coreindependentinputsource.md

-api-id	-api-type
T:Windows.UI.Core.CoreIndependentInputSource	winrt class

Windows.UI.Core.CoreIndependentInputSource

-description

Surfaces core input APIs for interoperation scenarios.

-remarks

Create an instance of this class by calling SwapChainBackgroundPanel.CreateCoreIndependentInputSource or SwapChainPanel.CreateCoreIndependentInputSource.

The CoreIndependentInputSource class enables an app to handle input and rendering independent of the XAML UI thread, because you're intentionally providing the input processing logic on a background thread. You must call CreateCoreIndependentInputSource from a non-UI thread, otherwise the CreateCoreIndependentInputSource method call will fail.

Version history

Windows version	SDK version	Value added
1803	17134	DispatcherQueue

-examples

Initializing independent input.

// MainPage.cpp
#include "pch.h"
#include "MainPage.h"
#include <winrt/Windows.System.Threading.h>
#include <winrt/Windows.UI.Core.h>
#include <winrt/Windows.UI.Xaml.Controls.h>

using namespace winrt;
using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;

Windows::Foundation::IAsyncAction m_inputLoopWorker;
...
    // Create a task to register for independent input and begin processing input messages.
    Windows::System::Threading::WorkItemHandler workItemHandler([this](Windows::Foundation::IAsyncAction const& /* action */)
    {
        // The CoreIndependentInputSource will raise pointer events for the specified device types on whichever thread it's created on.
        Windows::UI::Core::CoreIndependentInputSource coreInput{
            MySwapChainPanel().CreateCoreIndependentInputSource(
                Windows::UI::Core::CoreInputDeviceTypes::Mouse |
                Windows::UI::Core::CoreInputDeviceTypes::Touch |
                Windows::UI::Core::CoreInputDeviceTypes::Pen)
        };

        // Register for pointer events, which will be raised on the background thread.
        coreInput.PointerPressed({ this, &MainPage::SCP_OnPointerPressed });
        coreInput.PointerMoved({ this, &MainPage::SCP_OnPointerMoved });
        coreInput.PointerReleased({ this, &MainPage::SCP_OnPointerReleased });

        // Begin processing input messages as they're delivered.
        coreInput.Dispatcher().ProcessEvents(Windows::UI::Core::CoreProcessEventsOption::ProcessUntilQuit);
    });

    // Run task on a dedicated high priority background thread.
    m_inputLoopWorker = Windows::System::Threading::ThreadPool::RunAsync(
        workItemHandler, Windows::System::Threading::WorkItemPriority::High,
        Windows::System::Threading::WorkItemOptions::TimeSliced);
...
void MainPage::SCP_OnPointerPressed(Windows::Foundation::IInspectable const& /* sender */,
    Windows::UI::Core::PointerEventArgs const& /* args */) {}
void MainPage::SCP_OnPointerMoved(Windows::Foundation::IInspectable const& /* sender */,
    Windows::UI::Core::PointerEventArgs const& /* args */) {}
void MainPage::SCP_OnPointerReleased(Windows::Foundation::IInspectable const& /* sender */,
    Windows::UI::Core::PointerEventArgs const& /* args */) {}

// Create a task to register for independent input and begin processing input messages.
auto workItemHandler = ref new WorkItemHandler([this] (IAsyncAction ^)
{
   // The CoreIndependentInputSource will raise pointer events for the specified device types on whichever thread it's created on.
   CoreIndependentInputSource^ coreInput = CreateCoreIndependentInputSource(
      Windows::UI::Core::CoreInputDeviceTypes::Mouse |
      Windows::UI::Core::CoreInputDeviceTypes::Touch |
      Windows::UI::Core::CoreInputDeviceTypes::Pen
   );

   // Register for pointer events, which will be raised on the background thread.
   coreInput->PointerPressed += ref new TypedEventHandler<Object^, PointerEventArgs^>(this, &MyClass::OnPointerPressed);
   coreInput->PointerMoved += ref new TypedEventHandler<Object^, PointerEventArgs^>(this, &MyClass::OnPointerMoved);
   coreInput->PointerReleased += ref new TypedEventHandler<Object^, PointerEventArgs^>(this, &MyClass::OnPointerReleased);

   // Begin processing input messages as they're delivered.
   coreInput->Dispatcher->ProcessEvents(CoreProcessEventsOption::ProcessUntilQuit);
});

// Run task on a dedicated high priority background thread.
m_inputLoopWorker = ThreadPool::RunAsync(workItemHandler, WorkItemPriority::High, WorkItemOptions::TimeSliced);

For more example code of how to use CreateCoreIndependentInputSource and CoreIndependentInputSource, see the DrawingPanel class definition that is part of the XAML SwapChainPanel DirectX interop sample.

-see-also

ICoreInputSourceBase, ICorePointerInputSource, SwapChainPanel, Threading and async programming