[Webkit-unassigned] [Bug 165225] UIViewController with WKWebView presented modally causes the presented UIViewController to be dismissed.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=165225

--- Comment #30 from Brad Wright <bwright2 at apple.com> ---
(In reply to comment #29)
> (In reply to comment #28)
> > (In reply to comment #26)
> > > (In reply to comment #25)
> > > > Comment on attachment 303130 [details]
> > > > Patch
> > > > 
> > > > View in context:
> > > > https://bugs.webkit.org/attachment.cgi?id=303130&action=review
> > > > 
> > > > > Source/WebKit2/UIProcess/ios/forms/WKFileUploadPanel.mm:391
> > > > > +    // dismiss any viewController that is being presented. This is works all VC, popovers, etc.
> > > 
> > > This is works for all VC.  Missed the for, in the comment.
> > > > 
> > > > Normally we would want to use a capital D in this kind of sentence-style
> > > > comment.
> > > > 
> > > > VC is not normally an abbreviation we use for view controller in WebKit code.
> > > > 
> > > > "This is works all", is not grammatically correct.
> > > > 
> > > > > Source/WebKit2/UIProcess/ios/forms/WKFileUploadPanel.mm:394
> > > > > +    UIViewController *presentedViewController = [UIViewController _viewControllerForFullScreenPresentationFromView:_view];
> > > > > +    if (presentedViewController)
> > > > > +        [presentedViewController dismissViewControllerAnimated:NO completion:nil];
> > > > 
> > > > Would be nice to define the variable inside the "if" since this is C++ code.
> > > > In fact, I personally would use auto instead of writing out UIViewController
> > > > * for the type of the variable.
> > > > 
> > > > > Source/WebKit2/UIProcess/ios/forms/WKFileUploadPanel.mm:508
> > > > > +    // Clear out any previous view controller reference, to prevent calling dismiss on a view controller that
> > > > > +    // was no longer being presented. Don't save a reference to the UIDocumentMenuViewController as it is self dismissing.
> > > > > +    _presentationViewController = nil;
> > > > 
> > > > I don’t understand this comment and therefore don’t understand the code.
> > > 
> > > So what happening is that the _presentationViewController is used to called
> > > in:
> > > 
> > > - (void)_dismissDisplayAnimated:(BOOL)animated
> > > {
> > >     if (_presentationPopover) {
> > >         [_presentationPopover dismissPopoverAnimated:animated];
> > >         [_presentationPopover setDelegate:nil];
> > >         _presentationPopover = nil;
> > >     }
> > > 
> > >     if (_presentationViewController) {
> > >         [_presentationViewController dismissViewControllerAnimated:animated
> > > completion:^{
> > >             _presentationViewController = nil;
> > >         }];
> > >     }
> > > }
> > > 
> > > 
> > > The UIDocumentMenuViewController dismisses itself, so when
> > > _presentationViewController dismissViewControllerAnimated:animated is called
> > > in this function, it dismisses the WKWebView when is presented modally. 
> > > That's why it's set to nil in this function, so that the errant code path is
> > > never executed.
> > > > 
> > > > On iPhone, the method called just before this will call
> > > > _presentFullscreenViewController. Then this line of code will clear out the
> > > > reference to that just-presented view controller. Given that, why does this
> > > > comment talk about clearing out a "previous view controller reference"?
> > 
> > 
> > Inside the call stack this is the reference that needs to be cleared out.
> > 
> > 1. We start here inside:
> > - (void)_showDocumentPickerMenu
> > 2.Then this is called:
> > - (void)_presentMenuOptionForCurrentInterfaceIdiom:(UIViewController
> > *)viewController
> > 3. Finally, inside here the property _presentationViewController is set.
> > - (void)_presentFullscreenViewController:(UIViewController *)viewController
> > animated:(BOOL)animated
> > {
> >     ...
> >     _presentationViewController = [UIViewController 
> > ...
> > }
> > 
> > 4. When we return up the stack, we need to set _presentationViewController back to nil.
> > 
> > - (void)_showDocumentPickerMenu
> > 
> > 
> > I put this comment and the nil reference as close together as possible to
> > minimize future errors.

The above code is not C++, but Objective-C.  I know this is a mixed Objective-C and C++  .mm file, but I'm not aware of any memory overhead penalty for this pointer variable in Objective-C.

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