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Bug 376478

Summary:	[GC] textExtent can cause SWTException with "graphic disposed" message
Product:	[RT] RAP	Reporter:	Victor Kirhenshtein <victor>
Component:	RWT	Assignee:	Project Inbox <rap.incubator-inbox>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	P3
Version:	1.4
Target Milestone:	1.5 M7
Hardware:	All
OS:	All
Whiteboard:

Description Victor Kirhenshtein

2012-04-11 07:19:53 EDT

Build Identifier: 1.5.0-M6-20120320-1638

TextUtilities.getTextExtents can cause SWTException with "graphic disposed" message if font passed to it is equal to previously passed font, but previous font already disposed. This is caused by FigureUtilities.getTextDimension method, which looks like this:

protected static org.eclipse.swt.graphics.Point getTextDimension(String s,
		Font f) {
	setFont(f);
	return getGC().textExtent(s);
}

setFont looks like this:

protected static void setFont(Font f) {
	if (appliedFont == f || f.equals(appliedFont))
		return;
	getGC().setFont(f);
	appliedFont = f;
	metrics = null;
}

because Font.equals does not count disposed field in comparison, setFont keeps disposed font for calculations, which later causes SWTException.

This can be easily fixed either by changing conditin in setFont to

if ((appliedFont == f || f.equals(appliedFont)) && !appliedFont.isDisposed())

or by changing Font.equals method to take disposed flag into consideration.




Reproducible: Always

Steps to Reproduce:
1. Create Font object (font1)
2. Call TextUtilities.getTextExtents with font1
3. Dispose font1
4. Create Font object font2 with same settings as font1
5. Call TextUtilities.getTextExtents with font2

Code sample:

	Font font1 = new Font(Display.getDefault(), "Verdana", 8, SWT.NORMAL);
	TextUtilities.INSTANCE.getTextExtents("aaa", font1);
	font1.dispose();
	Font font2 = new Font(Display.getDefault(), "Verdana", 8, SWT.NORMAL);
	TextUtilities.INSTANCE.getTextExtents("aaa", font2);  // will cause exception

Comment 1 Ivan Furnadjiev

2012-04-11 09:01:01 EDT

Actually, this is an RWT problem. Test case:
public void testSetFontOverEqualDisplosedFont() {
  Font font = new Font( display, "font-name", 11, SWT.NORMAL );
  gc.setFont( font );
  font.dispose();

  font = new Font( display, "font-name", 11, SWT.NORMAL );
  gc.setFont( font );

  assertSame( font, gc.getFont() );
}

Comment 2 Ivan Furnadjiev

2012-04-11 16:16:58 EDT

Fixed by moving the check for equal font to ControlGC to skip the GCOperation creation. Same applies to background and foreground colors. JUnit tests added.