Allow monitor choice

If more than one monitor is found on the target, an interactive dialog
will be prompted to the user to choose from, displaying monitor name
(port) and resolution and geometry for better identification. The
monitor can be enforced by the target by environment variable.

Fixes: QubesOS/qubes-issues#9275

doc/qubes-video-companion.rst

@@ -20,6 +20,10 @@ The project emphasizes correctness and security all the while also sporting supe
 
 OPTIONS
 =======
+resolution
+    The video resolution to stream and receive video in. The format is [WIDTHxHEIGHTxFPS], meaning resolution is optional. If you set the environment variable "QVC_MONITOR" in the target, that monitor is going to be preferred and if not found, will fallback to the primary monitor. Example: "1920x1080x60"
+
+
 video_source
     The video source to stream and receive video from. Either "webcam" or "screenshare".
 

qubes-rpc/services/qvc.ScreenShare

@@ -1,7 +1,31 @@
 #!/bin/sh --
-
 # Copyright (C) 2021 Elliot Killick <[email protected]>
 # Copyright (C) 2021 Demi Marie Obenour <[email protected]>
 # Licensed under the MIT License. See LICENSE file for details.
+
+set -eu
+
+## DISPLAY variable used by: xrandr, zenity
 export DISPLAY=:0
+
+true "${XDG_RUNTIME_DIR:="/run/user/$(id -u)"}"
+true "${DBUS_SESSION_BUS_ADDRESS="unix:path=${XDG_RUNTIME_DIR}/bus"}"
+monitors="$(xrandr --listactivemonitors \
+            | awk '/^ [0-9]+: \+/ { print "FALSE", $4, $3 }')"
+monitor_count="$(echo "${monitors}" | wc -l)"
+monitor_longest_line="$(echo "${monitors}" | wc -L)"
+dialog_height="$((monitor_count*50+60))"
+dialog_width="$((monitor_longest_line*10))"
+if test "${monitor_count}" -gt 1; then
+  # shellcheck disable=SC2086
+  QVC_MONITOR="$(zenity --list --radiolist \
+    --height="${dialog_height}" --width="${dialog_width}" \
+    --column "ID" --column "Name" --column "Resolution" \
+    --title "Screen share" \
+    --text "Select monitor to present to qube ${QREXEC_REMOTE_DOMAIN}" \
+    ${monitors})"
+fi
+true "${QVC_MONITOR:=}"
+
+export XDG_RUNTIME_DIR DBUS_SESSION_BUS_ADDRESS QVC_MONITOR
 exec python3 -- /usr/share/qubes-video-companion/sender/screenshare.py

qubes-rpc/services/qvc.Webcam

@@ -1,7 +1,9 @@
 #!/bin/sh --
-
 # Copyright (C) 2021 Elliot Killick <[email protected]>
 # Copyright (C) 2021 Demi Marie Obenour <[email protected]>
 # Licensed under the MIT License. See LICENSE file for details.
-export DISPLAY=:0
-exec python3 -- /usr/share/qubes-video-companion/sender/webcam.py ${1:+"$1"}
+set -eu
+true "${XDG_RUNTIME_DIR:="/run/user/$(id -u)"}"
+true "${DBUS_SESSION_BUS_ADDRESS:="unix:path=${XDG_RUNTIME_DIR}/bus"}"
+export DISPLAY=:0 XDG_RUNTIME_DIR DBUS_SESSION_BUS_ADDRESS
+exec python3 -- /usr/share/qubes-video-companion/sender/webcam.py "${1:+"$1"}"

receiver/qubes-video-companion

@@ -12,7 +12,8 @@ unset GETOPT_COMPATIBLE
 name=${0##*/}
 
 usage() {
-    printf '%s: Usage: qubes-video-companion [--resolution=WIDTHxHEIGHTxFPS] [--] webcam|screenshare [destination qube]\n' "$name"
+    echo "Usage: $name [--resolution=[WIDTHxHEIGHTxFPS]] [--] webcam|screenshare [destination qube]" >&2
+    echo "Resolution example: 1920x1080x60"
     exit "$1"
 }
 
@@ -23,14 +24,14 @@ while :; do
     case $1 in
         -r|--resolution)
             if [[ -z "$2" ]]; then
-                printf '%s: Empty resolution argument\n' "$name"
-                usage 0
-            fi >&2
+                echo "$name: Empty resolution argument" >&2
+                usage 1
+            fi
             resolution=${2//@/+}
             resolution=${resolution//x/+}
             shift 2
             ;;
-        --help) usage 0;;
+        -h|--help) usage 0;;
         --) shift; break;;
         *) exit 1;; # cannot happen
     esac
@@ -71,7 +72,7 @@ if ! [ -f "$qvc_lock_file" ]; then
     trap exit_clean EXIT
     sudo touch "$qvc_lock_file"
 else
-    echo "Qubes Video Companion is already running! Please stop the previous session before starting a new one." >&2
+    echo "Qubes Video Companion is already running! Please stop the previous session before starting a new one. If you think this is an error, remove the lockfile $qvc_lock_file" >&2
     exit 1
 fi
 

sender/screenshare.py

@@ -10,6 +10,7 @@
 # pylint: disable=wrong-import-position
 
 import gi
+import os
 
 gi.require_version("Gdk", "3.0")
 from gi.repository import Gdk
@@ -30,15 +31,24 @@ def icon(self) -> str:
         return "video-display"
 
     def parameters(self) -> Tuple[int, int, int]:
-        monitor = Gdk.Display().get_default().get_monitor(0).get_geometry()
+        display = Gdk.Display().get_default()
+        monitor_count = display.get_n_monitors()
+        monitor_wanted = os.environ["QVC_MONITOR"]
+        ## If wanted monitor is not found, use the primary monitor (0).
+        monitor_index = 0
+        for m in range(monitor_count):
+            if display.get_monitor(m).get_model() == monitor_wanted:
+                monitor_index = m
+                break
+        geometry = display.get_monitor(monitor_index).get_geometry()
         screen = Gdk.Screen().get_default()
         kwargs = {
-            "crop_t": monitor.y,
-            "crop_l": monitor.x,
-            "crop_r": screen.width() - monitor.x - monitor.width,
-            "crop_b": screen.height() - monitor.y - monitor.height,
+            "crop_t": geometry.y,
+            "crop_l": geometry.x,
+            "crop_r": screen.width()  - geometry.x - geometry.width,
+            "crop_b": screen.height() - geometry.y - geometry.height,
         }
-        return (monitor.width, monitor.height, 30, kwargs)
+        return (geometry.width, geometry.height, 30, kwargs)
 
     def pipeline(self, width: int, height: int, fps: int,
                  **kwargs) -> List[str]: