Question

ok so im trying to make it so that when my app opens, the cursor changes, but to change it im putting an image overlay. So here is the code i have…

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
        // get the cursor image 
        NSPoint mouseLoc; 
        mouseLoc = [NSEvent mouseLocation]; //get cur

        NSLog(@"Mouse location is x=%d,y=%d",(int)mouseLoc.x,(int)mouseLoc.y);

        // get the mouse image 
        NSImage *overlay    =   [[[NSCursor arrowCursor] image] copy];

        NSLog(@"Mouse location is x=%d,y=%d cursor width = %d, cursor height = %d",(int)mouseLoc.x,(int)mouseLoc.y,(int)[overlay size].width,(int)[overlay size].height);

        int x = (int)mouseLoc.x;
        int y = (int)mouseLoc.y;
        int w = (int)[overlay size].width;
        int h = (int)[overlay size].height;
        int org_x = x;
        int org_y = y;

        size_t height = CGImageGetHeight([NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]);
        size_t width =  CGImageGetWidth([NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]);
        int bytesPerRow = CGImageGetBytesPerRow([NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]);

        unsigned int * imgData = (unsigned int*)malloc(height*bytesPerRow);

        // have the graphics context now, 
        CGRect bgBoundingBox = CGRectMake (0, 0, width,height);

        CGContextRef context =  CGBitmapContextCreate(imgData, width, 
                                                      height, 
                                                      8, // 8 bits per component 
                                                      bytesPerRow, 
                                                      CGImageGetColorSpace([NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]), 
                                                      CGImageGetBitmapInfo([NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]));

        // first draw the image 
        CGContextDrawImage(context,bgBoundingBox,[NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]);

        // then mouse cursor 
        CGContextDrawImage(context,CGRectMake(0, 0, width,height),[NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource:@"arrow" ofType:@"png"]]);

        // then mouse cursor 
        CGContextDrawImage(context,CGRectMake(org_x, org_y, w,h),[overlay CGImageForProposedRect: NULL context: NULL hints: NULL] );


        // assuming both the image has been drawn then create an Image Ref for that 

        CGImageRef pFinalImage = CGBitmapContextCreateImage(context);

        CGContextRelease(context);

        return pFinalImage; /* to be released by the caller */
    }

So ive tried this and it compiles with warnings regarding the url path but it has no errors. But when i open the app, it crashes! So can anyone help me out?

Answer 1

You’re taking an NSURL* and passing it to functions that take a CGImageRef. That isn’t even close to making sense, so I don’t know why you didn’t get errors. To load a CGImage from a URL, you need to use the CGImageSource functions like CGImageSourceCreateWithURL.

P.S., rather than just saying it crashes, run it under the debugger and find out exactly where it crashes.