Over SSH with X11 forwarding the app does not appear: no usable Vulkan device means GTK cannot
create a swapchain, and `--renderer cairo` fixes that half only -- the plot is a GtkGLArea and asks
for its own GL context, so indirect GLX is the second wall. A virtual X server on the machine that
runs the app sidesteps both, because the GL context then lives next door to the samples.
`tools/udpscope-remote.sh` starts Xvfb on a free display, runs the app there with
`--renderer cairo`, and serves the screen through x11vnc bound to localhost only -- the SSH tunnel
is the authentication, so `-nopw` is deliberate and `-localhost` is what keeps a mistake from being
a remotely reachable screen. It prints the tunnel and viewer commands rather than assuming a
client, mentions the websockify/noVNC route for a browser, and takes the X and VNC servers with it
when the app exits. `--no-vnc` leaves just the virtual display, for another viewer; the preflight
names the install command instead of a bare "command not found".
Verified: the preflight refuses with exit 1 and the install line when x11vnc is absent; with
`--no-vnc` the app runs against the virtual display and reads `buffer allocated: 4 channels` with
no Vulkan warning and no critical, and no Xvfb is left behind when the timeout ends it. That run
also exercises what the earlier log showed by omission: nothing is enabled, so a working app
plots nothing.
The README's Limitations gains the bullet a person actually needs -- the exact warning string, that
both halves need the software preset, the script itself, and that a window which appears but stays
empty usually means no signal is enabled.
Martino Ferrari
f3f8f67a62