Changeset 18388 in josm for trunk/src

Timestamp:

2022-03-08T15:52:28+01:00 (3 years ago)

Author:

taylor.smock

Message:

fix #21919: NPE in MapImage due to a race condition

This adds a synchronize block where disabledImgCache is calculated.
The new synchronize block will vie for the same lock as that in loadImage.
There should not be any significant UI penalty from this, as the loadImage
synchronized block does not depend upon anything particularly expensive, like
a network call. It also helps that almost all the time where both blocks will
be in contention, the new synchronize block will win.

File:

• trunk/src/org/openstreetmap/josm/gui/mappaint/styleelement/MapImage.java (modified) (1 diff)

trunk/src/org/openstreetmap/josm/gui/mappaint/styleelement/MapImage.java

@@ -140 +140 @@
         if (img == null)
             getImage(); // fix #7498 ?
-        Image disImg = GuiHelper.getDisabledImage(img);
-        if (disImg instanceof BufferedImage) {
-            disabledImgCache = (BufferedImage) disImg;
-        } else {
-            disabledImgCache = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
-            Graphics g = disabledImgCache.getGraphics();
-            g.drawImage(disImg, 0, 0, null);
-            g.dispose();
+        // This should fix #21919: NPE due to disabledImgCache being null (race condition with #loadImage())
+        synchronized (this) {
+            Image disImg = GuiHelper.getDisabledImage(img);
+            if (disImg instanceof BufferedImage) {
+                disabledImgCache = (BufferedImage) disImg;
+            } else {
+                disabledImgCache = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
+                Graphics g = disabledImgCache.getGraphics();
+                g.drawImage(disImg, 0, 0, null);
+                g.dispose();
+            }
         }
         return disabledImgCache;