Safari-style bar behavior definer + delegate for creating a delegate chain

BLKFlexibleHeightBar/BLKFlexibleHeightBarBehaviorDefiner.h

@@ -20,6 +20,8 @@
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 @class BLKFlexibleHeightBar;
 
 /**
@@ -34,6 +36,11 @@
  */
 @property (nonatomic, readonly, weak) BLKFlexibleHeightBar *flexibleHeightBar;
 
+/**
+ All unhandled messages will be redirected to this delegate.
+ */
+@property (nonatomic, weak) id<NSObject> delegate;
+
 /**
  Determines whether snapping is enabled or not. Default value is YES.
  */
@@ -96,3 +103,5 @@
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView;
 
 @end
+
+NS_ASSUME_NONNULL_END

BLKFlexibleHeightBar/BLKFlexibleHeightBarBehaviorDefiner.m

@@ -108,7 +108,7 @@ - (void)snapWithScrollView:(UIScrollView *)scrollView
     {
         self.currentlySnapping = YES;
 
-        __block CGFloat snapPosition = MAXFLOAT;
+        __block CGFloat snapPosition = CGFLOAT_MAX;
         [self.snappingPositionsForProgressRanges enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
 
             NSValue *existingRangeValue = key;
@@ -124,7 +124,7 @@ - (void)snapWithScrollView:(UIScrollView *)scrollView
 
         }];
 
-        if(snapPosition != MAXFLOAT)
+        if(snapPosition != CGFLOAT_MAX)
         {
             [UIView animateWithDuration:0.15 animations:^{
 
@@ -149,6 +149,9 @@ - (void)snapWithScrollView:(UIScrollView *)scrollView
 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 {
     [self snapWithScrollView:scrollView];
+
+    NSInvocation* invocation = [self invocationForSelector:@selector(scrollViewDidEndDecelerating:) scrollView:scrollView];
+    [invocation invoke];
 }
 
 - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
@@ -157,11 +160,69 @@ - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL
     {
         [self snapWithScrollView:scrollView];
     }
+
+    NSInvocation* invocation = [self invocationForSelector:@selector(scrollViewDidEndDragging:willDecelerate:) scrollView:scrollView];
+    [invocation setArgument:&decelerate atIndex:3];
+    [invocation invoke];
 }
 
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
     scrollView.scrollIndicatorInsets =  UIEdgeInsetsMake(CGRectGetHeight(self.flexibleHeightBar.bounds), scrollView.scrollIndicatorInsets.left, scrollView.scrollIndicatorInsets.bottom, scrollView.scrollIndicatorInsets.right);
+
+    NSInvocation* invocation = [self invocationForSelector:@selector(scrollViewDidScroll:) scrollView:scrollView];
+    [invocation invoke];
+}
+
+# pragma mark - Message forwarding helper
+
+- (NSInvocation*)invocationForSelector:(SEL)selector scrollView:(UIScrollView*)scrollView
+{
+    if ([self.delegate respondsToSelector:selector])
+    {
+        NSMethodSignature* signature = [self.delegate.class instanceMethodSignatureForSelector:selector];
+        NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:signature];
+        [invocation setTarget:self.delegate];
+        [invocation setSelector:selector];
+        [invocation setArgument:&scrollView atIndex:2];
+
+        return invocation;
+    }
+
+    return nil;
+}
+
+# pragma mark - Message forwarding
+
+- (void)forwardInvocation:(NSInvocation*)anInvocation
+{
+    if ([self.delegate respondsToSelector:anInvocation.selector])
+    {
+        [anInvocation invokeWithTarget:self.delegate];
+    }
+}
+
+- (NSMethodSignature*)methodSignatureForSelector:(SEL)aSelector
+{
+    NSMethodSignature *first = [super methodSignatureForSelector:aSelector];
+    NSMethodSignature *second = [(NSObject*)self.delegate methodSignatureForSelector:aSelector];
+
+    if (first)
+    {
+        return first;
+    }
+    else if (second)
+    {
+        return second;
+    }
+
+    return nil;
+}
+
+- (BOOL)respondsToSelector:(SEL)aSelector
+{
+    BOOL result = [super respondsToSelector:aSelector] || [self.delegate respondsToSelector:aSelector];
+    return result;
 }
 
