How can I detect if the iPhone my app is on, is going to use a simple transparent effect instead of the blur effect?

Question

My app on iPhone 4 running iOS 7 uses a UITabBar with a custom barTintColor. As mentioned in Apple documentation : https://developer.apple.com/library/ios/documentation/userexperience/conceptual/UIKitUICatalog/UITabBar.html

Tab bars are translucent by default on iOS 7. Additionally, there is a system blur applied to all tab bars. This allows your content to show through underneath the bar.

But this system blur is not visible on iPhone 4 and the UITabBar goes transparent on the device as shown below:

I believe that this might be happening because of the weaker GPU in iPhone 4 and thus it must be falling back to transparency instead of translucency. Reference : http://arstechnica.com/apple/2013/09/new-lease-on-life-or-death-sentence-ios-7-on-the-iphone-4/

A simple solution to this can be to conditionally make the UITabBar translucent for iPhone 4. But instead of putting this dependancy on the device type, I want to know if I can somehow detect if the iOS is going to be falling back to transparency when GPU is weak? (Thus making the condition more appropriate)

Answer 1

Here are some quick and dirty categories that detects if the device supports blur. Hope it solves your problem

@interface UIToolbar (support)
@property (nonatomic, readonly) BOOL supportsBlur;
@end

@implementation UIToolbar (support)
    -(BOOL) supportsBlur{
        return [self _supportsBlur:self];
    }


    -(BOOL)_supportsBlur:(UIView*) view{
        if ([view isKindOfClass:NSClassFromString(@"_UIBackdropEffectView")]){
            return YES;
        }

        for (UIView* subview in view.subviews){
            if ([self _supportsBlur:subview]){
                return YES;
            }
        }
        return NO;
    }
@end

// Use this category to detect if the device supports blur
@interface UIDevice (support)
@property (nonatomic, readonly) BOOL supportsBlur;
@end


@implementation UIDevice (support)
    -(BOOL) supportsBlur{
        static BOOL supportsBlur = NO;
        static dispatch_once_t onceToken = 0;
        dispatch_once(&onceToken, ^{
            UIToolbar* toolBar = [[UIToolbar alloc] init];
            [toolBar layoutSubviews];
            supportsBlur = toolBar.supportsBlur;
        });
        return supportsBlur;
    }
@end