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# Size/move loop and delay in DefWindowProc

## 21 posts in this topic

I'm trying to start a timer when the user starts to drag the window, so I can render a frame on the WM_TIMER message, to prevent the stall that happens when the user drags the window. I added some logging and found that DefWindowProc() for WM_SYSCOMMAND (With a wParam of 0xf012, which doesn't seem to be a recognised SC_* value) and WM_NCLBUTTONDOWN takes a considerable time to return (Over 500ms). With some more logging, it seems that WM_NCLBUTTONDOWN comes first, and calling DefWindowProc causes a WM_SYSCOMMAND message to be sent (So it's recursing into the window proc, hence the delay on both messages). The call stack at the time if I break with F12 isn't very exciting:
ntdll.dll!_KiFastSystemCallRet@0()
user32.dll!_NtUserMessageCall@28()  + 0xc bytes
user32.dll!_RealDefWindowProcWorker@20()  - 0x79d6 bytes
user32.dll!_RealDefWindowProcW@16()  + 0x27 bytes
uxtheme.dll!DoMsgDefault()  + 0x29 bytes
uxtheme.dll!OnDwpSysCommand()  + 0x29 bytes
uxtheme.dll!_ThemeDefWindowProc()  + 0x61a8 bytes
uxtheme.dll!_ThemeDefWindowProcW@16()  + 0x18 bytes
user32.dll!_DefWindowProcW@16()  + 0x815 bytes
>	Tutorial02.exe!D3DWindow::WndProc(unsigned int uMsg=274, unsigned int wParam=61458, long lParam=5636612)  Line 227 + 0x1b bytes	C++
Tutorial02.exe!D3DWindow::StaticWndProc(HWND__ * hWnd=0x000a06fa, unsigned int uMsg=274, unsigned int wParam=61458, long lParam=5636612)  Line 169 + 0x1a bytes	C++
user32.dll!_InternalCallWinProc@20()  + 0x23 bytes
user32.dll!_UserCallWinProcCheckWow@32()  - 0xddcf bytes
user32.dll!_DispatchClientMessage@20()  + 0x4b bytes
user32.dll!___fnDWORD@4()  + 0x24 bytes
ntdll.dll!_KiUserCallbackDispatcher@12()  + 0x2e bytes
user32.dll!_NtUserMessageCall@28()  + 0xc bytes
user32.dll!_RealDefWindowProcWorker@20()  - 0x79d6 bytes
user32.dll!_RealDefWindowProcW@16()  + 0x27 bytes
uxtheme.dll!DoMsgDefault()  + 0x29 bytes
uxtheme.dll!OnDwpNcLButtonDown()  + 0x32 bytes
uxtheme.dll!_ThemeDefWindowProc()  + 0x61a8 bytes
uxtheme.dll!_ThemeDefWindowProcW@16()  + 0x18 bytes
user32.dll!_DefWindowProcW@16()  + 0x815 bytes
Tutorial02.exe!D3DWindow::WndProc(unsigned int uMsg=161, unsigned int wParam=2, long lParam=5636612)  Line 227 + 0x1b bytes	C++
Tutorial02.exe!D3DWindow::StaticWndProc(HWND__ * hWnd=0x000a06fa, unsigned int uMsg=161, unsigned int wParam=2, long lParam=5636612)  Line 169 + 0x1a bytes	C++
user32.dll!_InternalCallWinProc@20()  + 0x23 bytes
user32.dll!_UserCallWinProcCheckWow@32()  + 0xb3 bytes
user32.dll!_DispatchMessageWorker@8()  + 0xe6 bytes
user32.dll!_DispatchMessageW@4()  + 0xf bytes
Tutorial02.exe!WinMain(HINSTANCE__ * hInstance=0x009f0000, HINSTANCE__ * __formal=0x00000000, HINSTANCE__ * __formal=0x00000000, HINSTANCE__ * __formal=0x00000000)  Line 22 + 0xf bytes	C++
Tutorial02.exe!__tmainCRTStartup()  Line 578 + 0x35 bytes	C
Tutorial02.exe!WinMainCRTStartup()  Line 403	C


