Problem with NSImage in JNI

FROM : Daniel Dalquen
DATE : Tue Oct 30 22:49:48 2007

Hello everybody!

I have a problem with some code for a Java native interface that gets 
the icon for a specific file type from NSWorkspace and returns it to 
the calling Java method (see code below). Everything works fine on 
10.4, but on Leopard I get the following error message when the 
function is called and the Java app crashes:

"HIToolbox: ignoring exception 'Error (1002) creating CGSWindow' that 
raised inside Carbon event dispatch
java(1573,0xa0876074) malloc: *** error for object 0x21000: pointer 
being freed was not allocated"

I have found the statement that causes the crash, but don't really 
know what goes wrong (as I said, it works on Tiger). The Java app uses 
SWT for the GUI (which in turn uses Carbon afaik).

Any idea is appreciated :)

Cheers,
Daniel


JNIEXPORT jbyteArray JNICALL 
Java_com_wuala_platform_JNIWrapper_getIcon(JNIEnv *env, jclass cls, 
jstring arg, jint iconsize)
{
   // convert java string to UTF8 encoding
   const char *argutf  = (*env)->GetStringUTFChars(env, arg, JNI_FALSE);
   // create Cocoa string
   NSString * path = [NSString stringWithUTF8String:argutf];
   // ask the default workspace for the icon for the extension we want 
or a folder icon
   NSImage * iconimage;
   if ([path isEqualToString:@"/usr/"])
       iconimage = [[NSWorkspace sharedWorkspace] iconForFile:path];
   else
       iconimage = [[NSWorkspace sharedWorkspace] iconForFileType:path];
   // define and set the output size
   NSSize s = NSMakeSize(iconsize, iconsize);
   [iconimage setSize:s];
   // release the UTF8 string
   (*env)->ReleaseStringUTFChars(env, arg, argutf);
   // the icon that NSWorkspace returns is masked. In order for Java to 
be able to use it,
   // we must remove the transparency by compositing the icon onto a 
white background
   NSSize size = [iconimage size];
   NSImage *image2 = [[NSImage alloc] initWithSize:size];

   [image2 lockFocus]; //Crashes here in Leopard

   [[NSColor whiteColor] set];
   [NSBezierPath fillRect: NSMakeRect (0.0, 0.0, size.width, 
size.height)];
   [iconimage compositeToPoint:NSMakePoint(0.0, 0.0) 
operation:NSCompositeSourceOver fraction:1.0];
   [image2 unlockFocus];
   // get the TIFF data of the image
   NSData * imageData = [image2 TIFFRepresentation];
   unsigned length = [imageData length];
   // initialize a java byte array in which we will then copy the TIFF 
data
   jbyteArray result = 0;
   result = (*env)->NewByteArray(env,length);
   if (result != NULL) {
       (*env)->SetByteArrayRegion(env,result,0,length,(jbyte *)[imageData 
bytes]);
   }
   [image2 release];
   return result;
}