Wt

With wt 4.9.1, a WStackedWidget in a layout can lose vertical scrollbars on animated transitions. This occurs with both flex and javascript layout implementations.

The attached test program demonstrates the issue. You can choose an animation and then switch between layers using the radio buttons. The application displays two WStackedWidgets. One is in a Flex layout, the other is in a JavaScript layout. The "No Animation" case should work fine with both layouts in 4.9.1, but will lose vertical scrollbars with the animations.

As a note, the Flex layout will appear to work correctly if you visit the layers with the "No Animation" case before trying the animated cases. That's because a height will be set as a side-effect of visiting the layers.
Also, the javascript case will appear to work initially in some cases, but will fail on subsequent transitions.

I've attached two patches for your review, which I believe help with both cases. The first appears sufficient to fix layouts with the javascript implementation. The second addresses flex layouts.

This is largely a follow-up to #7082 with an improved example program, an updated patch for the javascript implementation and a new patch for the flex implementation. Testing was done with Wt-4.9.1. I also re-tested with the wt-homepage example and there appear to be no regressions. See #6788 for the test procedure.