Fix bottom commanding bug where dimming view is still accessible when…

… collapsed (#2072)

* Revert "Calculate Bottom Commanding header height instead of using constant (#2041)"

This reverts commit d298dac.

* change headerTopMargin

* set alpha explicitly if not transitioning

ios/FluentUI.Demo/FluentUI.Demo/Demos/BottomCommandingDemoController.swift

@@ -46,8 +46,7 @@ class BottomCommandingDemoController: DemoController {
 
     private lazy var heroItems: [CommandingItem] = {
         return Array(1...25).map {
-            let title = ($0 == 4) ? "Two line item" : "Item"
-            let item = CommandingItem(title: title + String($0), image: homeImage, action: commandAction)
+            let item = CommandingItem(title: "Item " + String($0), image: homeImage, action: commandAction)
             item.selectedImage = homeSelectedImage
             item.isOn = ($0 % 3 == 1)
             item.isEnabled = ($0 % 2 == 1)

ios/FluentUI/Bottom Commanding/BottomCommandingController.swift

@@ -402,6 +402,7 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
         headerView.addSubview(heroCommandStack)
 
         let sheetController = BottomSheetController(headerContentView: headerView, expandedContentView: makeSheetExpandedContent(with: tableView))
+        sheetController.headerContentHeight = Constants.BottomSheet.headerHeight
         sheetController.hostedScrollView = tableView
         sheetController.isHidden = isHidden
         sheetController.shouldAlwaysFillWidth = sheetShouldAlwaysFillWidth
@@ -533,7 +534,6 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
         } else {
             tableView.tableHeaderView = nil
         }
-        calculateHeaderHeight()
     }
 
     private func reloadHeroCommandOverflowStack() {
@@ -563,13 +563,6 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
         }
     }
 
-    @discardableResult
-    private func calculateHeaderHeight() -> CGFloat {
-        let headerHeight = heroCommandStack.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize).height + BottomSheetController.resizingHandleHeight
-        bottomSheetController?.headerContentHeight = headerHeight
-        return headerHeight
-    }
-
     private func updateAppearance() {
         guard isViewLoaded else {
             return
@@ -927,10 +920,10 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
         bottomSheetController.isExpandable = isExpandable
 
         let maxHeroItemHeight = heroCommandStack.arrangedSubviews.map { $0.intrinsicContentSize.height }.max() ?? Constants.defaultHeroButtonHeight
-        let headerHeightWithoutBottomWhitespace = BottomCommandingTokenSet.handleHeaderHeight + maxHeroItemHeight
+        let headerHeightWithoutBottomWhitespace = BottomCommandingTokenSet.headerTopMargin + maxHeroItemHeight
 
         // How much more whitespace is required at the bottom of the sheet header
-        let requiredBottomWhitespace = max(0, calculateHeaderHeight() - headerHeightWithoutBottomWhitespace)
+        let requiredBottomWhitespace = max(0, Constants.BottomSheet.headerHeight - headerHeightWithoutBottomWhitespace)
 
         // The safe area inset can fulfill some or all of our bottom whitespace requirement.
         // This is how much more we need, taking the inset into account.
@@ -940,7 +933,7 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
         let addedHeaderTopMargin = !isExpandable
             ? BottomSheetController.resizingHandleHeight
             : 0
-        bottomSheetHeroStackTopConstraint?.constant = BottomCommandingTokenSet.handleHeaderHeight + addedHeaderTopMargin
+        bottomSheetHeroStackTopConstraint?.constant = BottomCommandingTokenSet.headerTopMargin + addedHeaderTopMargin
 
         let oldCollapsedContentHeight = bottomSheetController.collapsedContentHeight
         let newCollapsedContentHeight = headerHeightWithoutBottomWhitespace + reducedBottomWhitespace + addedHeaderTopMargin
@@ -1125,6 +1118,10 @@ open class BottomCommandingController: UIViewController, TokenizedControlInterna
             static let moreButtonIcon: UIImage? = UIImage.staticImageNamed("more-24x24")
             static let moreButtonTitle: String = "CommandingBottomBar.More".localized
         }
+
+        struct BottomSheet {
+            static let headerHeight: CGFloat = 66
+        }
     }
 }
 

ios/FluentUI/Bottom Commanding/BottomCommandingTokenSet.swift

@@ -97,5 +97,5 @@ extension BottomCommandingTokenSet {
     static let tabVerticalPadding: CGFloat = GlobalTokens.spacing(.size80)
     static let tabHorizontalPadding: CGFloat = GlobalTokens.spacing(.size160)
     static let strokeWidth: CGFloat = GlobalTokens.stroke(.width05)
-    static let handleHeaderHeight: CGFloat = GlobalTokens.spacing(.size120)
+    static let headerTopMargin: CGFloat = GlobalTokens.spacing(.size60)
 }

ios/FluentUI/Bottom Sheet/BottomSheetController.swift

@@ -740,6 +740,15 @@ public class BottomSheetController: UIViewController, Shadowable, TokenizedContr
                 targetAlpha = abs(currentOffset - lowestUndimmedOffset) / (lowestUndimmedOffset - highestDimmedOffset)
             }
         }
+
+        if currentExpansionState != .transitioning {
+            // In the case that there has been a floating point precision error and
+            // targetAlpha is a value very close to 0 or 1, set it explicitly
+            if targetAlpha != 0 || targetAlpha != 1 {
+                targetAlpha = currentExpansionState == .expanded ? 1 : 0
+            }
+        }
+
         dimmingView.alpha = targetAlpha
     }
 
@@ -1051,6 +1060,9 @@ public class BottomSheetController: UIViewController, Shadowable, TokenizedContr
 
         bottomSheetView.isHidden = targetExpansionState == .hidden
 
+        updateDimmingViewAlpha()
+        updateDimmingViewAccessibility()
+
         // UIKit doesn't properly handle interrupted constraint animations, so we need to
         // detect and fix a possible desync here
         updateSheetLayoutGuideTopConstraint()