Obviously returning 0 from WM_NCLBUTTONDOWN doesn't cause WM_SYSCOMMAND to be sent, and no delay, but it also prevents the window from being moved. So, does anyone know what's going on here and if there's any way of stopping it? Cheers, Steve
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How complex are your renders and what kind of delay are you putting on your timer? If you have a relatively simple render and a relatively low update frequency, then you might want to just start the timer up when the window is created and let it run.
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Quote:
 Original post by SiCraneHow complex are your renders and what kind of delay are you putting on your timer? If you have a relatively simple render and a relatively low update frequency, then you might want to just start the timer up when the window is created and let it run.
Currently the render is very basic (A single triangle), and the timer is set to 0ms, so just "as fast as possible".

However, this is for a tutorial / article on D3D rendering, and I'd like to do things as "correctly" as possible, even if it means leaving the 500ms lag.

Also, this is D3D (In case that's not obvious from the call stack function names [smile]), so running rendering in another thread is out of the question.

EDIT: And I'm curious about what exactly is going on under the hood here.

[Edited by - Evil Steve on January 14, 2009 3:33:36 PM]
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What kind of stall are you referring to? To my knowledge the window will NEVER update while it's being dragged. Your program will keep executing though. Have you considered throwing your timer code into the main loop instead of relying on your window procedure? I recommend QueryPerformanceCounter() if you do. 64-bit calculations... Nummy. Also, what is your definition of "correctly?"
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There are some other things that cause about a 500ms stall, such as grabbing a window title bar. In fact, now that I think about it, grabbing a window title bar causes WM_SYSCOMMAND with a wparam value of 0xf012 which is in fact (SC_MOVE + HTCAPTION).

EDIT: You may find Spy++ will give you useful information about what messages are occuring. To me it is worlds easier than a call stack for windows message monitoring.
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This is a guess, but I'm thinking DefWindowProc is waiting to see whether you're about to double-click or not. Try setting your double-click delay really slow or really fast to see if that affects things.

If that's the case, then there's probably not a lot you can do about it (but maybe make a note in your tutorial or something [smile]).
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Thanks for the replies.

Quote:
 Original post by kittycat768What kind of stall are you referring to? To my knowledge the window will NEVER update while it's being dragged. Your program will keep executing though. Have you considered throwing your timer code into the main loop instead of relying on your window procedure? I recommend QueryPerformanceCounter() if you do. 64-bit calculations... Nummy. Also, what is your definition of "correctly?"
For the stall, DefWindowProc doesn't return for over 500ms. It's as if it's an extremely expensive function call. Putting a timer in the main loop wouldn't help, and for now GetTickCount() is accurate enough (You don't need to render at full speed when the user is moving the window).
My definition of "correctly" is to render in the main loop, not from a timer handler - the timer handler isn't called all that frequently as far as I'm aware.

Quote:
 Original post by lordikonThere are some other things that cause about a 500ms stall, such as grabbing a window title bar. In fact, now that I think about it, grabbing a window title bar causes WM_SYSCOMMAND with a wparam value of 0xf012 which is in fact (SC_MOVE + HTCAPTION).EDIT: You may find Spy++ will give you useful information about what messages are occuring. To me it is worlds easier than a call stack for windows message monitoring.
Ah, I didn't notice that the wParam can include HTCAPTION, thanks. It's the WM_SYSCOMMAND handling in DefWindowProc that causes the 500ms stall - that's what I'm trying to fix or work around.

Quote:
 Original post by CodekaThis is a guess, but I'm thinking DefWindowProc is waiting to see whether you're about to double-click or not. Try setting your double-click delay really slow or really fast to see if that affects things.If that's the case, then there's probably not a lot you can do about it (but maybe make a note in your tutorial or something [smile]).
I don't think that's it, I always have my double click delay set to as fast as possible, and that should be less than 500ms. I'll give that a try when I get a chance though.

