[MediaWiki-commits] [Gerrit] Save scroll position across rotation better - change (apps...wikipedia)

[Brion VIBBER (Code Review)]

Brion VIBBER has uploaded a new change for review.

  https://gerrit.wikimedia.org/r/150740

Change subject: Save scroll position across rotation better
......................................................................

Save scroll position across rotation better

When rotating, we now check for the element that's at the top of the
screen, estimate how far into it we were (by percentage of height),
and return us to the recalculated position after rotating.

Bug: 68683
Change-Id: Ibdd0f59bde682da46040fa3b0a5b8daab4822721
---
M wikipedia/View Controllers/WebView/WebViewController.m
1 file changed, 39 insertions(+), 20 deletions(-)


  git pull ssh://gerrit.wikimedia.org:29418/apps/ios/wikipedia 
refs/changes/40/150740/1

diff --git a/wikipedia/View Controllers/WebView/WebViewController.m 
b/wikipedia/View Controllers/WebView/WebViewController.m
index 1ab10f4..bd48251 100644
--- a/wikipedia/View Controllers/WebView/WebViewController.m
+++ b/wikipedia/View Controllers/WebView/WebViewController.m
@@ -72,7 +72,7 @@
 
 @property (nonatomic) BOOL unsafeToScroll;
 
-@property (nonatomic) NSInteger indexOfFirstOnscreenSectionBeforeRotate;
+@property (nonatomic) float relativeScrollOffsetBeforeRotate;
 @property (nonatomic) NSUInteger sectionToEditId;
 
 @property (strong, nonatomic) NSDictionary *adjacentHistoryIDs;
@@ -142,8 +142,6 @@
     self.zeroStatusLabel.text = @"";
     
     self.sectionToEditId = 0;
-
-    self.indexOfFirstOnscreenSectionBeforeRotate = -1;
 
     [[NSNotificationCenter defaultCenter] addObserver: self
                                              selector: 
@selector(webViewFinishedLoading)
@@ -710,6 +708,15 @@
 
     point.y += 2;
     
+    [self tocScrollWebViewToPoint:point
+                         duration:duration
+                      thenHideTOC:hideTOC];
+}
+
+-(void)tocScrollWebViewToPoint: (CGPoint)point
+                      duration: (CGFloat)duration
+                   thenHideTOC: (BOOL)hideTOC
+{
     [UIView animateWithDuration: duration
                           delay: 0.0f
                         options: UIViewAnimationOptionBeginFromCurrentState
@@ -1763,14 +1770,17 @@
 
 
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
 duration:(NSTimeInterval)duration
 {
-    NSManagedObjectID *articleID = [articleDataContext_.mainContext 
getArticleIDForTitle: [SessionSingleton sharedInstance].currentArticleTitle
-                                                                               
   domain: [SessionSingleton sharedInstance].currentArticleDomain];
-    if (articleID) {
-        Article *article = (Article *)[articleDataContext_.mainContext 
objectWithID:articleID];
-
-        self.indexOfFirstOnscreenSectionBeforeRotate = [self.webView 
getIndexOfTopOnScreenElementWithPrefix:@"section_heading_and_content_block_" 
count:article.section.count];
-    }
-    //self.view.alpha = 0.0f;
+    NSString *js = @"(function() {"
+                   @"    _topElement = document.elementFromPoint( 
window.innerWidth / 2, 0 );"
+                   @"    if (_topElement) {"
+                   @"        var rect = _topElement.getBoundingClientRect();"
+                   @"        return rect.top / rect.height;"
+                   @"    } else {"
+                   @"        return 0;"
+                   @"    }"
+                   @"})()";
+    float relativeScrollOffset = [[self.webView 
stringByEvaluatingJavaScriptFromString:js] floatValue];
+    self.relativeScrollOffsetBeforeRotate = relativeScrollOffset;
 
     [self tocHideWithDuration:@0.0f];
     
@@ -1781,20 +1791,29 @@
 {
     [super didRotateFromInterfaceOrientation:fromInterfaceOrientation];
 
-    [self 
performSelector:@selector(scrollToIndexOfFirstOnscreenSectionBeforeRotate) 
withObject:nil afterDelay:0.1f];
+    [self scrollToElementOnScreenBeforeRotate];
     
     [self updateWebViewContentAndScrollInsets];
 }
 
--(void)scrollToIndexOfFirstOnscreenSectionBeforeRotate{
-    if(self.indexOfFirstOnscreenSectionBeforeRotate == -1)return;
-    NSString *elementId = [NSString 
stringWithFormat:@"section_heading_and_content_block_%ld", 
(long)self.indexOfFirstOnscreenSectionBeforeRotate];
-    
-    [self tocScrollWebViewToSectionWithElementId: elementId
-                                        duration: 0.2
-                                     thenHideTOC: NO];
+-(void)scrollToElementOnScreenBeforeRotate
+{
+    NSString *js = @"(function() {"
+                   @"    if (_topElement) {"
+                   @"        var rect = _topElement.getBoundingClientRect();"
+                   @"        return (window.scrollY + rect.top) - (%f * 
rect.height);"
+                   @"    } else {"
+                   @"        return 0;"
+                   @"    }"
+                   @"})()";
+    NSString *js2 = [NSString stringWithFormat:js, 
self.relativeScrollOffsetBeforeRotate, self.relativeScrollOffsetBeforeRotate];
+    int finalScrollOffset = [[self.webView 
stringByEvaluatingJavaScriptFromString:js2] intValue];
 
-    [self.tocVC centerCellForWebViewTopMostSectionAnimated:NO];
+    CGPoint point = CGPointMake(0, finalScrollOffset);
+
+    [self tocScrollWebViewToPoint:point
+                          duration:0
+                       thenHideTOC:NO];
 }
 
 #pragma mark Wikipedia Zero handling

-- 
To view, visit https://gerrit.wikimedia.org/r/150740
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings

Gerrit-MessageType: newchange
Gerrit-Change-Id: Ibdd0f59bde682da46040fa3b0a5b8daab4822721
Gerrit-PatchSet: 1
Gerrit-Project: apps/ios/wikipedia
Gerrit-Branch: master
Gerrit-Owner: Brion VIBBER <br...@wikimedia.org>

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