Provide delegate SPI for clients to notify WebKit about content inset changes

[Brent Fulgham]

WebKit clients may sometimes modify the contents insets of the view while the user is performing scroll gestures. We should have a delegate method that WebKit can use to ask the host application if any such changes will happen so that we can properly animate to the final window state.

[Brent Fulgham]

<rdar://problem/21602741>

[Brent Fulgham]

Created attachment 255883 [details]
Patch

[Sam Weinig]

Comment on attachment 255883 [details]
Patch

Given the limited use case, this should start as SPI on WKUIDelegatePrivate.h

[Brent Fulgham]

Created attachment 256015 [details]
Patch

[Darin Adler]

Comment on attachment 256015 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256015&action=review

> Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm:1474
> +        UIEdgeInsets contentInset = [self _computedContentInset];
> +
> +        id<WKUIDelegatePrivate> uiDelegatePrivate = static_cast<id <WKUIDelegatePrivate>>([self UIDelegate]);
> +        if ([uiDelegatePrivate respondsToSelector:@selector(_webView:finalObscuredInsetsForScrollView:withVelocity:targetContentOffset:)])
> +            contentInset = [uiDelegatePrivate _webView:self finalObscuredInsetsForScrollView:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];

Would be better to use else so we don’t unnecessarily call _computedContentInset every time.

[Brent Fulgham]

Comment on attachment 256015 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=256015&action=review

>> Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm:1474
>> +            contentInset = [uiDelegatePrivate _webView:self finalObscuredInsetsForScrollView:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
> 
> Would be better to use else so we don’t unnecessarily call _computedContentInset every time.

Good idea! Will do.

[Brent Fulgham]

Committed r186237: <http://trac.webkit.org/changeset/186237>