UWP InkCanvas 捕获事件但不显示它们

Question

我最近在本地修改了 vmulti 项目 https://github.com/djpnewton/vmulti 的一个分支，以便在带有 VS2019 社区的 Windows 10 中工作，并对其进行了一些改进，包括为笔的 HID 报告添加笔尖和桶压力，以及最多支持 4 个操纵杆，这样我就可以通过我已经用 C++ 编写的服务器通过 TCP/IP 将鼠标/键盘/触摸/笔/操纵杆事件传递到另一个系统。

我现在正在为它编写一个 UI，要么将 Win32 C++ 与 Xaml Islands 一起使用，要么将使用 UWP，两者都将使用来自单独 UWP dll 项目的 Xaml UserControl。

我想使用带有笔/触摸/鼠标的 UWP InkCanvas 来仅收集笔划，如果可能的话，我根本不希望笔划显示在屏幕上。

现在我的代码如下所示：

MainScreen::MainScreen()
{
    InitializeComponent();
    this->inkCanvas1->InkPresenter->InputDeviceTypes = Windows::UI::Core::CoreInputDeviceTypes::Mouse | Windows::UI::Core::CoreInputDeviceTypes::Pen | Windows::UI::Core::CoreInputDeviceTypes::Touch;      
    this->inkCanvas1->InkPresenter->StrokeInput->InkPresenter->InputProcessingConfiguration->Mode = Windows::UI::Input::Inking::InkInputProcessingMode::Erasing;
    this->inkCanvas1->InkPresenter->InputProcessingConfiguration->Mode = Windows::UI::Input::Inking::InkInputProcessingMode::Erasing;

    this->inkCanvas1->InkPresenter->StrokeInput->StrokeStarted += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeStarted);
    this->inkCanvas1->InkPresenter->StrokeInput->StrokeContinued += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeContinued);
    this->inkCanvas1->InkPresenter->StrokeInput->StrokeEnded += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeEnded);

    this->inkCanvas1->Opacity = 0.002;

    Windows::UI::Input::Inking::InkDrawingAttributes^ drawingAttributes = inkCanvas1->InkPresenter->CopyDefaultDrawingAttributes();
    drawingAttributes->DrawAsHighlighter = true;
    Windows::UI::Color color1 = Windows::UI::Color();
    color1.R = 0;
    color1.G = 0;
    color1.B = 0;
    color1.A = 0;
    drawingAttributes->Color = color1;
    Windows::Foundation::Size size1 = drawingAttributes->Size;
    size1.Width = 0.0;
    size1.Height = 0.0;
    drawingAttributes->Size = size1;
    inkCanvas1->InkPresenter->UpdateDefaultDrawingAttributes(drawingAttributes);
}

void VMulti_UI_Xaml::MainScreen::OnStrokeStarted(Windows::UI::Input::Inking::InkStrokeInput^ sender, Windows::UI::Core::PointerEventArgs^ args)
{   
    std::wcout << "Stroke Started: " << args->CurrentPoint->Position.X << "," << args->CurrentPoint->Position.Y << std::endl;
    args->Handled = true;
    inkCanvas1->InkPresenter->StrokeContainer->Clear();
}


void VMulti_UI_Xaml::MainScreen::OnStrokeContinued(Windows::UI::Input::Inking::InkStrokeInput^ sender, Windows::UI::Core::PointerEventArgs^ args)
{
    std::wcout << "Stroke Continued: " << args->CurrentPoint->Position.X << "," << args->CurrentPoint->Position.Y << std::endl;
    args->Handled = true;
    inkCanvas1->InkPresenter->StrokeContainer->Clear();
}


void VMulti_UI_Xaml::MainScreen::OnStrokeEnded(Windows::UI::Input::Inking::InkStrokeInput^ sender, Windows::UI::Core::PointerEventArgs^ args)
{
    std::wcout << "Stroke Ended: " << args->CurrentPoint->Position.X << "," << args->CurrentPoint->Position.Y << std::endl;
    args->Handled = true;
    inkCanvas1->InkPresenter->StrokeContainer->Clear();
}

这几乎已经足够了，但您正在绘制的当前笔画仍会显示。我也想让它消失。在 StrokeInput 的笔画事件上将设置处理为 true 不会做任何事情来阻止笔画被绘制。清除每个事件的笔画会清除所有内容，但您正在绘制的当前笔画除外，我也想删除它。将 InkCanvas 的不透明度显示为低于 0.002 的任何值似乎会使事件以某种方式无法触发。

所以我想知道，我怎样才能摆脱所有绘制的笔画，包括当前在 InkCanvas 上绘制的笔画？我只是通过捕获事件，我不想在屏幕上绘制。

Answer 1

找到了，就像有时候 .NET 的事情一样，你不能只在 InitializeComponent() 之后进行某些调用，你必须等到 Loaded，下面的更新代码将隐藏当前的墨迹。

更新代码：

MainScreen::MainScreen()
{
    InitializeComponent();
    this->inkCanvas1->InkPresenter->InputDeviceTypes = Windows::UI::Core::CoreInputDeviceTypes::Mouse | Windows::UI::Core::CoreInputDeviceTypes::Pen | Windows::UI::Core::CoreInputDeviceTypes::Touch;  
    this->inkCanvas1->InkPresenter->StrokeInput->InkPresenter->InputProcessingConfiguration->Mode = Windows::UI::Input::Inking::InkInputProcessingMode::Erasing;
    this->inkCanvas1->InkPresenter->InputProcessingConfiguration->Mode = Windows::UI::Input::Inking::InkInputProcessingMode::Erasing;

    this->inkCanvas1->InkPresenter->StrokeInput->StrokeStarted += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeStarted);
    this->inkCanvas1->InkPresenter->StrokeInput->StrokeContinued += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeContinued);
    this->inkCanvas1->InkPresenter->StrokeInput->StrokeEnded += ref new Windows::Foundation::TypedEventHandler<Windows::UI::Input::Inking::InkStrokeInput^, Windows::UI::Core::PointerEventArgs^>(this, &VMulti_UI_Xaml::MainScreen::OnStrokeEnded);

    this->inkCanvas1->Opacity = 0.002;

    this->Loaded += ref new Windows::UI::Xaml::RoutedEventHandler(this, &VMulti_UI_Xaml::MainScreen::OnLoaded);
}

void VMulti_UI_Xaml::MainScreen::OnLoaded(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
    Windows::UI::Input::Inking::InkDrawingAttributes^ drawingAttributes = inkCanvas1->InkPresenter->CopyDefaultDrawingAttributes();
    drawingAttributes->DrawAsHighlighter = true;
    Windows::UI::Color color1 = Windows::UI::Color();
    color1.R = 0;
    color1.G = 0;
    color1.B = 0;
    color1.A = 0;
    drawingAttributes->Color = color1;
    Windows::Foundation::Size size1 = drawingAttributes->Size;
    size1.Width = 0.001;
    size1.Height = 0.001;
    drawingAttributes->Size = size1;
    inkCanvas1->InkPresenter->UpdateDefaultDrawingAttributes(drawingAttributes);

    inkCanvas1->InkPresenter->InputConfiguration->IsEraserInputEnabled = true;
}