UITextView freezes iPad app from textViewShouldBeginEditing. (Invalid Glyph Index)

Question

So I've been working on this bug for about a week now, and for the life of me I can't figure out what's happening.

Due to confidentiality issues I can't post too much code, but I'll do my best to explain everything.

What's happening is that we're populating a UITextField via code, and initially have the text greyed out. The user then can do one of two things:

1) Tap a button which says "commit" and a method is called which does the following method we'll call "commitData". It does the following:

1. Registers the commit with an undo Manager
2. Changes the text from grey to black
3. Register with our application that the text field has been updated and needs to be saved upon application close

2) Tap on the text field with the greyed out text, which then calls the following default apple method textViewShouldBeginEditing. From here we call our "commitData" method listed from option 1 like so:

-(BOOL)textViewShouldBeginEditing:(UITextView *)textView
{
    if ([[self box] hasGreyedOutText])
        [[self box] commitData];

    [self setActiveTextView:textView];
    return YES;
}

The issue we're having is that tapping the button to commit the greyed out text works perfectly fine, and we run into no issues.

HOWEVER

When we tap into the text field and trigger the textViewShouldBeginEditing method, our iPads can freeze up and make the user wait for a couple of minutes before finishing. When I mean freeze, I mean the entire iPad freezes. The iPad clock won't even update while this is happening.

When this happens, we get an error code in the console which says:

!!! _NSLayoutTreeLineFragmentRectForGlyphAtIndex invalid glyph index 2147483647

We can get the error code above to display from all of our hardware when following the steps above, but can only reproduce the freezing on an iPad 2(with 100% accuracy however).

• A note on this, my co-worker has found through diagnostics that we only have about 8MB of free RAM when this error occurs. We only ever hit this little of RAM on the iPad 2 however, so this could just be a coincidence.

I have a feeling that this could be related to threading and that we might need to somehow call our method after returning YES from the textViewShouldBeginEditing method, but I'm not quite sure how I should be going about that.

If anybody has any ideas on how to fix this, or even ideas that could point me in the right direction, I would be incredibly grateful. I've looked everywhere I can possibly think of, and none of the solutions I've found relating to the error code have ended up working.

Answer 1

I can't debug, so in my guess it may caused by non-main thread UI operation. So, my suggestion is to make sure your UI code is in mainThread. Try this:

-(BOOL)textViewShouldBeginEditing:(UITextView *)textView
{
    dispatch_async(dispatch_get_main_queue(), ^{ 
    if ([[self box] hasGreyedOutText])
        [[self box] commitData];
    [self setActiveTextView:textView];
    }
    return YES;
}