Footer rendered at the bottom of the content view

[vilindberg]

Hi,

A few (too many unfortunately) of my users are experiencing an issue where the footer gets rendered at the bottom of the sheet content instead of the bottom of the sheet. I cannot reproduce it myself, so I wanted to ask if anyone else have experienced this themselves or got reports from their users about it so I can reproduce it before creating an issue.

This is basically how it looks:

The height for the footer is still reserved and the sheet has the correct height (we use fixed detent in this case and not auto) but the footer is rendered with its bottom at the bottom of the content view. The footer height is fixed height when opening the sheet and I have also tried passing that fixed height as footerProps and the issue is still there.

I use the latest version 3.10.0.

[lucaswickstrom]

It's a recycled-view race (on 3.10.0, and still present on main past v3.11.0-beta.7) in TrueSheetFooterView: updateLayoutMetrics can fire before the footer is reparented, so setupConstraintsWithHeight: early-returns (superview is nil) and the height is dropped. Then didMoveToSuperview falls back to self.frame.size.height, which on a recycled view is the stale frame from the previous present, so the footer ends up pinned to the bottom of the content instead of the sheet.

I can't reproduce it easily myself, but it shows up in our prod user reports and stopped after applying the patch below.

Fix: stash the height as _pendingHeight when superview is nil, and use it in didMoveToSuperview instead of the stale frame.

Full patch

diff --git a/ios/TrueSheetFooterView.mm b/ios/TrueSheetFooterView.mm
--- a/ios/TrueSheetFooterView.mm
+++ b/ios/TrueSheetFooterView.mm
@@ -21,6 +21,7 @@
 
 @implementation TrueSheetFooterView {
   CGFloat _lastHeight;
+  CGFloat _pendingHeight;
   BOOL _didInitialLayout;
   NSLayoutConstraint *_bottomConstraint;
   CGFloat _currentKeyboardOffset;
@@ -38,6 +39,7 @@
     self.backgroundColor = [UIColor clearColor];
 
     _lastHeight = 0;
+    _pendingHeight = 0;
     _didInitialLayout = NO;
     _bottomConstraint = nil;
     _currentKeyboardOffset = 0;
@@ -50,6 +52,11 @@
 - (void)setupConstraintsWithHeight:(CGFloat)height {
   UIView *parentView = self.superview;
   if (!parentView) {
+    // On recycled views, updateLayoutMetrics can fire before the view is
+    // reparented. Remember the desired height so didMoveToSuperview applies
+    // it instead of falling back to the stale self.frame from the previous
+    // present cycle.
+    _pendingHeight = height;
     return;
   }
 
@@ -70,13 +77,14 @@
   }
 
   _lastHeight = height;
+  _pendingHeight = 0;
 }
 
 - (void)didMoveToSuperview {
   [super didMoveToSuperview];
 
   if (self.superview) {
-    CGFloat initialHeight = self.frame.size.height;
+    CGFloat initialHeight = _pendingHeight > 0 ? _pendingHeight : self.frame.size.height;
     [self setupConstraintsWithHeight:initialHeight];
   }
 }
@@ -105,6 +113,7 @@
   }
 
   _lastHeight = 0;
+  _pendingHeight = 0;
   _didInitialLayout = NO;
   _bottomConstraint = nil;
   _currentKeyboardOffset = 0;

[lodev09]

Hey, do you mind creating PR? Thanks!

[lucaswickstrom]

Opened #688 with the fix.