Re: Graphos: works on Cocoa not on GNUstep

[Fred Kiefer]

On 12.09.2012 22:09, Wolfgang Lux wrote:
> Hi Riccardo,
>
> > > This code works on OS X either because Cocoa is returning a
> > > preallocated color (you might try whether copying a text object
> > > with some non-standard color works) or because Cocoa uses a cache
> > > of color objects.
> > On my version, I did not get a crash for both "standard" as
> > randomly choosen colors of the color wheel. For you it crashed
> > though. I just ocmmited the fix, does it work for you on Mac now?
>
> the fix works, but I now get a different crash whenever the mouse
> moves over the document window.
>
> Thread 0 Crashed:  Dispatch queue: com.apple.main-thread 0
> libobjc-gnu.3.dylib             0x0000000100d0cbad objc_msg_lookup +
> 45 1   libgnustep-gui.0.23.dylib        0x00000001002625c5 -[NSWindow
> _checkTrackingRectangles:forEvent:] + 647 (NSWindow.m:3714) 2
> libgnustep-gui.0.23.dylib       0x0000000100262aa2 -[NSWindow
> _checkTrackingRectangles:forEvent:] + 1892 (NSWindow.m:3784) 3
> libgnustep-gui.0.23.dylib       0x0000000100262aa2 -[NSWindow
> _checkTrackingRectangles:forEvent:] + 1892 (NSWindow.m:3784) 4
> libgnustep-gui.0.23.dylib       0x0000000100262aa2 -[NSWindow
> _checkTrackingRectangles:forEvent:] + 1892 (NSWindow.m:3784) 5
> libgnustep-gui.0.23.dylib       0x0000000100262aa2 -[NSWindow
> _checkTrackingRectangles:forEvent:] + 1892 (NSWindow.m:3784) 6
> libgnustep-gui.0.23.dylib       0x0000000100264214 -[NSWindow
> sendEvent:] + 4023 (NSWindow.m:4136) 7   libgnustep-gui.0.23.dylib
> 0x0000000100089d1d -[NSApplication sendEvent:] + 755
> (NSApplication.m:2239) 8   libgnustep-gui.0.23.dylib
> 0x0000000100088775 -[NSApplication run] + 632 (NSApplication.m:1617)
> 9   libgnustep-gui.0.23.dylib           0x0000000100066743
> NSApplicationMain + 638 (Functions.m:93) 10  Graphos
> 0x000000010002aaba main + 32 (main.m:14) 11  Graphos
> 0x00000001000010a4 start + 52
>
> After a bit of debugging, I tracked this down to the initializer of
> GRDocView, which contains this code: NSImage *img; NSCursor *cur;
>
> img = [NSImage imageNamed: @"blackarrow.tiff"]; cur = [[NSCursor
> alloc] initWithImage: img hotSpot: NSMakePoint(0, 0)]; [cur
> setOnMouseEntered: YES]; [cur setOnMouseExited: YES]; [self
> addTrackingRect: [self frame] owner: cur userData: NULL assumeInside:
> YES]; [cur release]; Here you create a fresh cursor, then add a
> tracking rectangle to the view with the cursor as the owner of the
> tracing rectangle, and finally release the cursor. This leaves a
> dangling pointer to the cursor behind, which crashes the application
> when the tracking areas of the window containing the new GRDocView
> are examined. I am not sure whether this is supposed to work under
> Cocoa (the documentation remains silent on whether the owner of a
> tracking rectangle is retained), but in any case it would be more
> safe to retain the cursor in an attribute of the GRDoc view and
> release it when the view is deallocated.

Wolfgang is correct here. In GNUstep we don't retain the owner of the
tracking record, but do so for the cursor, when addCursorRect:... is
used. Maybe you should just switch to that method? See:

http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/EventOverview/MouseTrackingEvents/MouseTrackingEvents.html