumns = alignment.getHiddenColumns();
       startX = hiddenColumns.visibleToAbsoluteColumn(startx);
       endX = hiddenColumns.visibleToAbsoluteColumn(endx);
     }
     FontMetrics fm = getFontMetrics(av.getFont());
 
-    for (int i = 0; i < av.getAlignment().getHeight(); i++)
+    /*
+     * white fill the space for the scale for correct 'fast paint'
+     * (repainting only changed regions of the image)
+     * (fillRect origin is top left of rectangle)
+     */
+    g.setColor(Color.white);
+    g.fillRect(0, ypos, left ? labelWidthWest : labelWidthEast,
+            (alignment.getHeight() * charHeight));
+
+    for (int i = 0; i < alignment.getHeight(); i++)
     {
-      SequenceI seq = av.getAlignment().getSequenceAt(i);
+      SequenceI seq = alignment.getSequenceAt(i);
 
       /*
        * find sequence position of first non-gapped position -
@@ -236,15 +246,6 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         }
       }
 
-      /*
-       * white fill the space for the scale
-       */
-      g.setColor(Color.white);
-      int y = (yPos + (i * charHeight)) - (charHeight / 5);
-      // fillRect origin is top left of rectangle
-      g.fillRect(0, y - charHeight, left ? labelWidthWest : labelWidthEast,
-              charHeight + 1);
-
       if (value != -1)
       {
         /*
@@ -257,6 +258,7 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
         int labelLength = fm.stringWidth(valueAsString);
         int xOffset = labelSpace - labelLength;
         g.setColor(Color.black);
+        int y = (yPos + (i * charHeight)) - (charHeight / 5);
         g.drawString(valueAsString, xOffset, y);
       }
     }