DoModal briefly shows IDC_WAIT, why?

Robbie Gluon 1

I'm using WTL (not that it should make a difference). In my program when the user clicks an element in the UI, I show a modal dialog. The modal dialog is derived from ATL::CDialogImpl<Dialog_Base>. I create the dialog and call DoModal(). The dialog displays when I do this. So far, so good.

The problem I have is when I call DoModal the mouse cursor changes to IDC_WAIT just for a split second (the blue circle), and sometimes a little long than split, more half a second or so. I'm not changing the mouse cursor to IDC_WAIT at all and as far as I can see neither is WTL.

Can someone explain what's going on here? Is Raymond Chen around?

Igor Tandetnik 1,106 Reputation points

2022-10-09T14:47:42.09+00:00

My guess would be, the OS changes the cursor when the program doesn't respond to WM_SETCURSOR message in a timely manner. Basically, your application hangs: you have some lengthy initialization that blocks the UI thread and prevents it from processing messages.
Robbie Gluon 1 Reputation point

2022-10-09T16:15:19.2+00:00

That sounds reasonable as an explanation, i.e. that the kernel is doing something but I'm showing a modal dialog and there's nothing in WM_INITDIALOG except setting the window to layered (WS_EX_LAYERED), setting the window position (::SetWindowPos) and enabling its parent window (::EnableWindow), so the user can click it to hide the dialog.

I'm now wondering if the issue is EnableWindow on the parent. The documentation says it "sends WM_CANCELMODE" to it. Perhaps my pattern is all wrong and the window shouldn't be modal. I'm trying to get a kind-of tool-tip behaviour for it without getting into a tangle of messages (send parent message when we become deactivated, parent destroys the dialog, etc.).
Junjie Zhu - MSFT 14,751 Reputation points Microsoft Vendor

2022-10-10T09:11:09.453+00:00

Hi @Robbie Gluon ,
Welcome to Microsoft Q&A!

Is your project Win32 Desktop Application or MFC?
Robbie Gluon 1 Reputation point

2022-10-10T19:08:09.26+00:00

Win32 Desktop Application
YujianYao-MSFT 4,271 Reputation points Microsoft Vendor

2022-10-12T08:55:57.31+00:00

Hi @Robbie Gluon ,

I tested the domodal function and it doesn't have the problem you mentioned on my computer.

I agree with @Igor Tandetnik on the cause of this problem, are there many other threads in your pc?

Could you please provide more information about your code environment if it is convenient?
Robbie Gluon 1 Reputation point

2022-10-19T13:41:43.83+00:00

Apologies for not replying to this sooner. I had to break from this to work on something else.

My env is Windows 11 (also same issue on win 10). I'm using VS 2019. I have a C++ solution and I'm using WTL as the basis of window management and msg handling.

Here's what happens: The user clicks on an element in my scene. After GetDoubleClickTime() time has passed (I have a timer ticking to check), I determine that it's OK to show the dialog as the user won't be dbl-clicking. I then ::PostMessage() to the parent window. The handler (Wm_Show_Tip) constructs and displays the dialog.

I decided to check how long everything took to execute. So, I enter the message handler and construct the dialog:

Wm_Show_Tip::Show Tip Begin 0ms
Wm_Show_Tip::Construct Dialog 0ms
Dialog::Constructor End 0ms

, I call DoModal:

Wm_Show_Tip::DoModal 0ms
Dialog::Wm_Init_Dialog Start 3ms
Dialog::Wm_Init_Dialog End 7ms

, the dialog finishes when I click away:

Wm_Show_Tip::DoModal Finishes 753ms

3ms passes between DoModal and WM_INITDIALOG, and dialog init takes 4ms. I tried this with a different dialog class, i.e. described here, just in case I'd done something dumb in my impl, and I get the same effect. The effect can be seen in this video. As my surfaces are layered, the background elements were not captured. You can see the IDC_WAIT appearing as I click elements (bottom, right).

Thanks for any insight.
YujianYao-MSFT 4,271 Reputation points Microsoft Vendor

2022-10-24T01:35:41.81+00:00

HI @Robbie Gluon ，

Have you tested this project on other computers? What kind of results did you get?