UWP Printing

Hoping to get UWP print functionality in my Unity UWP app by following the steps in

stackoverflow question 9074684 - how-to-print-in-uwp-app


Here's the relevant parts of my app:

Code (CSharp):

1. #if (ENABLE_IL2CPP && UNITY_WSA_10_0)
2.     void InitializePrinting()
3.     {
4.         printMan = PrintManager.GetForCurrentView();
5.         printMan.PrintTaskRequested += PrintTaskRequested;
6.         printDoc = new PrintDocument();
7.         printDocSource = printDoc.DocumentSource;
8. ......
9.  
10. void OnPrint()
11. {
12. UnityEngine.WSA.Application.InvokeOnUIThread(async () =>
13.             {
14.                 InitializePrinting();
15.             }, true);
16.  
17. }

However program is hanging when new PrintDocument() is called...

Any ideas, anyone?

 

So, offhand I noticed your calling InvokeOnUIThread() with true for waitUntilDone parameter; this should be false.
This is blocking the calling thread and is probably causing the deadlock

 

Thanks for responding!

I did change the parameter to false, but still seems to hang when creating the PrintDoc object. Also I'm calling the InitializePrinting() function from an OnEnable

Code (CSharp):

1. #if (ENABLE_IL2CPP && UNITY_WSA_10_0)
2.     void InitializePrinting()
3.     {
4.         printMan = PrintManager.GetForCurrentView();
5.         printMan.PrintTaskRequested += PrintTaskRequested;
6.         printDoc = new PrintDocument();
7.         printDocSource = printDoc.DocumentSource;
8. ......
9. void OnEnable()
10. {
11. UnityEngine.WSA.Application.InvokeOnUIThread(async () =>
12.             {
13.                 InitializePrinting();
14.             }, false);
15. }

 

I quickly tried this code out but wasn't able to repro the deadlock. So a couple additional questions:

- Are you building a "XAML Project" for UWP?
Since PrintDocument is a XAML control, you'll need to use the project type. I tried it with D3D and just got a RPC_E_WRONG_THREAD error (but didn't deadlock).

- What version of Unity are you using?
- Are you using IL2CPP or .NET back end (if on a 217.4 or older release)?

 

sorry for the delay in responding..

I switched from a D3D to a XAML project
using Unity 2018.3.13f1
with IL2CPP backend

When printDoc = new PrintDocument(); is called, I'm getting an exception:

Exception: Exception of type 'System.Exception' was thrown.
at Windows.UI.Xaml.Printing.PrintDocument..ctor () [0x00000] in <00000000000000000000000000000000>:0
at ScreenShotPopUp.InitializePrinting2 () [0x00000] in <00000000000000000000000000000000>:0
at ScreenShotPopUp+<DoScreenshot>d__65.MoveNext () [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) [0x00000] in <00000000000000000000000000000000>:0

#if (ENABLE_IL2CPP && UNITY_WSA_10_0)
void InitializePrinting()
{
// Printing
LogManager.mInstance.Log("ScreenShotPopuUp.InitializePrinting");

LogManager.mInstance.Log("ScreenShotPopuUp.InitializePrinting getting printMan");
printMan = PrintManager.GetForCurrentView();
LogManager.mInstance.Log("ScreenShotPopuUp.InitializePrinting adding PrintTaskRequested");
printMan.PrintTaskRequested += PrintTaskRequested;

LogManager.mInstance.Log("ScreenShotPopuUp.InitializePrinting Done");

InitializePrinting2();
}

void InitializePrinting2()
{
// Build a PrintDocument and register for callbacks
LogManager.mInstance.Log("ScreenShotPopuUp.InitializePrinting2 creating printdocument");
printDoc = new PrintDocument();

 

Are you calling InitializePrinting() on the UI thread? From this recent code you pasted it doesn't seem like you are, whereas in your original post you did.

Code (CSharp):

1.  
2. void Start()
3. {
4. #if (ENABLE_IL2CPP && UNITY_WSA_10_0)
5.  
6. UnityEngine.WSA.Application.InvokeOnUIThread(async () =>
7. {
8.     InitializePrinting();
9. }, false);
10. #endif
11.  

I tried the Printing APIs in a 2018.3 release of Unity using IL2PP (invoking them on the UI thread) and didn't hit the exception or run into other issues creating a new PrintDocument.

 

Looks like I got it working. I think I was attempting to create printDoc a second time.

Really appreciate your help.