private async static ValueTask <(bool left, bool right)> GetLeftRightCtrlStateAsync(uint delay, CancellationToken token)
{
// this is used purely for debugging and so we utilize
// native CreateTimerQueueTimer with WT_EXECUTEINPERSISTENTTHREAD
// for keyboard polling here, because we don't want
// to pollute ThreadPool threads with AttachThreadInput other user32 calls
var tcs = new TaskCompletionSource <(bool, bool)>(TaskCreationOptions.RunContinuationsAsynchronously);
using var rego = token.Register(() => tcs.SetCanceled(), useSynchronizationContext: false);
WinApi.WaitOrTimerCallbackProc timerCallback = delegate
{
try
{
// attach the to the foreground thread to read the keyboard status
var currentThread = WinApi.GetCurrentThreadId();
var foregroundWindow = WinApi.GetForegroundWindow();
var foregroundThread = WinApi.GetWindowThreadProcessId(foregroundWindow, out uint foregroundProcess);
var attached = WinApi.AttachThreadInput(foregroundThread, currentThread, true);
try
{
var leftCtrl = (WinApi.GetAsyncKeyState(WinApi.VK_LCONTROL) & 0x8000) != 0;
var rightCtrl = (WinApi.GetAsyncKeyState(WinApi.VK_RCONTROL) & 0x8000) != 0;
tcs.TrySetResult((leftCtrl, rightCtrl));
}
finally
{
if (attached)
{
WinApi.AttachThreadInput(foregroundThread, currentThread, false);
}
}
}
catch (Exception ex)
{
tcs.TrySetException(ex);
}
};
var gcHandle = GCHandle.Alloc(timerCallback);
IntPtr timerHandle = IntPtr.Zero;
try
{
if (!WinApi.CreateTimerQueueTimer(
out timerHandle,
IntPtr.Zero,
timerCallback,
IntPtr.Zero, delay, 0,
(UIntPtr)(WinApi.WT_EXECUTEINPERSISTENTTHREAD | WinApi.WT_EXECUTEONLYONCE)))
{
throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
}
return(await tcs.Task);
}
finally
{
if (timerHandle != IntPtr.Zero)
{
WinApi.DeleteTimerQueueTimer(IntPtr.Zero, timerHandle, IntPtr.Zero);
}
gcHandle.Free();
}
}