Communication between WinApi and hosted WinUI

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youki asked May 10, '22 youki commented May 17, '22

Communication between WinApi and hosted WinUI

Hello,
i have a few question for hosting a WinUI UI as an editor for my WinApi background app.

https://docs.microsoft.com/de-de/windows/apps/desktop/modernize/host-custom-control-with-xaml-islands-cpp

Is there a possibility that I will have problems when I want the XAML UI to communicate with the WinApi part?
(I want to save/ edit values in the XAML UI in a for i.e. resource file and tell the WinApi part to read the settings from the resource file [or may be a xml])
Only WinUI 2 controls are supported? I will need listviews, dropdown boxes, radio buttons and something like a navigation view [slide menu], i won't have any problems there?

windows-api c++windows-app-sdk

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Answer 1 · 2022-05-10T08:08:58.84Z

Castorix31 answered May 10, '22 youki commented May 17, '22

XAML Islands for WinUI 3 is not ready yet : 1-under-consideration
(some XAML controls can be embedded like I explained in this thread, but it is just a workaround and not really usable)

You should do the reverse, Win32 APIs in a WinUI 3 app
(as unpackaged WinUI 3 apps are standard Win32 apps, you can do anything a C++/Win32 app can do)
From what you wrote in other threads, you can put it in background (just no window), add a Tray icon with Shell_NotifyIcon, etc...

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youki · May 10 at 10:53 AM

Will it also be possible to free the UI Memory, if the UI is closed and the application stays running in the background (system tray)?

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Castorix31 youki · May 10 at 01:47 PM

I don't see what you mean by "free the UI Memory", because WinUI 3 apps don't use more memory than other Win32 apps
I just checked with Process Explorer, and I did not notice anything particular... (Private Bytes, Working Set, User/GDI objects, Handles,...)

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youki · May 16 at 08:46 PM

How can i add the message loop for handling the xaml window and the context menu?

Is it like before, registering a window class and a new window, so I’m using the message loop of the WinApi window?

Until now i’ve created an unpackaged WinUI application, the context menu and i'm hiding it by "ShowWindow(handle, SW_HIDE)".

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Castorix31 youki · May 17 at 02:41 PM

For Shell_NotifyIcon, you just subclass the window with SetWindowSubclass where you intercept your custom message to display the context menu on WM_CONTEXTMENU or WM_RBUTTONUP

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youki Castorix31 · May 17 at 06:10 PM

Cool,
Works!

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Answer 2 · 2022-05-12T14:48:54.223Z

youki answered May 12, '22 youki edited May 12, '22

Even if the memory consumption of the UI is very small, wouldn't it still be possible to free up the memory with WinUI as a component?
The UI only serves as an editor and is rarely used (0.000001% of the time).

Forget the following: *> Aha ok, i understand.

I've just seen the message "This UWP process group is suspending processes to improve system performance" in the taskmanager for OneNote. So this is the default behaviour, if you minimize/close the UI in UWP (?!).*

image.png (15.7 KiB)

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