[Webkit-unassigned] [Bug 192644] New: WKWebView returns invalid window screen width and height in classic iPad apps

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=192644

            Bug ID: 192644
           Summary: WKWebView returns invalid window screen width and
                    height in classic iPad apps
           Product: WebKit
           Version: WebKit Local Build
          Hardware: iPhone / iPad
                OS: iOS 12
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore JavaScript
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: andrew at planetaryscale.com

Created attachment 357186

  --> https://bugs.webkit.org/attachment.cgi?id=357186&action=review

Sample iPad app that runs in classic mode

Overview:

WKWebView returns incorrect values for window.screen.width and window.screen.height in JavaScript when inside iPad apps running in a scaled/non-native mode ("classic"). This is a regression from UIWebView behavior.

Steps to Reproduce:

* Open attached sample app on a 10.5", 11", or 12.9" iPad or iPad simulator.
* Note difference between values in the top WKWebView versus the bottom UIWebView.

Actual Results:

In the WKWebView window.screen.width is 320 and window.screen.height is 480.
In the UIWebView window.screen.width is 768 and window.screen.height is 1024.

Expected Results:

The screen size should report as 768x1024, which is the screen's reference bounds.

Configuration:

Found on iOS 12.1 both in Simulator and on device, although haven't regressed it. Xcode 10.1 (10B61).

Additional Notes:

320x480 is the default scaling resolution for iPhone-only apps whether on iPhones or iPads. 768x1024 is the scaling resolution of iPad apps on iPads, as that was the resolution of the first iPad.

This looks like it was a deliberate change in https://bugs.webkit.org/show_bug.cgi?id=150763, but I don't have any insight as to why this change was made.

This breaks some existing functionality when migrating from UIWebView to WKWebView in scaled iPad apps. Workaround is to support the native resolution of each iPad, but in legacy iPad apps that process may take longer than moving to WKWebView.

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