Cheers,
Steve
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Quote:
 Original post by Evil SteveMy definition of "correctly" is to render in the main loop, not from a timer handler - the timer handler isn't called all that frequently as far as I'm aware.

You could try starting a timer at window creation and calling InvalidateRect() in the timer handler, which will cause WM_PAINT messages to be generated even when your window is being dragged.
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Could this be because you've got a Direct3d device open inside the window?

Does that stall also happen without D3D? It might be because you're actually losing the device.

If it is because of D3D, could it be the debug runtimes?
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Quote:
 Original post by CodekaThis is a guess, but I'm thinking DefWindowProc is waiting to see whether you're about to double-click or not. Try setting your double-click delay really slow or really fast to see if that affects things.
Setting my double click speed to extremely slow still takes the same time for DefWindowProc to return, so that doesn't seem to be related.

Quote:
 Original post by SiCraneYou could try starting a timer at window creation and calling InvalidateRect() in the timer handler, which will cause WM_PAINT messages to be generated even when your window is being dragged.
Hmm, it's possible - but still seems a bit ugly to me. This is beginning to look like the only option though...

Quote:
 Original post by EndurionCould this be because you've got a Direct3d device open inside the window?
Disabling D3D completely (Commenting out any reference to any D3D interface) still yields the same problem.
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This problem happens even if you create a timer at window-creation. I've always wondered why..
It doesn't happen if you start dragging the window right away, moving the mouse already when you click. It also pauses if you hold down the button on the minimize button for example. I think all such things are handled in some loop that doesn't return, except for that once the window starts moving it returns to allow for interactive moving.
Don't know why it waits 500 ms before returning unless the mouse moves.. the reply about double-clicking sounds plausible to me..
It also freezes if you hold down the right mouse-button in the title bar.
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Quote:
 Original post by Evil SteveHmm, it's possible - but still seems a bit ugly to me. This is beginning to look like the only option though...

I create the timer the first time WM_MOVING is reached, and remove the timer when WM_EXITSIZEMOVE is reached. This doesn't help with the delay though. There is about a 500ms delay between the time the user clicks the title bar and I receive SC_MOVE + HTCAPTION. During this time the window stops updating.
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Quote:
 Original post by lordikonI create the timer the first time WM_MOVING is reached, and remove the timer when WM_EXITSIZEMOVE is reached. This doesn't help with the delay though. There is about a 500ms delay between the time the user clicks the title bar and I receive SC_MOVE + HTCAPTION. During this time the window stops updating.
Yep, it's that 500ms delay that I'm trying to avoid.
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I'm also fairly interested in this solution. I wish I could help, but after some research I found no answers either.
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So, it appears you've been having this problem for awhile. :D

http://www.gamedev.net/community/forums/topic.asp?topic_id=440341
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Quote:
 Original post by lordikonSo, it appears you've been having this problem for awhile. :Dhttp://www.gamedev.net/community/forums/topic.asp?topic_id=440341
Yeah, I found that post while Googling, but decided not to necro the thread [smile]
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Here is a quick workaround. Note that this has the little quirk of setting the cursor position to the middle of the window's caption. Also, if the app has other windows and he starts dragging them, the problem remains. Also, the delay will remain if the window is sizable and the user [EDIT: referred to in the previous sentence as "he"] clicks on the borders to resize it. Also, this will effectively disable double-clicking the title bar to maximize the window. Plus possibly a few more things I haven't thought about yet.

case WM_NCLBUTTONDOWN:		if( SendMessage( hWnd, WM_NCHITTEST, wParam, lParam ) == HTCAPTION )		{			SetTimer( hWnd, 1000, 0, NULL );			SendMessage( hWnd, WM_SYSCOMMAND, SC_MOVE, 0 );			return 0;		}		break;	case WM_TIMER:		Render();		break;	case WM_EXITSIZEMOVE:		KillTimer( hWnd, 1000 );		break;

But personally I would recommend against messing with this because, well, you're just nitpicking one of Windows' insignificant quirks. That's not patriotic!

