You can resize the window to see how it changes. Even at load size (well… depending on your browser’s window size obviously) you can see how the ScrollViewer “inner-scrollable” size is taller than the vertical stackpanel and at certain aspect ratios it’s shorter, so you can’t actually see all stackpanel’s content.
Not 100% sure if this is not me missing something out as I’m pretty new to this engine. But I’ve been playing around for a while now with this.
The UI I’m implementing is quite a bit more complex and supporting both landscape and portrait than what’s shown on the PG. I guess I could use relative sizes on every control checking for aspect ratio to change that relative size, but I’d like to get it working by having the idealWidth if possible.