On 17/01/18 04:47, Carsten Haitzler wrote:
On Tue, 16 Jan 2018 20:23:02 +0000 Peter Flynn <pe...@silmaril.ie> said:
This is (seemingly) not an Enlightenment-specific problem; it's just
that I was running E when it happened. It appears to happen with XFCE
and Cinnamon as well, but if anyone has a clue, please email me off-list.
My Dell XPS 15 plugged into a classroom projector only displays the
wallpaper background: no icons, no menus, no windows, no bryce, nothing,
just the wallpaper. I've used this classroom and projector for years
with a lot of machines, this is the first time with this laptop.
Details at https://forums.linuxmint.com/viewtopic.php?f=147&t=261862
That is truly odd. E and XFCE are quite different beasts. E draws its wallpaper
within the compositor using textures and OpenGL as part of redrawing the scene
graph (Or maybe using the CPU and shm buffers). What is and is not drawn is
controlled client-side (not in the Xserver at all). What you have is really odd.
I thought so too. I've been plugging in laptops to overheads since they
were invented, and while projectors are notorious for screwing up on
resolution and aspect ratio (and in not detecting the computer), I've
never seen one that didn't display what it was given. I can only
conclude that somehow the XPS15 is feeding only part of the display down
the wire.
Are you sure the wallpaper is set by E?
Yes, positive. I installed a completely different wallpaper in XFCE.
you haven't run other gnome, xfce or
other tools to set a background pixmap on the root window? E never sets one (it
just sets bg color to black of the root window).
I actually don't know or understand how stuff gets onto the display, and
at my time of life there are other things to do :-)
The forum indicates you have clone mode enabled which means E won't be
rendering 2 screens of content, and only one.
I'm not familiar with clone mode.
E's randr (screen setup) stuff
will just configure 2 outputs to point to the same region on the root window,
and that's it. The Xserver should configure the scanouts/CRTC's to produce a
display signal for those pixels for both outputs (LCD panel and VGA). If one
output produces different content... The logical assumption is that one output
is NOT pointing to the same region or memory. One idea might be that somehow by
pure luck it's pointing to the texture memory for the bg pixmap and they just
happen to line up perfectly... normally if this happened i'd expect it to point
to random garbage in video memory.
Interesting analysis, thank you.
Does the mouse cursor appear at all on that screen?
No, nothing but the wallpaper. When I get a chance to go back into that
room again I will remove the wallpaper first, so that E goes back to its
default black background.
And find some time to try it on other projectors...
///Peter
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