Re: lyx and QT5 blank windows

[Yaakov Selkowitz <yselkowitz@cygwin.com>]

On Sun, 2020-04-26 at 11:15 +0200, Marco Atzeri via Cygwin wrote:
> I am trying to rebuild lyx with QT5 enabled instead of QT4.

Good idea, since Qt4 is obsolete and unmaintained (both upstream and
downstream).

> The build is fine and it seems to start fine, but opening new windows 
> like "open file" only produces a blank and black window.
> 
> At running I see only this output, that is not clear if it is related
> 
> QXcbShmImage: shmget() failed (88: Function not implemented) for size 
> 1407600 (690x510)
> QXcbShmImage: shmget() failed (88: Function not implemented) for size 
> 518976 (318x408)
> Gtk-Message: GtkDialog mapped without a transient parent. This is 
> discouraged.
> QXcbShmImage: shmget() failed (88: Function not implemented) for size 
> 12000 (100x30)

Do you have cygserver running, and was it started before the X server? 
This is a requirement for the MIT-SHM extension, otherwise you need to
set QT_X11_NO_MITSHM=1 in your environment.

> and at build time there is a new warning coming from the compiler
> 
> /usr/include/qt5/QtGui/qtransform.h: In member function ‘QTransform& 
> QTransform::operator=(QTransform&&)’:
> /usr/include/qt5/QtGui/qtransform.h:81:46: warning: ‘void* memcpy(void*, 
> const void*, size_t)’ writing to an object of type ‘class QTransform’ 
> with no trivial copy-assignment; use copy-assignment or 
> copy-initialization instead [-Wclass-memaccess]
>     81 |     { memcpy(this, &other, sizeof(QTransform)); return *this; }
>        |                                              ^

I think this can be ignored for now, and will likely be fixed by a
future update to qt5.

--
Yaakov