From 05ba3a256597a3de3090431cb00bbefc4e4e5dcf Mon Sep 17 00:00:00 2001
From: Dustin Shahidehpour <dust@instagram.com>
Date: Fri, 14 Oct 2016 14:22:49 -0700
Subject: [PATCH] Do not measure the view if it is hidden.

Summary: If views are hidden on screen, we don't want to bother including them in layout calculations.

Reviewed By: rnystrom

Differential Revision: D4022992

fbshipit-source-id: 2e93eb911f26223f305ef7ce788f86d050b83e4a
---
 uikit/CSSLayout/Tests/CSSLayoutTests.m | 17 +++++++++++++++--
 uikit/CSSLayout/UIView+CSSLayout.m     |  8 ++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/uikit/CSSLayout/Tests/CSSLayoutTests.m b/uikit/CSSLayout/Tests/CSSLayoutTests.m
index 08a71416..cd550bb3 100644
--- a/uikit/CSSLayout/Tests/CSSLayoutTests.m
+++ b/uikit/CSSLayout/Tests/CSSLayoutTests.m
@@ -16,11 +16,24 @@
 
 @implementation CSSLayoutTests
 
-- (void)testSmoke
+- (void)testHiddenViewsAreNotMeasured
 {
+  const CGSize firstSize = CGSizeMake(100, 100);
   UIView *view = [[UIView alloc] initWithFrame:CGRectZero];
   [view css_setUsesFlexbox:YES];
-  XCTAssertTrue([view css_usesFlexbox]);
+  [view css_setWidth:firstSize.width];
+  [view css_setHeight:firstSize.height];
+
+  [view css_applyLayout];
+  XCTAssertTrue(CGSizeEqualToSize(firstSize, view.frame.size));
+
+  const CGSize newSize = CGSizeMake(200, 200);
+  [view css_setWidth:newSize.width];
+  [view css_setHeight:newSize.height];
+  view.hidden = YES;
+
+  [view css_applyLayout];
+  XCTAssertFalse(CGSizeEqualToSize(newSize, view.frame.size));
 }
 
 @end
diff --git a/uikit/CSSLayout/UIView+CSSLayout.m b/uikit/CSSLayout/UIView+CSSLayout.m
index 194e08ca..8fc582c5 100644
--- a/uikit/CSSLayout/UIView+CSSLayout.m
+++ b/uikit/CSSLayout/UIView+CSSLayout.m
@@ -226,6 +226,10 @@ static void _updateFrameRecursive(UIView *view);
 @end
 
 static void _attachNodesRecursive(UIView *view) {
+  if (view.isHidden) {
+    return;
+  }
+
   CSSNodeRef node = [view cssNode];
   const BOOL usesFlexbox = [view css_usesFlexbox];
   const BOOL isLeaf = !usesFlexbox || view.subviews.count == 0;
@@ -258,6 +262,10 @@ static void _attachNodesRecursive(UIView *view) {
 }
 
 static void _updateFrameRecursive(UIView *view) {
+  if (view.isHidden) {
+    return;
+  }
+
   CSSNodeRef node = [view cssNode];
   const BOOL usesFlexbox = [view css_usesFlexbox];
   const BOOL isLeaf = !usesFlexbox || view.subviews.count == 0;