lyx and QT5 blank windows

[Marco Atzeri]

Am 26.04.2020 um 15:54 schrieb Yaakov Selkowitz:
> 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 Good idea, since Qt4 is obsolete and unmaintained (both upstream and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).

side effect of the python 2 to 3 transfer

but is is still QT4 oriented
https://wiki.lyx.org/LyX/Dependecies

"LyX 2.3.x series need Qt >= 4.8, widely tested with 4.8. For Qt 5 we 
suggest Qt 5.6 (widely tested). "

>> 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.

thanks.
With Cygserver those are gone.

>> 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
> 

Thanks.

In the meantime I found a solution.

Removed the old .startxwinrc and the problem is gone.
Maybe something changed in one of the last release of X
that make the old file not anymore compatible.

Test version with QT5 and python 3 (3.6 for the time being) on the way

Regards
Marco