[Edited by - hikikomori-san on January 15, 2009 10:47:56 AM]
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They mention the same delay problem.
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Quote:
 Original post by lordikonJust found this: http://developer.popcap.com/forums/showthread.php?p=19636They mention the same delay problem.
Yes, I've been through Google. I've found plenty of reports of the problems, but no solutions.

Quote:
 Original post by hikikomori-sanHere is a quick workaround. Note that this has the little quirk of setting the cursor position to the middle of the window's caption. Also, if the app has other windows and he starts dragging them, the problem remains. Also, the delay will remain if the window is sizable and the user [EDIT: referred to in the previous sentence as "he"] clicks on the borders to resize it. Also, this will effectively disable double-clicking the title bar to maximize the window. Plus possibly a few more things I haven't thought about yet.
Hmm, I'll give that a go later tonight, thanks.
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Quote:
 Original post by hikikomori-sanHere is a quick workaround. Note that this has the little quirk of setting the cursor position to the middle of the window's caption. Also, if the app has other windows and he starts dragging them, the problem remains. Also, the delay will remain if the window is sizable and the user [EDIT: referred to in the previous sentence as "he"] clicks on the borders to resize it. Also, this will effectively disable double-clicking the title bar to maximize the window. Plus possibly a few more things I haven't thought about yet.
This seems to work pretty well, with a bit of an ajustment:
LRESULT D3DWindow::WndProc(UINT uMsg, WPARAM wParam, LPARAM lParam){static bool sbMoving = false;static POINT sptOffset;	switch(uMsg)	{	case WM_NCLBUTTONDOWN:		if(SendMessage(m_hWnd, WM_NCHITTEST, wParam, lParam) == HTCAPTION)		{			POINT ptCursor;			RECT rcWnd;			GetWindowRect(m_hWnd, &rcWnd);			GetCursorPos(&ptCursor);			sptOffset.x = ptCursor.x - rcWnd.left;			sptOffset.y = ptCursor.y - rcWnd.top;			SetCapture(m_hWnd);			sbMoving = true;			return 0;		}		break;	case WM_NCLBUTTONUP:	case WM_LBUTTONUP:		sbMoving = false;		ReleaseCapture();		break;	case WM_MOUSEMOVE:	case WM_NCMOUSEMOVE:		if(sbMoving)		{			POINT ptCursor;			RECT rcWnd;			GetWindowRect(m_hWnd, &rcWnd);			GetCursorPos(&ptCursor);			SetWindowPos(m_hWnd, NULL, rcWnd.left+(ptCursor.x-(rcWnd.left+sptOffset.x)),				rcWnd.top+(ptCursor.y-(rcWnd.top+sptOffset.y)), 0, 0, SWP_NOZORDER | SWP_NOSIZE);		}		break;	}	return DefWindowProc(m_hWnd, uMsg, wParam, lParam);}

I dread to think what horrible bugs this will cause though, so I think I'm just going to use the method with the 500ms delay for this, and add the above method as an alternative.
Another issue is that the user can still access the system menu of the window (Which will cause a stall), and select "Move" from there - which will stall. The second issue can be fixed with the timer as before, but probably not the stall when selecting the system menu.

Thanks for all the replies,
Steve
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It's down to a 500ms wait on an event when there are no mouse, keyboard, or sync messages in the queue. The event seems to be signalled when there are input messages available. There's also lots of resource locking which is mostly block-until-available so 500ms would be a lower bound to the stall. Lots of calls to user mode as well for hooking purposes so there's a few context switches to account for too.

