NSView Subclass drawRect gets called in an infinite Loop

Question

I created a Subclass a of NSView to create a custom UI including a NSTextView. Therefore I use the drawRect Method to draw my UI. I also created a Subclass of NSImageView to get a mousedown Event. Whenever I click into my Subclassed NSImageView the drawRect Method of my View gets called in an infinite Loop and I can't figure out why. Building custom UIs is new for me so maybe I'm doing something essentially wrong?

TWIComposeFrameView.m:

#import "TWIComposeWindowFrameView.h"
#import "TWIImageView.h"

@implementation TWIComposeWindowFrameView

#pragma mark draw Rect of the View

//
// drawRect:
//
// Draws the frame of the window.
//
- (void)drawRect:(NSRect)rect
{
    //// Color Declarations
    NSColor* mainClrWhite = [NSColor colorWithCalibratedRed: 0.954 green: 0.954 blue:     0.954 alpha: 1];
    NSColor* transpGrey = [NSColor colorWithCalibratedRed: 0.224 green: 0.224 blue: 0.224 alpha: 0.745];
    NSColor* composeClrGrey = [NSColor colorWithCalibratedRed: 0.858 green: 0.842 blue: 0.842 alpha: 1];

    //// Abstracted Attributes
    NSRect composeRectRect = NSMakeRect(20, 70, 475, 210);
    NSRect attachmentRectRect = NSMakeRect(499, 195, 85, 85);


    //// transpRect Drawing
    NSBezierPath* transpRectPath = [NSBezierPath bezierPathWithRoundedRect: NSMakeRect(1, 0, 599, 299) xRadius: 10 yRadius: 10];
    [transpGrey setFill];
    [transpRectPath fill];


    //// mainRect Drawing
    NSBezierPath* mainRectPath = [NSBezierPath bezierPathWithRoundedRect: NSMakeRect(10, 10, 580, 280) xRadius: 10 yRadius: 10];
    [mainClrWhite setFill];
    [mainRectPath fill];


    //// composeRect Drawing
    NSBezierPath* composeRectPath = [NSBezierPath bezierPathWithRoundedRect: composeRectRect xRadius: 10 yRadius: 10];
    [composeClrGrey setFill];
    [composeRectPath fill];


    //// attachmentRect Drawing
    NSBezierPath* attachmentRectPath = [NSBezierPath bezierPathWithRoundedRect: attachmentRectRect xRadius: 10 yRadius: 10];
    [mainClrWhite setFill];
    [attachmentRectPath fill];
    [composeClrGrey setStroke];
    [attachmentRectPath setLineWidth: 1];
    [attachmentRectPath stroke];
}

- (id)initWithFrame:(NSRect)rect
{
    if (![super initWithFrame:rect])
        return nil;

    NSColor* composeClrGrey = [NSColor colorWithCalibratedRed: 0.858 green: 0.842 blue: 0.842 alpha: 1];
    NSRect composeRectRect = NSMakeRect(20, 70, 475, 210);
    NSRect attachmentRectRect = NSMakeRect(499, 195, 85, 85);
    //// Add Controls
    [self addComposeTextView:composeClrGrey composeRectRect:composeRectRect];
    [self addAttachmentImageView:attachmentRectRect];
    return self;
}

#pragma mark -
#pragma mark Add Controls to View

//
// Create and Add the Compose TextView
//
- (void)addComposeTextView:(NSColor *)composeClrGrey composeRectRect:(NSRect)composeRectRect
{
    NSTextView *composeTextView;
    if (composeTextView == nil)
    {
        composeTextView = [[NSTextView alloc] initWithFrame:composeRectRect];
        [composeTextView setBackgroundColor:composeClrGrey];
        [composeTextView setFont:[NSFont fontWithName:@"Helvetica" size:18]];
        [composeTextView setRichText:NO];
        [self addSubview:composeTextView];
    }
}

//
// Create and Add the Attachemant ImageView
//
- (void)addAttachmentImageView:(NSRect)attachmentRectRect
{
    NSImage *defaultImage = [NSImage imageNamed:@"168-upload-photo-2"];
    NSRect ivRect = NSMakeRect(attachmentRectRect.origin.x + 5, attachmentRectRect.origin.y + 5, attachmentRectRect.size.width - 10, attachmentRectRect.size.height - 10);
    TWIImageView *imageView = [[TWIImageView alloc] initWithFrame:ivRect];
    imageView.delegate = self;
    [imageView setEditable:YES];
    [self addSubview:imageView];
    [imageView setImage:defaultImage];
}

