From bc1d1b21389837bb9348e86000014f11e56bbbd3 Mon Sep 17 00:00:00 2001
From: Luke Zhao <me@lkzhao.com>
Date: Wed, 30 Oct 2024 15:14:02 -0700
Subject: [PATCH] add a content inset setter helper

---
 .../UIView+ComponentEngine.swift              | 30 ++++++++++++++++++-
 .../Extensions/UIScrollView+UIComponent.swift | 15 ++++------
 2 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/Sources/UIComponent/Core/ComponentView/UIView+ComponentEngine.swift b/Sources/UIComponent/Core/ComponentView/UIView+ComponentEngine.swift
index 36ddd579..d244d05e 100644
--- a/Sources/UIComponent/Core/ComponentView/UIView+ComponentEngine.swift
+++ b/Sources/UIComponent/Core/ComponentView/UIView+ComponentEngine.swift
@@ -19,6 +19,7 @@ extension UIView {
             _ = UIView.swizzle_layoutSubviews
             _ = UIView.swizzle_sizeThatFits
             _ = UIScrollView.swizzle_safeAreaInsetsDidChange
+            _ = UIScrollView.swizzle_setContentInset
             _componentEngine = componentEngine
             return componentEngine
         }
@@ -69,7 +70,7 @@ extension UIView {
     }
 
     static let swizzle_setBounds: Void = {
-        guard let originalMethod = class_getInstanceMethod(UIView.self, NSSelectorFromString("setBounds:")),
+        guard let originalMethod = class_getInstanceMethod(UIView.self, #selector(setter: bounds)),
               let swizzledMethod = class_getInstanceMethod(UIView.self, #selector(swizzled_setBounds(_:)))
         else { return }
         method_exchangeImplementations(originalMethod, swizzledMethod)
@@ -89,6 +90,13 @@ extension UIScrollView {
         method_exchangeImplementations(originalMethod, swizzledMethod)
     }()
 
+    static let swizzle_setContentInset: Void = {
+        guard let originalMethod = class_getInstanceMethod(UIScrollView.self, #selector(setter: contentInset)),
+              let swizzledMethod = class_getInstanceMethod(UIScrollView.self, #selector(swizzled_setContentInset(_:)))
+        else { return }
+        method_exchangeImplementations(originalMethod, swizzledMethod)
+    }()
+
     @objc func swizzled_safeAreaInsetsDidChange() {
         guard responds(to: #selector(swizzled_safeAreaInsetsDidChange)) else { return }
         swizzled_safeAreaInsetsDidChange()
@@ -96,5 +104,25 @@ extension UIScrollView {
             componentEngine.setNeedsReload()
         }
     }
+
+    @objc func swizzled_setContentInset(_ contentInset: UIEdgeInsets) {
+        // when contentOffset is at the top, and contentSize is set
+        // changing contentInset will not trigger a contentOffset change
+        // we manually adjust the contentOffset back to the top
+        // same for the horizontal axis
+        let yAtTop = contentOffset.y <= -adjustedContentInset.top
+        let xAtLeft = contentOffset.x <= -adjustedContentInset.left
+        swizzled_setContentInset(contentInset)
+        var newContentOffset = contentOffset
+        if yAtTop {
+            newContentOffset.y = -adjustedContentInset.top
+        }
+        if xAtLeft {
+            newContentOffset.x = -adjustedContentInset.left
+        }
+        if newContentOffset != contentOffset {
+            contentOffset = newContentOffset
+        }
+    }
 }
 
diff --git a/Sources/UIComponent/Extensions/UIScrollView+UIComponent.swift b/Sources/UIComponent/Extensions/UIScrollView+UIComponent.swift
index ca9a9759..4742a574 100644
--- a/Sources/UIComponent/Extensions/UIScrollView+UIComponent.swift
+++ b/Sources/UIComponent/Extensions/UIScrollView+UIComponent.swift
@@ -17,17 +17,12 @@ extension UIScrollView {
     }
 
     public var offsetFrame: CGRect {
-        let contentInset: UIEdgeInsets
-        if #available(iOS 11.0, *) {
-            contentInset = adjustedContentInset
-        } else {
-            contentInset = self.contentInset
-        }
+        let inset = adjustedContentInset
         return CGRect(
-            x: -contentInset.left,
-            y: -contentInset.top,
-            width: max(0, contentSize.width - bounds.width + contentInset.right + contentInset.left),
-            height: max(0, contentSize.height - bounds.height + contentInset.bottom + contentInset.top)
+            x: -inset.left,
+            y: -inset.top,
+            width: max(0, contentSize.width - bounds.width + inset.right + inset.left),
+            height: max(0, contentSize.height - bounds.height + inset.bottom + inset.top)
         )
     }