The "highlights" from WM_SYSCOMMAND to WM_MOVING:
xxxSysCommand-    Calls some hook back in UM    xxxIsDragging-	  GetKeyState(VK_LBUTTON)-		Just checks some bits, nothing heavy	  Sets mouse capture to window-		Locks and unlocks the window		Checks if the thread's impersonation token or the process token is restricted		Checks user has WINSTA_WRITEATTRIBUTES permission on the Window Station	  xxxInternalGetMessage (..., WM_MOUSEFIRST, WM_XBUTTONDBLCLK..)-if any mouse action		Calls mouse hooks -> back to UM		Removes WM_LBUTTONUP from Queue		Calls mouse hooks again -> back to UM		seems it loops around couple of timesotherwise	  	Exits without doing anything of note	  xxxInternalGetMessage(..., WM_QUEUESYNC, WM_QUEUESYNC)	  if no message-	  xxxInternalGetMessage(..., WM_KEYFIRST, WM_KEYLAST)	  if no message-	  xxxSleepThread(7, 500, 1)		KeClearEvent()		KeWaitForSingleObject(ClearedEvent, -500ms) // seems to be for inputend if	  Releases mouse capture on window-	  	Locks and unlocks the window again	  	Puts WM_MOUSEMOVE in message queue	  	Calls window proc with WM_CAPTURECHANGED (0x0215)        returns whether the message x/y pos was within a specified rect (if there was a message)if dragging    xxxSetWindowPos(PWND, 0, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE) -	  BeginDeferWindowPos(1)	  DeferWindowPos()	  EndDeferWindowPosEx()		Z-Order checking stuff for a few windows		Call app WndProc with WM_WINDOWPOSCHANGING		Updates the previous top most window if there was one		Locks screen and blits the valid bits		Unlocks the screen		Sends any WM_WINDOWPOSCHANGED messages		returns          not checked beyond here for this case	  returnsend if     xxxMoveSize-	   Clips cursor to area	   Call app WndProc with WM_GETMINMAXINFO	   Draw the drag rectange-		SetWindowPos(PVOID, 0, x, y, width, height, (SWP_NOOWNERZORDER | SWP_NOACTIVATE | SWP_NOZORDER))-			Locks screen and blits the valid bits to the new pos			Unlocks the screen		Updates relevant Windows	   Fakes a mouse move	   Call app WndProc with WM_ENTERSIZEMOVE	   Locks Capture Window	   Show Cursor	   GetMessage(wnd, no filter)-		Scan's system queue for all messages-		   GetNextSysMessage-			WM_MOUSEMOVE posted (prob due to fake move above)		Mouse hooks called		WM_MOUSEMOVE consumed (deleted from queue)		Hooks called again		Updates drag rect-			Calls WndProc with WM_MOVING			Redraws the rect		Wait for messages
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Hello all,

I know this is a very late reply but I felt I might be able to help people searching for answers to this question by adding some information.
What happens in the 'stall' is that DefWindowProc takes over complete control. You enter DefWindowProc and it doesn't return until the move is completed.
During that time, DefWindowProc will send a lot of WM_* messages to your own window procedure (including move updates), one important one being WM_PAINT (and I'm guessing only if your system settings are such that the windows are drawn during move and resize operations). So, you can draw and therefore update your window during the stalls by responding to WM_PAINT with a scene draw.
The bad news is that all your regular game code, starting with your message pump and ending with the normal process & draw loops, don't get called during the entire operation.
Testing with a couple of other applications, I think I may have found the one compelling reason for applications to supply their own customised title bar with system menu: so as to avoid DefWindowProc hanging on non-client messages (NC_* window messages).
It seems then that the solution is either to remove all the non-client regions from your window (by setting the appropriate window styles) and implementing your own move/resize and title bar.
Or, you somehow use multi-threading to keep the core going and the window updated; somehow having your gui be pretty much a stub thread while the 'real' thread does all the work (not sure how easy this is to do...).

Hopefully, this can still help someone.
Best Regards,
MicroVirus
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