In current trunk build, I'm not able to pinch zoom on mobile wikipedia, using the HTC Desire HD. It works fine in Aurora and beta. It also works fine on trunk on the Galaxy SII and Galaxy Nexus. I've attached a catlog, while trying to pinch zoom, relevant part: 06-20 11:03:08.884: W/System.err(11955): java.lang.NullPointerException 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.ScreenshotHandler$RepaintRunnable.addRectToRepaint(GeckoAppShell.java:2178) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.ScreenshotHandler.notifyPaintedRect(GeckoAppShell.java:2191) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.GeckoAppShell.notifyPaintedRect(GeckoAppShell.java:2115) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.GeckoAppShell.nativeRun(Native Method) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.GeckoAppShell.nativeRun(Native Method) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.GeckoAppShell.nativeRun(Native Method) 06-20 11:03:08.884: W/System.err(11955): at org.mozilla.gecko.GeckoAppShell.runGecko(GeckoAppShell.java:474)

I guess this could be a regression of bug 755070, somehow?

Looking at the code I think this could happen if the MozAfterPaint listener triggers before the handleDocumentStop code on the very first page, because then addRectToRepaint will get called before sCheckerboardPageRect has been initialized.

Although now that I see the bug title, the pinch zooming is completely unrelated to the NPE in ScreenshotHandler. Let's use this bug to track the NPE and open another one for the pinch zooming.