Update Window_and_Application_API_Spec.md

[marb2000]

Reusing the SetTitleBar method and adding a new Windows.UI.Xaml.Window.TitleBar class to allow customize the TitleBar in WinUI 3 in Desktop

[mdtauk]

Thank you for working on Titlebar customisation!!

I have a question about some of the properties from the current UWP implementation...

// using Windows.UI.ViewManagement;

var titleBar = ApplicationView.GetForCurrentView().TitleBar;

// Set active window colors
titleBar.ForegroundColor = Windows.UI.Colors.White;
titleBar.BackgroundColor = Windows.UI.Colors.Green;
titleBar.ButtonForegroundColor = Windows.UI.Colors.White;
titleBar.ButtonBackgroundColor = Windows.UI.Colors.SeaGreen;
titleBar.ButtonHoverForegroundColor = Windows.UI.Colors.White;
titleBar.ButtonHoverBackgroundColor = Windows.UI.Colors.DarkSeaGreen;
titleBar.ButtonPressedForegroundColor = Windows.UI.Colors.Gray;
titleBar.ButtonPressedBackgroundColor = Windows.UI.Colors.LightGreen;

// Set inactive window colors
titleBar.InactiveForegroundColor = Windows.UI.Colors.Gray;
titleBar.InactiveBackgroundColor = Windows.UI.Colors.SeaGreen;
titleBar.ButtonInactiveForegroundColor = Windows.UI.Colors.Gray;
titleBar.ButtonInactiveBackgroundColor = Windows.UI.Colors.SeaGreen;

Will it be possible to set the colours for the Window Control buttons in both UWP and WinUI Desktop applications?

When introducing custom UI to stand in for the Titlebar, ensuring the control buttons remain visible will be important to maintain, but I did not see any mention of these properties with your proposal update.

https://docs.microsoft.com/en-us/windows/uwp/design/shell/title-bar

[marb2000]

@mdtauk Q: Will it be possible to set the colours for the Window Control buttons in both UWP and WinUI Desktop applications?

A: It won't be possible in this 2020 year. However, there is a workstream working in the Windowing story of project Reunion and we hope this unify the windowing story for UWP and Desktop. Right now, we are creating in XAML an abstraction layer for UWP and Desktop based on CoreWindow and Window Handles, in the future this abstraction layer could use the outcome of the Project Reunion's windowing.

[mdtauk]

@mdtauk Q: Will it be possible to set the colours for the Window Control buttons in both UWP and WinUI Desktop applications?

A: It won't be possible in this 2020 year. However, there is a workstream working in the Windowing story of project Reunion and we hope this unify the windowing story for UWP and Desktop. Right now, we are creating in XAML an abstraction layer for UWP and Desktop based on CoreWindow and Window Handles, in the future this abstraction layer could use the outcome of the Project Reunion's windowing.

Ah fair enough then. Its good that desktop will get some of the modern Titlebar manipulations, if not all of them right away