 @end

BLKFlexibleHeightBar/SafariStyleBehaviorDefiner.h

@@ -0,0 +1,34 @@
+/*
+ Copyright (c) 2015, Bryan Keller. All rights reserved.
+ Licensed under the MIT license <http://opensource.org/licenses/MIT>
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
+ documentation files (the "Software"), to deal in the Software without restriction, including without limitation
+ the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and
+ to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all copies or substantial portions
+ of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+ TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+ CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ IN THE SOFTWARE.
+ */
+
+/*
+ Safari style behavior definer by VragonerDev
+*/
+
+#import "BLKFlexibleHeightBarBehaviorDefiner.h"
+
+@interface SafariStyleBehaviorDefiner : BLKFlexibleHeightBarBehaviorDefiner
+
+/**
+ The non-negative value used for implementing Safari-style bar behavior when scrolling down with velocity.
+ Bigger value means that a bigger velocity is needed to expand the bar to the maximum height. The default value is 0.4.
+ */
+@property (nonatomic) CGFloat velocityThreshold;
+
+@end

BLKFlexibleHeightBar/SafariStyleBehaviorDefiner.m

@@ -0,0 +1,109 @@
+/*
+ Copyright (c) 2015, Bryan Keller. All rights reserved.
+ Licensed under the MIT license <http://opensource.org/licenses/MIT>
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
+ documentation files (the "Software"), to deal in the Software without restriction, including without limitation
+ the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and
+ to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all copies or substantial portions
+ of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+ TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+ CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ IN THE SOFTWARE.
+ */
+
+#import "SafariStyleBehaviorDefiner.h"
+#import "BLKFlexibleHeightBar.h"
+
+#define kDefaultVelocityThreshold   0.4
+
+@interface SafariStyleBehaviorDefiner ()
+{
+    CGFloat previousScrollPosition;
+}
+@end
+
+@implementation SafariStyleBehaviorDefiner
+
+#pragma mark -
+#pragma mark Init
+
+- (instancetype)init
+{
+    self = [super init];
+    if (self)
+    {
+        self.velocityThreshold = kDefaultVelocityThreshold;
+    }
+    return self;
+}
+
+#pragma mark -
+#pragma mark Scroll view delegate methods
+
+- (void)scrollViewWillBeginDragging:(UIScrollView*)scrollView
+{
+    [super scrollViewWillBeginDragging:scrollView];
+
+    previousScrollPosition = scrollView.contentOffset.y + scrollView.contentInset.top;
+}
+
+- (void)scrollViewDidScroll:(UIScrollView*)scrollView
+{
+    [super scrollViewDidScroll:scrollView];
+
+    CGFloat scrollPosition = scrollView.contentOffset.y + scrollView.contentInset.top;
+
+    if (!self.isCurrentlySnapping)
+    {
+        CGFloat newProgress = self.flexibleHeightBar.progress;
+
+        if (scrollPosition < 0.0)
+        {
+            newProgress = 0.0;
+        }
+        else if ((scrollView.contentOffset.y - scrollView.contentInset.bottom) >= scrollView.contentSize.height)
+        {
+            newProgress = 1.0;
+        }
+        else
+        {
+            CGFloat barHeight = self.flexibleHeightBar.maximumBarHeight - self.flexibleHeightBar.minimumBarHeight;
+            CGFloat progressDelta = (scrollPosition - previousScrollPosition) / barHeight;
+
+            if ((progressDelta > 0.0) || (scrollPosition < barHeight))
+            {
+                newProgress += progressDelta;
+            }
+        }
+
+        if (self.flexibleHeightBar.progress != newProgress)
+        {
+            self.flexibleHeightBar.progress = newProgress;
+            [self.flexibleHeightBar setNeedsLayout];
+        }
+    }
+
+    previousScrollPosition = scrollPosition;
+}
+
+- (void)scrollViewWillEndDragging:(UIScrollView*)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint*)targetContentOffset
+{
+    [super scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
+
+    if (velocity.y < -self.velocityThreshold)
+    {
+        self.flexibleHeightBar.progress = 0.0;
+
+        [self snapWithScrollView:scrollView];
+    }
+}
+
+@end
+
+#undef kDefaultVelocityThreshold