Allow settings panes to derive from SettingsFlyout

[Andy-Wilkinson]

A user has requested that they would like to be able to derive their settings panes from SettingsFlyout (so that the Visual Studio designer shows the settings pane in context). Currently this results in the Okra App Framework embedding the user's SettingsFlyout inside the Okra created SettingsFlyout. It is proposed that Okra should not create its own flyout in this case.

[Andy-Wilkinson]

Really like the idea of being able to derive from SettingsFlyout - this would be the ideal solution for development with the Visual Studio designer.

The issue is that multi-page settings panes would result in the settings flyout animations when navigating between pages.

Solutions would be,

• Only support inheriting from SettingsFlyout for single page settings panes - for multi-page panes you would have to use the current method.
• Support multi-page settings panes, but have the incorrect fly out/in on page changed.
• Strip out the content from the SettingsFlyout and inject it into Okra's own flyout - this would solve the animation issue, but be a bit of a hack and would probably be incompatible with code-behind.

[Andy-Wilkinson]

As a starting point for the Okra App Framework v1.0 I aim to implement the first point above (only support inheriting from SettingsFlyout for single page settings panes). If attempts are made at navigation then an exception will be thrown, and the alternative approach (settings pages not derived from SettingsFlyout) should be used.

This will allow most use-cases (typically single page settings panes) to derive from SettingsFlyout, whilst minimising any breaking changes if a more complete implementation is introduced in a future release.

[Andy-Wilkinson]

Have managed to identify a way of allowing full support (including multi-page) for SettingsFlyout derived settings panes. This will be the approach used in the next update.