[Find in Page] Prevent scrolling past the page edge.

ios/chrome/browser/find_in_page/find_in_page_controller.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/find_in_page/find_in_page_controller.h"
 
 #import <UIKit/UIKit.h>
+#import <cmath>
 
 #include "base/ios/ios_util.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/find_in_page/find_in_page_model.h"
 #import "ios/chrome/browser/find_in_page/js_findinpage_manager.h"
 #import "ios/chrome/browser/web/dom_altering_lock.h"
 #import "ios/web/public/web_state/crw_web_view_proxy.h"
 #import "ios/web/public/web_state/crw_web_view_scroll_view_proxy.h"
@@ skipping 33 matching lines @@
 // Gives find in page more time to complete. Calls |completionHandler| with
 // a BOOL indicating if the find operation was successfull. |completionHandler|
 // can be nil.
 - (void)pumpFindStringInPageWithCompletionHandler:
     (void (^)(BOOL))completionHandler;
 // Processes the result of a single find in page pump. Calls |completionHandler|
 // if pumping is done. Re-pumps if necessary.
 - (void)processPumpResult:(BOOL)finished
               scrollPoint:(CGPoint)scrollPoint
         completionHandler:(ProceduralBlock)completionHandler;
+// Prevent scrolling past the end of the page.
+- (CGPoint)limitOverscroll:(CRWWebViewScrollViewProxy*)scrollViewProxy
+                   atPoint:(CGPoint)point;
 // Returns the associated web state. May be null.
 - (web::WebState*)webState;
 @end
 
 @implementation FindInPageController {
  @private
   // Object that manages find_in_page.js injection into the web view.
   JsFindinpageManager* _findInPageJsManager;
   id<FindInPageControllerDelegate> _delegate;
 
@@ skipping 55 matching lines @@
 
   // Initialize the module with our frame size.
   CGRect frame = [_webViewProxy bounds];
   [_findInPageJsManager setWidth:frame.size.width height:frame.size.height];
 }
 
 - (CRWWebViewScrollViewProxy*)webViewScrollView {
   return [_webViewProxy scrollViewProxy];
 }
 
+- (CGPoint)limitOverscroll:(CRWWebViewScrollViewProxy*)scrollViewProxy
+                   atPoint:(CGPoint)point {
+  CGFloat contentHeight = scrollViewProxy.contentSize.height;
+  CGFloat frameHeight = scrollViewProxy.frame.size.height;
+  CGFloat maxScroll = std::max((CGFloat)0, contentHeight - frameHeight);

[sdefresne, 2015/05/19 13:30:27]

C-style cast are forbidden (and sadly casting constructor like "CGFloat(0)" or
"CGFloat{0}"), I would recommend using "std::max<CGFloat>(0, contentHeight -
frameHeight)" instead.

[justincohen, 2015/05/19 13:57:09]

Done.

+  if (point.y > maxScroll) {
+    point.y = maxScroll;
+  }
+  return point;
+}
+
 - (void)processPumpResult:(BOOL)finished
               scrollPoint:(CGPoint)scrollPoint
         completionHandler:(ProceduralBlock)completionHandler {
   if (finished) {
     [_delegate willAdjustScrollPosition];
+    scrollPoint = [self limitOverscroll:[_webViewProxy scrollViewProxy]
+                                atPoint:scrollPoint];
     [[_webViewProxy scrollViewProxy] setContentOffset:scrollPoint animated:YES];
     if (completionHandler)
       completionHandler();
   } else {
     [self performSelector:@selector(startPumpingWithCompletionHandler:)
                withObject:completionHandler
                afterDelay:kRecurringPumpDelay];
   }
 }
 
@@ skipping 41 matching lines @@
 }
 
 - (void)pumpFindStringInPageWithCompletionHandler:
     (void (^)(BOOL))completionHandler {
   base::WeakNSObject<FindInPageController> weakSelf(self);
   [_findInPageJsManager pumpWithCompletionHandler:^(BOOL finished,
                                                     CGPoint point) {
     base::scoped_nsobject<FindInPageController> strongSelf([weakSelf retain]);
     if (finished) {
       [[strongSelf delegate] willAdjustScrollPosition];
+      point = [strongSelf limitOverscroll:[strongSelf webViewScrollView]
+                                  atPoint:point];
       [[strongSelf webViewScrollView] setContentOffset:point animated:YES];
     }
     completionHandler(finished);
   }];
 }
 
 - (void)findNextStringInPageWithCompletionHandler:
     (ProceduralBlock)completionHandler {
   [self initFindInPage];
   base::WeakNSObject<FindInPageController> weakSelf(self);
   [_findInPageJsManager nextMatchWithCompletionHandler:^(CGPoint point) {
     base::scoped_nsobject<FindInPageController> strongSelf([weakSelf retain]);
     [[strongSelf delegate] willAdjustScrollPosition];
-    CGFloat contentHeight = [strongSelf webViewScrollView].contentSize.height;
-    CGFloat frameHeight = [strongSelf webViewScrollView].frame.size.height;
-    CGFloat maxScroll = fmax(0, contentHeight - frameHeight);
-    if (point.y > maxScroll) {
-      point.y = maxScroll;
-    }
+    point = [strongSelf limitOverscroll:[strongSelf webViewScrollView]
+                                atPoint:point];
     [[strongSelf webViewScrollView] setContentOffset:point animated:YES];
     if (completionHandler)
       completionHandler();
   }];
 }
 
 // Highlight the previous search match, update model and scroll to match.
 - (void)findPreviousStringInPageWithCompletionHandler:
     (ProceduralBlock)completionHandler {
   [self initFindInPage];
   base::WeakNSObject<FindInPageController> weakSelf(self);
   [_findInPageJsManager previousMatchWithCompletionHandler:^(CGPoint point) {
     base::scoped_nsobject<FindInPageController> strongSelf([weakSelf retain]);
     [[strongSelf delegate] willAdjustScrollPosition];
+    point = [strongSelf limitOverscroll:[strongSelf webViewScrollView]
+                                atPoint:point];
     [[strongSelf webViewScrollView] setContentOffset:point animated:YES];
     if (completionHandler)
       completionHandler();
   }];
 }
 
 // Remove highlights from the page and disable the model.
 - (void)disableFindInPageWithCompletionHandler:
     (ProceduralBlock)completionHandler {
   if (![self canFindInPage])
@@ skipping 103 matching lines @@
 
 - (BOOL)canReleaseDOMLock {
   return NO;
 }
 
 - (void)releaseDOMLockWithCompletionHandler:(ProceduralBlock)completionHandler {
   NOTREACHED();
 }
 
 @end