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Re: opengl render size too small in X11 window

The initial render of the OpenGL content now fills the xwindow area but if
you resize the window making it larger then the opengl content is scaled up
by more than needed and the result is the xwindow area ends up with the
bottom left corner of the expected viewing area.

If, on the other hand, you resize smaller than the opengl rendered area
shrinks faster than the amount appropriate for the change in size with the
result that the content is completely visible in the bottom left corner off
the xwindow area with blank regions to above and on the right to fill our
the xwindow area.

I can take screen shots that illustrate the problem but I don't have a way
to get them to you.


On Sun, Oct 14, 2018 at 11:01 AM Chris Marshall <devel.chm.01@xxxxxxxxx>

> Will do.
> On Sun, Oct 14, 2018 at 10:13 AM Jon Turney <jon.turney@xxxxxxxxxxxxxxxx>
> wrote:
>> On 11/10/2018 18:40, Chris Marshall wrote:
>> > I've verified that if I use the -nowgl option for the X11 server then
>> the
>> > opengl visualization is correctly rendered and sized for the containing
>> > window.
>> >
>> > On Wed, Oct 10, 2018 at 12:15 PM Chris Marshall
>> > wrote:
>> >
>> >> Dear Cygwin-
>> >>
>> >> Using cygwin X11 under windows 10 with a high dpi display (3840x2160)
>> >> laptop resulted in far too small font and widgets using -multiwindow
>> for
>> >> the XWin option.  If I set the windows setting display resolution to
>> >> 1920x1080 and following the suggestion for the ~/.Xresources file from
>> >>
>> https://stackoverflow.com/questions/42211564/cygwin-xwin-scaling-broken-when-using-windows-scaling-on-high-resolution-displa
>> >> I was able keep windows, widgets, and title/menu bars at a reasonable
>> size
>> >> for reading.
>> >>
>> >> However, when I display some OpenGL graphics content (using a FreeGLUT
>> >> window), then the visible OpenGL rendered area is about 2/3 the
>> apparent
>> >> widget area of the X11 window.  If I try the same in a non-multiwindow
>> Xwin
>> >> session then the rendered area is correct.  This problem is even worse
>> if I
>> >> try with the full screen resolution.  At the moment I think I have
>> narrowed
>> >> it down to the -multiwindow support for OpenGL contexts.
>> >>
>> >> This is with a couple of versions of the freeglut libraries with no
>> effect
>> >> and the current cygwin and cygwin X Server.
>> Interesting.  Thanks for reporting this issue.
>> I suspect this might be caused by:
>> - the X server is marked as high-dpi aware (via manifest)
>> - when using WGL, OpenGL drawing takes place in the client (to a window
>> handle retrieved from the X server)
>> - the GL client you are using is not marked as high-dpi aware (the
>> default)
>> (-wgl is only currently supported in multiwindow mode)
>> If that's the case, I think I see what is needed to fix this, but this
>> is not possible for me to test.
>> I've built an updated libGL1 with this potential fix, perhaps you can
>> try it, to see if it improves things. Install it with:
>> wget ftp://cygwin.com/pub/cygwinx/x86_64/libGL1-18.0.5-1.1.tar.xz
>> tar -C / -xvf libGL1-18.0.5-1.1.tar.xz
>> (This is built for x86_64. If you need x86 instead, please ask)
>> Reinstall the libGL1 using cygwin setup to get things back to their
>> previous state.
>> --
>> Jon Turney
>> Volunteer Cygwin/X X Server maintainer

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