How to use FileSavePicker with C++/WinRT for desktop app?

[ZhouJJJKKK]

I want to open a dialog and save files with C++/WinRT for desktop app, here is my code:

Windows::Foundation::IAsyncAction click_button(Windows::Foundation::IInspectable const& sender, winrt::Microsoft::UI::Xaml::RoutedEventArgs const& e) {
    Windows::Storage::Pickers::FileSavePicker savepicker;
    savepicker.SuggestedStartLocation(Windows::Storage::Pickers::PickerLocationId::DocumentsLibrary);
    auto plainTextExtensions = winrt::single_threaded_vector<winrt::hstring>();
    plainTextExtensions.Append(winrt::param::hstring(L".jpg"));
    savepicker.FileTypeChoices().Insert(L"jpg", plainTextExtensions);
    savepicker.SuggestedFileName(L"new ducument");
    co_await winrt::resume_background();
    auto file = co_await savepicker.PickSaveFileAsync();
    co_await resume_foreground(DispatcherQueue());
}

But no dialog showed, and no error occurred.
I guess the savepicker.PickSaveFileAsync() function was blocked, how to resolve it?

[andrewleader]

Hi @ZhouJJJKKK, sorry for the delayed response. In desktop-based apps, you have to use InitializeWithWindow on pickers like FilePicker to let the picker know which window (hwnd) it should display over.

    auto picker = winrt::Windows::Storage::Pickers::FileOpenPicker();
    picker.as<IInitializeWithWindow>()->Initialize(hwnd);
    ...

Here's some more info: https://docs.microsoft.com/windows/apps/desktop/modernize/desktop-to-uwp-supported-api#classes-that-use-iinitializewithwindow

[nickrandolph]

I'm pretty certain this isn't the first time this feedback has been given - is it really that hard to provide a clean abstraction where developers aren't responsible for cobbling together WinRT pickers/dialogs with the hwnd of the window. This is a) super ugly to have to do every time and b) not intuitive to developers trying to use this for the first time

[andrewleader]

@nickrandolph you're correct, we've got this feedback tracked in our internal productboard (which we're hopefully sharing our public portal soon, it helps us aggregate feedback across a variety of sources). We logged your previous feedback from #466 (comment) in our item in productboard.

We're heads-down focused on finishing 1.0 right now, this is definitely something we'd like to improve in the future.

[ZhouJJJKKK]

thank you @andrewleader for the guide. The picker's UI successfully showed in my desktop program.

[benschop-it]

I still get a crash calling FileSavePicker.PickSaveFileAsync(). VS2022, 10.0.20348.0, CPPWinRT 2.0.220131.2, despite using InitializeWithWindow. I am testing with this project: https://github.com/robmikh/Win32CaptureSample.git. It crashes when you clikc on "Take Snapshot". I've upgraded to the versions mentioned above but it made no difference. The exception I get is Invalid window handle.