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Bug 369757 - [3.7.x] GLCanvas maintenance fix causes NullPointerException when changing parent on Mac
Summary: [3.7.x] GLCanvas maintenance fix causes NullPointerException when changing pa...
Status: RESOLVED FIXED
Alias: None
Product: Platform
Classification: Eclipse Project
Component: SWT (show other bugs)
Version: 4.2   Edit
Hardware: Macintosh Mac OS X - Carbon (unsup.)
: P3 critical (vote)
Target Milestone: 3.7.2   Edit
Assignee: Silenio Quarti CLA
QA Contact:
URL:
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Keywords:
Depends on:
Blocks:
 
Reported: 2012-01-25 18:15 EST by Steven Darnell CLA
Modified: 2012-01-26 11:14 EST (History)
3 users (show)

See Also:
john.arthorne: pmc_approved+
gheorghe: review+

Attachments
Modified code snippet to reproduce bug (contains JOGL dependency) (1.43 MB, application/octet-stream)
2012-01-25 18:24 EST, Steven Darnell CLA 		no flags Details
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Description Steven Darnell CLA 2012-01-25 18:15:44 EST 
Build Identifier: M20120118-0800

I use GLCanvas in my RCP app and a common workflow is to change the parent window of the widget (often moving a CTabFolder containing the GLCanvas from one partition to another). The app uses Eclipse SDK 3.7.0 and the correct behavior is observed. The workflow causes a NullPointerException when using a recent 3.7.x stream build (e.g. M20120118-0800).

I confirmed that you can successfully change the parent of a GLCanvas in SWT 3.7.0 and 3.7.1. The (soon to be) attached code snippet can be used to reproduce the error by changing the sample project's SWT dependency. I only tested the 32-bit version of SWT; I assume the same holds true for the 64-bit version.

I suspect this defect was introduced with the fix to Bug 343331, which was last changed 9/7/2011 (change previous to that in 2009).

I marked this bug CRITICAL as it introduces a crash condition in a maintenance release. I expect the same fix will be required in the 4.2/3.8 branch.

Reproducible: Always

Steps to Reproduce:
1. Create two shells (shell1, shell2)
2. Create a GLCanvas and set shell1 as parent
3. Change GLCanvas parent to shell2

Exception in thread "main" java.lang.NullPointerException
	at org.eclipse.swt.widgets.Canvas.viewWillMoveToWindow(Canvas.java:614)
	at org.eclipse.swt.widgets.Display.windowProc(Display.java:5683)
	at org.eclipse.swt.internal.cocoa.OS.objc_msgSend(Native Method)
	at org.eclipse.swt.internal.cocoa.NSView.addSubview(NSView.java:36)
	at org.eclipse.swt.widgets.Control.setParent(Control.java:3942)
	at steve.opengl.GLCanvasParentSwap.main(GLCanvasParentSwap.java:139)
Comment 1 Steven Darnell CLA 2012-01-25 18:24:06 EST 
Created attachment 210089 [details]
Modified code snippet to reproduce bug (contains JOGL dependency)

Snippet creates two shells and a GLCanvas, the changes the parent of the canvas from the first to the second shell. Comment in code indicates what triggers the exception.
Comment 2 Steven Darnell CLA 2012-01-25 18:31:21 EST 
@Silenio
I am CC'ing you because you were instrumental to the GLCanvas fast view fix on Mac (Bug 343331). I apologize if this is out of line.
Comment 4 Silenio Quarti CLA 2012-01-26 10:56:02 EST 
John/Bogdan, please could approve/review this patch for 3.7.2?

This is a regression in 3.7.2, it must be fixed.

The NullPointer happens because during the callback #viewWillMoveToWindow, NSView.window() returns null.  The fix is to use the window stored in the shell of the GLCanvas.