JAL-2556 Code tidy

diff --git a/src/jalview/gui/SeqCanvas.java b/src/jalview/gui/SeqCanvas.java
index 9d11976..3626383 100755 (executable)
--- a/src/jalview/gui/SeqCanvas.java
+++ b/src/jalview/gui/SeqCanvas.java
@@ -352,6 +352,8 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
   @Override
   public void paintComponent(Graphics g)
   {
+    super.paintComponent(g);
+
     updateViewport();
 
     // img is a cached version of the last view we drew
@@ -366,33 +368,13 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
     {
       return;
     }
-    BufferedImage lcimg = new BufferedImage(img.getWidth(), img.getHeight(),
-            img.getType());
-    Graphics2D g2d = lcimg.createGraphics();
-    g2d.drawImage(img, 0, 0, null);
-    g2d.dispose();
-
-
-    // BufferedImage lcimg = img; // take reference since other threads may null
-    // img and call later.
-    super.paintComponent(g);
 
     BufferedImage selectImage = drawSelectionGroup();
 
-    if (lcimg != null
-            && (fastPaint
-                    || (getVisibleRect().width != g.getClipBounds().width) || (getVisibleRect().height != g
-                    .getClipBounds().height)))
+    if (fastPaint || (getVisibleRect().width != g.getClipBounds().width)
+            || (getVisibleRect().height != g.getClipBounds().height))
     {
-      Graphics2D g2 = (Graphics2D) lcimg.getGraphics();
-
-      // overlay selection group on lcimg
-      if (selectImage != null)
-      {
-        g2.setComposite(
-                AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
-        g2.drawImage(selectImage, 0, 0, this);
-      }
+      BufferedImage lcimg = buildLocalImage(selectImage);
       g.drawImage(lcimg, 0, 0, this);
 
       fastPaint = false;
@@ -419,22 +401,32 @@ public class SeqCanvas extends JComponent implements ViewportListenerI
               ranges.getStartSeq(), ranges.getEndSeq(), 0);
     }
 
-    lcimg = new BufferedImage(img.getWidth(), img.getHeight(),
+    BufferedImage lcimg = buildLocalImage(selectImage);
+    g.drawImage(lcimg, 0, 0, this);
+  }
+
+  /*
+   * Make a local image by combining the cached image img
+   * with any selection
+   */
+  private BufferedImage buildLocalImage(BufferedImage selectImage)
+  {
+    // clone the cached image
+    BufferedImage lcimg = new BufferedImage(img.getWidth(), img.getHeight(),
             img.getType());
-    g2d = lcimg.createGraphics();
+    Graphics2D g2d = lcimg.createGraphics();
     g2d.drawImage(img, 0, 0, null);
-    g2d.dispose();
-
-    Graphics2D g2 = (Graphics2D) lcimg.getGraphics();
 
     // overlay selection group on lcimg
     if (selectImage != null)
     {
-      g2.setComposite(
+      g2d.setComposite(
               AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
-      g2.drawImage(selectImage, 0, 0, this);
+      g2d.drawImage(selectImage, 0, 0, this);
     }
-    g.drawImage(lcimg, 0, 0, this);
+    g2d.dispose();
+
+    return lcimg;
   }
 
   private void paintSeqGroup()