Public Access
jaap-jan
36b8a23020
The banner has never worked. It went into MainWindow's fourth row with no data context of its own, so it inherited the shell's — and it is the one control in that file typed to a screen's view model rather than to MainWindowViewModel, because it is the only one with a layout suite that hosts it over UpdateViewModel alone. Compiled bindings type-check against x:DataType at runtime, so every binding inside it resolved against the wrong object and failed the way a compiled binding does: quietly. No headline, and DismissBannerCommand and RestartNowCommand both null. A button with a null command is enabled, hovers, depresses and does nothing, which is why this looked like a hit-testing problem and why the WebView was the first suspect. It is not one. The strip is a sibling row for the reason the occlusion rule gives and that arrangement is correct — the terminal's rectangle is never covered, only shortened. What was actually on offer was an announcement that an update had been downloaded, with two buttons that refused to install it and no way to make it go away either. The preferences screen's RESTART NOW worked throughout, because it binds Updates.RestartNowCommand from the shell's own context, which is the contrast that pins the cause. The context is set on the banner itself and IsVisible loses its Updates. prefix with it, because a data context on an element resolves that element's other bindings too — the rule the page area's wrappers upstairs exist to work around. Those wrappers are needed because IsHostsScreen and its siblings belong to the shell; IsBannerShowing belongs to the banner's own view model, so there is nothing to wrap here. Neither existing suite could have caught it. A layout test supplies the data context it is measuring, which is exactly the assumption that was wrong, and the shell suite has no visual tree — its project file already says it does not cover whether the XAML binds to the right names. So the new test asserts the wiring rather than the layout: a real shell over the ready-update fake, MainWindow constructed and never shown, and the banner asked what context it got, whether it is visible and whether RESTART NOW carries a command. Checked failing with the one attribute removed. Constructing the window is safe where showing it is not, and nothing here needs it shown: a data context propagates when it is set, not when the tree is measured.