REFACTORING: Simplify DrawerConfiguration

Author: VilemKurz

Example/UIViewController-DisplayInDrawer/ContentViewController.swift

@@ -68,21 +68,21 @@ class ContentViewController: UIViewController {
 }
 
 extension ContentViewController: DrawerConfiguration {
-    func topPositionY(in parentFrame: CGRect) -> CGFloat {
+    func topPositionY(for parentHeight: CGFloat) -> CGFloat {
         guard isViewLoaded else { return 0 }
         /*
          You can return constant, but this is a more dynamic example:
          How to avoid making the drawer unneccessarily larger than its content
          */
         let minimalTopPosition: CGFloat = 50
-        let idealTopPosition = parentFrame.height - contentDerivedHeight()
+        let idealTopPosition = parentHeight - contentDerivedHeight()
         let result = fmax(minimalTopPosition, idealTopPosition)
         return result
     }
 
-    var bottomPositionHeight: CGFloat {
+    func bottomPositionY(for parentHeight: CGFloat) -> CGFloat {
         guard isViewLoaded else { return 0 }
-        return separatorView.frame.minY
+        return parentHeight - separatorView.frame.minY
     }
 
     func setPanGestureTarget(_ target: Any, action: Selector) {

UIViewController-DisplayInDrawer/Classes/PanGestureTarget.swift

@@ -24,8 +24,7 @@ final class PanGestureTarget {
     private weak var drawerConfiguration: DrawerConfiguration?
     private weak var drawerPositionDelegate: DrawerPositionDelegate?
     private var initialDrawerCenterLocation: CGPoint = .zero
-    private var bottomPositionHeight: CGFloat!
-    var basePositionY: CGFloat { return canvasView.frame.height - bottomPositionHeight }
+    var basePositionY: CGFloat!
     var topPositionY: CGFloat!
 
     init(canvasView: UIView,
@@ -42,8 +41,8 @@ final class PanGestureTarget {
     }
 
     internal func refreshDrawerPositions() {
-        bottomPositionHeight = drawerConfiguration?.bottomPositionHeight ?? 0
-        topPositionY = drawerConfiguration?.topPositionY(in: canvasView.bounds) ?? 0
+        basePositionY = drawerConfiguration?.bottomPositionY(for: canvasView.bounds.height) ?? 0
+        topPositionY = drawerConfiguration?.topPositionY(for: canvasView.bounds.height) ?? 0
     }
 
     deinit {
@@ -117,7 +116,7 @@ final class PanGestureTarget {
 
     private func isInUpperHalfOfMovement() -> Bool {
         let allowedMovementMinY = topPositionY!
-        let allowedMovementMaxY = basePositionY
+        let allowedMovementMaxY = basePositionY!
         let halfMovement = (allowedMovementMaxY - allowedMovementMinY) / 2
         let movementMidY = allowedMovementMinY + halfMovement
         return drawerContainerView.frame.minY < movementMidY

UIViewController-DisplayInDrawer/Classes/UIViewController+PresentDrawerController.swift

