Re: qt4 and today screen problem: solved!

I found a workaround that seems to solve the problem for all the cases
I could find.
I feel that the hack could be reduced even more, but I am happy enough
with it now. Maybe someone can give any hints on that.

> The window in question is a parentless window,
> with style set to WS_VISIBLE (0x80000000) and EX_STYLE to 0.
> 
> I read somewhere about a today screen problem if your window is
> parentless and has WS_POPUP style it will always show above the
today
> screen.
> Could this be related?
I guess it was :)

I was setting the style to WS_VISIBLE (0x80000000) and EX_STYLE to 0,
AFTER the creation. My hunch is that the today screen bug trigger when
the today screen is the _OWNER_ window. So the WS_POPUP style must be
removed at creation time of the window.

Here is the workaround:
When I create the window, if is is parentless and is going to have 
WS_POPUP style set, I remove it, and set it after creation.
After that, I call SetWindowLong set the correct style.
The I stumble something unexpected. In this case the style is not
updated until the window is activated a second time. I tried sending a
WM_NCACTIVATE/FALSE, to force it to be updated, and it worked, but
invalidates the workaround/triggers the original bug. So, no can do.

The solution I am using now, is when I am going to show the window,
if it is parentless, show it, show another window on top, and
immediatly closed this new window. This has the effect of triggering a
WM_ACTIVATE cycle, that correctly updates the style and gets rid of
the today screen bug! Hurray! I am so happy.
This way is better than just hiding the window and showing it again,
cause that introduces visible flicker.

creation: --------------------

...

int prevstyle = style;
if (!parentw)
  style &= ~WS_POPUP;

const WCHAR *cname = (const WCHAR *)windowClassName.utf16();
id = CreateWindowEx(exsty, cname, ttitle, style, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, parentw, 0, appinst, 0);
if (style != prevstyle)
{
 SetWindowLong( id, GWL_STYLE, prevstyle );
 UpdateWindow(id);
}

...

showing: --------------------

...
ShowWindow(q->winId(), sm);
if (!parentw)
{
// second part of create_sys hack for parentless WS_POPUP windows
// setting style after creating window only takes effect without
// the today screen problem after a WM_ACTIVATE false, 
// followed by a WM_ACTIVATE true
  static HWND id = 0;
  extern bool qt_ignore_sys_events;
  qt_ignore_sys_events = true;
  if (!id)
  {
	HINSTANCE appinst  = qWinAppInst();
	WNDCLASS wc = {0};
	wc.lpfnWndProc        = DefWindowProc;
	wc.hInstance        = appinst;
	wc.lpszClassName= L"QT_HACK_WINDOW";
	RegisterClass(&wc);
	id = CreateWindowEx(
	0, wc.lpszClassName, 0, 
	WS_VISIBLE | WS_EX_TOOLWINDOW, 0, 0, 0, 0, 
	NULL, 0, appinst, 0);
	if (!id)
	  qDebug("hack window creation failed");
  }
  SetForegroundWindow(id);
  ShowWindow(id, SW_HIDE);
  qt_ignore_sys_events = false;
}
SetForegroundWindow(q->winId());
UpdateWindow(q->winId());

...


P.S.
If you read to this point it means my mails are still not long enough
to be boring, or are they? :)


Pedro Alves







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