WPF shows that some windows in multithreading will be locked in the PenThreadWorker constructor #928
Description
- .NET Core Version: 3.0.100-preview5-011568
- Windows version: 1903 18362.145
- Does the bug reproduce also in WPF for .NET Framework 4.8?: Maybe
Problem description:
WPF will initialize pen thread when the window initializing. But I find the window may be locked in PenThreadWorker constructor.
The UnsafeNativeMethods.CreateResetEvent will lock the thread.
Actual behavior:
I use multithreading to create some windows by this code and maybe the thread be locked in PenThreadWorker constructor.
The Demo code
public partial class App : Application
{
/// <inheritdoc />
protected override void OnStartup(StartupEventArgs e)
{
var thread = new Thread(() =>
{
var mainWindow = new MainWindow();
mainWindow.Show();
Dispatcher.Run();
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
base.OnStartup(e);
}
}The step
-
Run the code
-
Use the VisualStudio to suspend the application
Maybe you can find the application only create a Stylus Input thread and show only a main window and the other main window and the thread be locked in PenThreadWorker constructor and the window can not show
Why I need multithreading to show the windows? I need the splash window to show the welcome page and then I should show the main window in other thread to do the bussiness code and I should close the splash window when the main window showed.
But I found some users could not show the main window and the main window be lock in PenThreadWorker constructor.
I use dnspy to suspend the application and find the code run in PenThreadWorker constructor and the UnsafeNativeMethods.CreateResetEvent will lock the thread.
PenThreadWorker..ctor()
PenThread..ctor()
PenThreadPool.GetPenThreadForPenContextHelper(PenContext penContext)
PenThreadPool.GetPenThreadForPenContext(PenContext penContext)
WispTabletDeviceCollection.UpdateTabletsImpl()
WispTabletDeviceCollection.UpdateTablets()
WispTabletDeviceCollection..ctor()
WispLogic.get_WispTabletDevices()
WispLogic.RegisterHwndForInput(InputManager inputManager, PresentationSource inputSource)
HwndStylusInputProvider..ctor(HwndSource source)
HwndSource.Initialize(HwndSourceParameters parameters)
HwndSource..ctor(HwndSourceParameters parameters)
PresentationFramework.dll!System.Windows.Window.CreateSourceWindow(bool duringShow)
PresentationFramework.dll!System.Windows.Window.CreateSourceWindowDuringShow()
PresentationFramework.dll!System.Windows.Window.ShowHelper(object booleanBox) Expected behavior:
The UnsafeNativeMethods.CreateResetEvent do not lock the thread
Minimal repro:
Create a empty WPF application and then change the app.xaml.cs code
public partial class App : Application
{
/// <inheritdoc />
protected override void OnStartup(StartupEventArgs e)
{
var thread = new Thread(() =>
{
var mainWindow = new MainWindow();
mainWindow.Show();
Dispatcher.Run();
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
base.OnStartup(e);
}
}Run the code and maybe you can find one of the main window can not show and it stop in UnsafeNativeMethods.CreateResetEvent and I wait for a hour but it can not run.