@@ -3,8 +3,8 @@
 import UIKit
 
 public protocol DrawerConfiguration: class {
-    func topPositionY(in parentFrame: CGRect) -> CGFloat
-    var bottomPositionHeight: CGFloat { get }
+    func topPositionY(for parentHeight: CGFloat) -> CGFloat
+    func bottomPositionY(for parentHeight: CGFloat) -> CGFloat
     /**
      drawerDismissClosure is injected by this lib.
      You should not change it, and you should call it when user presses dismiss button in your content view controller.
@@ -84,7 +84,7 @@ extension UIViewController {
         return { [weak self, weak containerView, weak initialDisplayAnimator] in
             guard let strongSelf = self, let strongContainerView = containerView else { return }
             let oldTopPositionY = panGestureTarget.topPositionY!
-            let oldBasePositionY = panGestureTarget.basePositionY
+            let oldBasePositionY = panGestureTarget.basePositionY!
             panGestureTarget.refreshDrawerPositions()
             let newContainerHeight = strongSelf.view.bounds.height - panGestureTarget.topPositionY + bottomOverpullPaddingHeight
             if strongContainerView.frame.height != newContainerHeight {
@@ -97,15 +97,18 @@ extension UIViewController {
             let newTopPositionIsDifferentThanOld = Int(panGestureTarget.topPositionY) != Int(oldTopPositionY)
             let isOnOldBottomPosition = Int(strongContainerView.frame.minY) == Int(oldBasePositionY)
             let newBottomPositionIsDifferentThanOld = Int(panGestureTarget.basePositionY) != Int(oldBasePositionY)
-            if isOnOldTopPosition && newTopPositionIsDifferentThanOld {
-                self?.updateWithNewYPosition(panGestureTarget.topPositionY,
-                                             containerView: strongContainerView,
-                                             inFlightAnimator: initialDisplayAnimator
+            let isInitialDisplayAnimation = initialDisplayAnimator != nil
+            if !isInitialDisplayAnimation && isOnOldTopPosition && newTopPositionIsDifferentThanOld {
+                self?.updateDrawerPosition(
+                    inFlightAnimator: initialDisplayAnimator,
+                    newTargetY: panGestureTarget.topPositionY,
+                    containerView: strongContainerView
                 )
             } else if isOnOldBottomPosition && newBottomPositionIsDifferentThanOld {
-                self?.updateWithNewYPosition(panGestureTarget.basePositionY,
-                                             containerView: strongContainerView,
-                                             inFlightAnimator: initialDisplayAnimator
+                self?.updateDrawerPosition(
+                    inFlightAnimator: initialDisplayAnimator,
+                    newTargetY: panGestureTarget.basePositionY,
+                    containerView: strongContainerView
                 )
             }
         }
@@ -122,10 +125,10 @@ extension UIViewController {
         controller.didMove(toParentViewController: self)
     }
 
-    private func updateWithNewYPosition(_ newY: CGFloat, containerView: UIView, inFlightAnimator: UIViewPropertyAnimator?) {
+    private func updateDrawerPosition(inFlightAnimator: UIViewPropertyAnimator?, newTargetY: CGFloat, containerView: UIView) {
         dLog("inFlightAnimator: \(String(describing: inFlightAnimator))")
         var newFrame = containerView.frame
-        newFrame.origin.y = newY
+        newFrame.origin.y = newTargetY
         if let animator = inFlightAnimator {
             animator.addAnimations { containerView.frame = newFrame }
         } else {
@@ -137,7 +140,7 @@ extension UIViewController {
                                             containerView: UIView,
                                             positionDelegate: DrawerPositionDelegate?) -> UIViewPropertyAnimator {
         var endFrame = containerView.frame
-        endFrame.origin.y = view.bounds.height - drawerConfiguration.bottomPositionHeight
+        endFrame.origin.y = drawerConfiguration.bottomPositionY(for: view.bounds.height)
         let animator = UIViewPropertyAnimator(duration: 0.25, curve: .easeInOut, animations: {
             containerView.frame = endFrame
         })
@@ -184,7 +187,7 @@ extension UIViewController {
 private extension UIView {
     func addContainerView(for drawerConfiguration: DrawerConfiguration, cornerRadius: CGFloat, bottomPaddingHeight: CGFloat) -> UIView {
         var startFrame = bounds
-        startFrame.size.height = bounds.height - drawerConfiguration.topPositionY(in: bounds) + bottomPaddingHeight
+        startFrame.size.height = bounds.height - drawerConfiguration.topPositionY(for: bounds.height) + bottomPaddingHeight
         startFrame.origin.y += bounds.height
         let containerView = UIView(frame: startFrame)
         containerView.preservesSuperviewLayoutMargins = true