#pragma mark -
#pragma mark TWIImageView Delegate

//
// mouseDown Event on TWIImageView
//
- (void)myImageView:(TWIImageView *)view mouseDown:(NSEvent *)event
{
    NSLog(@"imageView clicked");
}
#pragma mark - 

@end

TWIImageView.h

@class TWIImageView;
@protocol TWIImageViewDelegate <NSObject>

- (void)myImageView:(TWIImageView *)view mouseDown:(NSEvent *)event;

@end

@interface TWIImageView : NSImageView
{

}

@property (assign) id<TWIImageViewDelegate> delegate;

@end

TWIImageView.m:

#import "TWIImageView.h"

@implementation TWIImageView

@synthesize delegate = _delegate;

- (void)mouseDown:(NSEvent *)event {
    if([self.delegate respondsToSelector:@selector(myImageView:mouseDown:)]) {
        [self.delegate myImageView:self mouseDown:event];
    }
}

@end

Is it wrong to create the controls in the overwritten initWithFrame Method? Or is my TWIImageView missing something important

StackTrace:

Thread 1, Queue : com.apple.main-thread
#0  0x0000000100001cd0 in -[TWIComposeWindowFrameView drawRect:] at     /Users/thomaswickl/Documents/Development/Git     Projects/QuickQuick/QuickQuick/TWIComposeWindowFrameView.m:24
#1  0x00007fff92efa170 in -[NSView _drawRect:clip:] ()
#2  0x00007fff92ef6fe3 in -[NSView  _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:topView: ] ()
#3  0x00007fff92ef7a74 in -[NSView _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:topView:] () 
#4  0x00007fff93045fdb in -[NSNextStepFrame _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:topView:] ()
#5  0x00007fff92ef1d9d in -[NSView _displayRectIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:] ()
#6  0x00007fff92ebbcc3 in -[NSView displayIfNeeded] ()
#7  0x00007fff93045e94 in -[NSNextStepFrame displayIfNeeded] ()
#8  0x00007fff92ebb1fc in _handleWindowNeedsDisplayOrLayoutOrUpdateConstraints ()
#9  0x00007fff934868f1 in __83-[NSWindow _postWindowNeedsDisplayOrLayoutOrUpdateConstraintsUnlessPostingDisabled]_block_invoke_01208 ()
#10 0x00007fff92b39417 in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ ()
#11 0x00007fff92b39381 in __CFRunLoopDoObservers ()
#12 0x00007fff92b147b8 in __CFRunLoopRun ()
#13 0x00007fff92b140e2 in CFRunLoopRunSpecific ()
#14 0x00007fff90ce8eb4 in RunCurrentEventLoopInMode ()
#15 0x00007fff90ce8b94 in ReceiveNextEventCommon ()
#16 0x00007fff90ce8ae3 in BlockUntilNextEventMatchingListInMode ()
#17 0x00007fff92eb8563 in _DPSNextEvent ()
#18 0x00007fff92eb7e22 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#19 0x00007fff92eaf1d3 in -[NSApplication run] ()
#20 0x00007fff92e53c06 in NSApplicationMain ()
#21 0x0000000100001242 in main at /Users/thomaswickl/Documents/Development/Git Projects/QuickQuick/QuickQuick/main.m:13
#22 0x00007fff955db7e1 in start ()

Frankly I do not see the loop. If there is one can't you just set a break point at the beginning of drawRect: and continue a couple of times and then look at the call stack which of the methods called actually invokes drawRect again and again? — Hermann Klecker
You might want to consider saving and restoring your graphics context during the -drawRect:. I don't know that it will solve your looping issue, but it will probably solve some problems down the road. — gaige
i can't see a looping issue in this code .I think its happening from somewhere else...just see if you are calling setNeedDisplay always (in a loop) !!! — arun.s
How I reproduce this is typing in the TxtView and then clicking on the ImageView. After a few clicks on the ImageView the drawRct Method gets called in a loop. I added the StackTrace but still don't get it. — user99070
It looks like saving and restoring the Graphics context did the Job! Thank you! — user99070

Hermann Klecker Hermann Klecker · Accepted Answer · 2013-03-18T15:12:25

I do not think that this answer will fix your issue. However, an init method may return a different object than self. So you better use this:

if (!(self = [super initWithFrame:rect]))
    return nil;

NSView Subclass drawRect gets called in an infinite Loop

2 Answers