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Bug 300980

Summary:

[TextSizeDetermination] fails with disposed fonts

Product:

[RT] RAP

Reporter:

Benjamin Muskalla <b.muskalla>

Component:

RWT

Assignee:

Project Inbox <rap-inbox>

Status:

RESOLVED WONTFIX

QA Contact:

Severity:

normal

Priority:

Version:

1.3

Target Milestone:

---

Hardware:

All

OS:

All

Whiteboard:

Attachments:

Description	Flags
testcase	none
Another test case	none

Description Benjamin Muskalla

2010-01-27 07:59:34 EST

There are cases when we access fonts during the dispose phase of a widget. In case the font itself is disposed before (eg. listing to Display dispose event to dispose the resources) can cause exceptions as we try to access these disposed fonts.
Not yet sure how to handle this correctly but I think we should prevent accessing the text size determination during dispose.

Comment 1 Benjamin Muskalla

2010-01-27 08:00:08 EST

Created attachment 157388 [details]
testcase

Here is a testcase which shows the behavior for the Table widget.

Comment 2 Benjamin Muskalla

2010-01-27 11:02:26 EST

Another problem related to this is that Probes that are stored by the TSD can be disposed before the TSD kicks in.

Example:
    Display display = new Display();
    Shell shell = new Shell( display );
    shell.setLayout( new GridLayout( 1, false ) );
    Label label = new Label( shell, SWT.NONE );
    label.setText("sdjfdsjfh");
    final Font font = new Font(display, "foo", 10, SWT.BOLD);
    label.setFont( font );
    display.addListener( SWT.Dispose, new Listener() {
      public void handleEvent( Event event ) {
        font.dispose();
      }
    });
    shell.pack();
    shell.open();
    while( !shell.isDisposed() ) {
      if( !display.readAndDispatch() )
        display.sleep();
    }
    display.dispose();
    return 0;
    
    
Run the snippet and reload the page. The disposed font is still in the queue of the TSD but already disposed which leads to the following exception:

org.eclipse.swt.SWTException: Graphic is disposed
	at org.eclipse.swt.SWT.error(SWT.java:2757)
	at org.eclipse.swt.SWT.error(SWT.java:2677)
	at org.eclipse.swt.SWT.error(SWT.java:2648)
	at org.eclipse.swt.graphics.Font.getFontData(Font.java:168)
	at org.eclipse.swt.internal.graphics.TextSizeProbeStore.createProbeResult(TextSizeProbeStore.java:104)
	at org.eclipse.swt.internal.graphics.TextSizeDeterminationHandler.readProbedFonts(TextSizeDeterminationHandler.java:177)
	at org.eclipse.swt.internal.graphics.TextSizeDetermination.readStartupProbes(TextSizeDetermination.java:169)
	at org.eclipse.rwt.internal.lifecycle.RWTLifeCycle.createUI(RWTLifeCycle.java:252)
	at org.eclipse.rwt.internal.lifecycle.RWTLifeCycle$UIThreadController.run(RWTLifeCycle.java:117)
	at java.lang.Thread.run(Thread.java:619)
	at org.eclipse.rwt.internal.lifecycle.UIThread.run(UIThread.java:80)

Comment 3 Rüdiger Herrmann

2010-01-29 09:50:46 EST

Created attachment 157625 [details]
Another test case

Comment 4 Rüdiger Herrmann

2010-01-29 12:42:07 EST

The snippet from the description now works (with bug 301249 fixed)

Comment 5 Rüdiger Herrmann

2010-01-29 12:44:30 EST

Regarding the attached test case (Table_Test#testDisposedFont) I am not sure if this is a valid use case. Even though SWT seems to gracefully handle this situation, disposing of a font that is still in use looks more like a programming error to me.

Comment 6 Rüdiger Herrmann

2010-02-02 10:29:27 EST

After gathering some more feedback I will close this bug as WONTFIX. Even though SWT seems to handle disposed fonts somehow, it is certainly not considered a valid use case (for RWT at least)