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Prevent WPF window redrawduring resizing


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#1 BlackJoker   Members   -  Reputation: 549

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Posted 29 December 2013 - 03:33 PM

I have the following situation:

 

I use my WPF window in C++/CLI project of my game engine based on DirectX 11.

 

And my problem is when I resize a window, it always show a window background for a few milliseconds.

 I want to get rid of this behavior and don`t let window to redraw itself during resizing.

 

Does anyone faced such issue?

How I can do this in WPF window?

 

 

I tried to use SetClassLongPtr() for this puprose, but I dont know which parameters I should pass to make what i want.


Edited by BlackJoker, 29 December 2013 - 05:39 PM.


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#2 BlackJoker   Members   -  Reputation: 549

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Posted 31 December 2013 - 06:26 AM

Is it possible to make that WPF window not redraw itself during resizing?



#3 Erik Rufelt   Crossbones+   -  Reputation: 3538

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Posted 01 January 2014 - 08:51 AM

If you want to try SetClassLongPtr, check the docs here: http://msdn.microsoft.com/en-us/library/windows/desktop/ms633589%28v=vs.85%29.aspx

Use GCLP_HBRBACKGROUND, or simply -10 as it's defined as for the index and NULL for the new value, in order to remove the background brush. I'm not sure if that will be enough but it's worth a shot. Otherwise try overriding the WndProc with GWLP_WNDPROC and SetWindowLongPtr and simply return non-zero if the messages is WM_ERASEBKGND or otherwise CallWindowProc() on the old value (returned from SetWindowLongPtr).

 

I'm not certain how WPF works but it should be doable.



#4 Erik Rufelt   Crossbones+   -  Reputation: 3538

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Posted 01 January 2014 - 08:54 AM

The obvious choice if possible is ofcourse to use WPF window descriptions that make the background transparent in the first-place. Try something like this if it works: http://stackoverflow.com/questions/8094957/transparent-background-goes-black-in-wpf or Google for similar ones.



#5 BlackJoker   Members   -  Reputation: 549

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Posted 01 January 2014 - 04:24 PM

I add a hook to the window to make possible using of WndProc:

void ManagedEngine::OnSourceInitialized(System::Object ^sender, System::EventArgs ^e)
{
	HwndSource^ hwndSource = (HwndSource^)HwndSource::FromVisual((Window^)sender);
	hwndSource->AddHook(gcnew HwndSourceHook(WinDowProc));
}

IntPtr ManagedEngine::WinDowProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, bool% handeled)
{
	//Console::WriteLine(String::Format("Зашёл в цикл обработки оконных сообщений {0}", msg));
	//Keyboard::instance().handleMsg((HWND)hwnd.ToPointer(), msg, (WPARAM)wParam.ToPointer(), (LPARAM)lParam.ToPointer());
	/*return (IntPtr)DefWindowProc((HWND)hwnd.ToPointer(), msg, (WPARAM)wParam.ToPointer(), (LPARAM)lParam.ToPointer());*/
	switch (msg)
	{
	

	case WM_ERASEBKGND:
		return (IntPtr)1;
	}
	

	return IntPtr::Zero;
}

SetClassLongPtr seems to do nothing with parameters you wrote:

SetClassLongPtr(WPFHwnd, -10, NULL);

SetWIndowLongPtr with these parameters lead to appear completely white window, which cannot be even clicked:

SetWindowLongPtr(WPFHwnd, -16, NULL);

Could you please give me the cue how to make with little "hook" correctly?

 

P.S. adding transparency make the window completely invisible, so I cannot see it at all. This is not that I want to achieve.



#6 Erik Rufelt   Crossbones+   -  Reputation: 3538

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Posted 01 January 2014 - 07:19 PM

Try setting handled = true on WM_ERASEBKGND also.



#7 Erik Rufelt   Crossbones+   -  Reputation: 3538

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Posted 01 January 2014 - 07:21 PM

If you were to use SetWindowLongPtr then you should not pass NULL to it, that is only for the class-background. SetWindowLongPtr is used in the same way as AddHook, so you must pass a function address, and then save the return-value and call it with CallWindowProc for all messages except for WM_ERASEBKGND. If the hook works then you don't need that.



#8 BlackJoker   Members   -  Reputation: 549

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Posted 02 January 2014 - 01:24 AM

Hook works, but not for WM_ERASEBKGND. Seems it just ignore handled = true;



switch (msg)
	{
	case WM_ERASEBKGND:
		handeled = true;
		Console::WriteLine(handeled);
		break;
	}

Still white background visible during resizing. I cannot understand why!


Edited by BlackJoker, 02 January 2014 - 01:24 AM.


#9 Erik Rufelt   Crossbones+   -  Reputation: 3538

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Posted 02 January 2014 - 09:02 AM

I can't help but feel this should be settable in XAML or something. I don't know, and since no one else answered for several days maybe try another forum with WPF-people, or ask again after the holidays when people are back.

 

 

If you want to hack it with SetWindowLongPtr it works something like this (pseudo-code,):

WNDPROC oldWndProc = NULL;

static LRESULT CALLBACK MyWndProc(...) {
   if(msg == WM_ERASEBKGND)
      return 1;
   else
      return CallWindowProc(oldWndProc, hWnd, msg, wParam, lParam);
}

...

myOverride() {
    LongPtr result = SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LongPtr)MyWndProc);
    oldWndProc = (WNDPROC)result;
}

I would also try Googling for D3D in WPF window flicker. There are several results for people trying to do this. There seems to be an easier way to replace the Wnd-proc than using SetWindowLongPtr: http://msdn.microsoft.com/en-us/library/system.windows.forms.control.wndproc%28v=vs.110%29.aspx

 

(Maybe you should also override WM_PAINT and validate the window so it doesn't attempt to redraw again. If WPF is at all meant to be used with D3D then there should be built-in ways do do this, such as a specialized D3D image control or something so you don't have to hack it like this).


Edited by Erik Rufelt, 02 January 2014 - 09:05 AM.


#10 BlackJoker   Members   -  Reputation: 549

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Posted 02 January 2014 - 11:06 AM

Ok, thank for help anyway. 

Question is still open. If someone can say how to make background to drawing during resizing, it would be perfect.






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