问如何使用alpha掩码创建自定义NSCursor？

EN

static void maincustomcursor(bigmap *thedata, point hotspot)
{
    NSPoint thepoint;
    NSImage *newimage;
    NSCursor *thecursor;
    CGImageRef theimage;
    CGBitmapInfo theinfo;
    CGContextRef thecont;
    CGColorSpaceRef thecolor;
    int width, height, across;

    width = (*thedata).width;
    height = (*thedata).height;
    if (width != smalliconsize || height != smalliconsize) return;
    if (hotspot.h < 0) hotspot.h = 0;
    if (hotspot.h >= smalliconsize) hotspot.h = smalliconsize - 1;
    if (hotspot.v < 0) hotspot.v = 0;
    if (hotspot.v >= smalliconsize) hotspot.v = smalliconsize - 1;
    thepoint = NSMakePoint(hotspot.h, hotspot.v);
    across = (*thedata).rowbytes;
    thecolor = CGColorSpaceCreateDeviceRGB();
    theinfo = (CGBitmapInfo)kCGImageAlphaPremultipliedFirst;
    thecont = CGBitmapContextCreate((*thedata).baseaddr, width, height, 8, across, thecolor, theinfo);
    theimage = CGBitmapContextCreateImage(thecont);
    newimage = [[NSImage alloc] initWithCGImage:theimage size:NSZeroSize];
    thecursor = [[NSCursor alloc] initWithImage:newimage hotSpot:thepoint];
    [thecursor set];
    [thecursor release];
    [newimage release];
    CGImageRelease(theimage);
    CGContextRelease(thecont);
    CGColorSpaceRelease(thecolor);
}