add multi monitor screenshare support

README.md

@@ -61,12 +61,14 @@ A secure confirmation dialog will appear asking where the webcam stream is to be
 
 Simply run the following command in the virtual machine of the screen sharing recipient:
 
-`qubes-video-companion screenshare`
+`qubes-video-companion screenshare [screenId]`
 
 A secure confirmation dialog will appear asking where the screen to share is to be sourced from. Select any qube as the target screen, this could be a regular unprivileged qube such as `personal` or a [DisposableVM](https://www.qubes-os.org/doc/disposablevm/), or the ultimately trusted `dom0` (caution is advised to avoid information disclosure. Afterwards, confirm the operation by clicking `OK`.
 
 Note that confirmation isn't required when a VM wants to view the screen of a DisposableVM it launched itself because the parent VM already has full control over the DisposableVM.
 
+The command above will share all active monitors in a multi monitor setup per default. You can pass the screenId as optional parameter to share a specific screen only.
+
 ### Preview
 
 At this point, install and open an application such as Cheese (packaged as `cheese`) to preview the webcam or screen shared video stream. You're all set!

receiver/qubes-video-companion

@@ -9,7 +9,7 @@ set -E # Enable function inheritance of traps
 trap exit ERR
 
 usage() {
-    echo "Usage: qubes-video-companion webcam|screenshare"
+    echo "Usage: qubes-video-companion webcam|screenshare [screenId]"
 } >&2
 
 video_source="$1"
@@ -53,4 +53,8 @@ fi
 /usr/share/qubes-video-companion/receiver/setup.sh
 # Disabling buffering should lower latency and it doesn't seem to impact performance
 # Filter standard error escape characters for safe printing to the terminal from the video sender
-qrexec-client-vm --buffer-size=0 --filter-escape-chars-stderr -- dom0 "$qvc_service" /usr/share/qubes-video-companion/receiver/receiver.py
+if [ -z "$2" ]; then
+	qrexec-client-vm --buffer-size=0 --filter-escape-chars-stderr -- dom0 "$qvc_service" /usr/share/qubes-video-companion/receiver/receiver.py
+else
+	qrexec-client-vm --buffer-size=0 --filter-escape-chars-stderr -- dom0 "$qvc_service+$2" /usr/share/qubes-video-companion/receiver/receiver.py
+fi

receiver/receiver.py

@@ -4,9 +4,14 @@
 # Copyright (C) 2021 Demi Marie Obenour <[email protected]>
 # Licensed under the MIT License. See LICENSE file for details.
 
-import sys
-import struct
 import os
+import struct
+import sys
+
+import gi
+gi.require_version('Gdk', '3.0')
+from gi.repository import Gdk
+
 from typing import NoReturn
 
 def main(argv) -> NoReturn:
@@ -52,13 +57,26 @@ def read_video_parameters() -> (int, int, int):
         raise AssertionError('bug')
 
     untrusted_input = os.read(0, input_size)
+    if not untrusted_input:
+        raise RuntimeError('can not read from stream')
     if len(untrusted_input) != input_size:
         raise RuntimeError('wrong number of bytes read')
     untrusted_width, untrusted_height, untrusted_fps = s.unpack(untrusted_input)
     del untrusted_input
 
-    if untrusted_width > 4096 or untrusted_height > 4096 or untrusted_fps > 4096:
-        raise RuntimeError('excessive width, height, and/or fps')
+    screen = Gdk.Display().get_default().get_default_screen()
+    if untrusted_width > screen.width() or untrusted_height > screen.height():
+        raise RuntimeError('excessive width, height')
+
+    if untrusted_fps > 60:
+        raise RuntimeError('excessive fps')
+
+    if untrusted_width > (3840 * 3):
+        raise RuntimeError('excessive width')
+
+    if untrusted_height > (2160 * 3):
+        raise RuntimeError('excessive height')
+
     width, height, fps = untrusted_width, untrusted_height, untrusted_fps
     del untrusted_width, untrusted_height, untrusted_fps
 

sender/screenshare.py

@@ -13,10 +13,11 @@
 gi.require_version('Gdk', '3.0')
 from gi.repository import Gdk
 from service import Service
+import sys
 
 class ScreenShare(Service):
     """Screen sharing video souce class"""
-
+    _share_specific_screen = None
     def __init__(self):
         self.main(self)
 
@@ -26,10 +27,33 @@ def video_source(self) -> str:
     def icon(self) -> str:
         return 'video-display'
 
+    def get_specific_monitor(self, monitor_id):
+        amount_of_monitors = Gdk.Display().get_default().get_n_monitors()
+        if monitor_id >= amount_of_monitors:
+            return None
+
+        return Gdk.Display().get_default().get_monitor(monitor_id)
+
+    def parse_args(self):
+        import argparse
+        parser = argparse.ArgumentParser()
+        parser.add_argument('screen', type=int, nargs='?', default=None, help='id of the screen to share')
+
+        args = parser.parse_args()
+        self._share_specific_screen = args.screen
+
     def parameters(self):
-        monitor = Gdk.Display().get_default().get_monitor(0)
-        scale, geometry = monitor.get_scale_factor(), monitor.get_geometry()
-        return (scale * geometry.width, scale * geometry.height, 30)
+        if self._share_specific_screen != None:
+            monitor = self.get_specific_monitor(self._share_specific_screen)
+            if not monitor:
+                raise RuntimeError("requested screen to share does not exist")
+
+            scale, geometry = monitor.get_scale_factor(), monitor.get_geometry()
+            return (scale * geometry.width, scale * geometry.height, 30)
+
+        else:
+            screen = Gdk.Display().get_default().get_default_screen()
+            return (screen.width(), screen.height(), 30)
 
     def pipeline(self, width: int, height: int, fps: int):
         caps = ('width={0},'
@@ -39,7 +63,7 @@ def pipeline(self, width: int, height: int, fps: int):
                 'pixel-aspect-ratio=1/1,'
                 'max-framerate={2}/1,'
                 'views=1'.format(width, height, fps))
-        return [
+        args = [
             'ximagesrc',
             'use-damage=false',
             '!',
@@ -55,6 +79,19 @@ def pipeline(self, width: int, height: int, fps: int):
             '!',
             'fdsink',
         ]
+        if self._share_specific_screen != None:
+            monitor = self.get_specific_monitor(self._share_specific_screen)
+            if not monitor:
+                raise RuntimeError("requested screen to share does not exist")
+            geometry = monitor.get_geometry()
+
+            args.insert(1, "startx={}".format(geometry.x))
+            args.insert(2, "starty={}".format(geometry.y))
+            args.insert(3, "endx={}".format(geometry.x+geometry.width-1))
+            args.insert(4, "endy={}".format(geometry.y+geometry.height-1))
+
+        print(" ".join(args))
+        return args
 
 if __name__ == '__main__':
     screenshare = ScreenShare()

sender/service.py

@@ -66,6 +66,10 @@ def parameters(self):
         """
         raise NotImplementedError("Pure virtual method called!")
 
+    def parse_args(self):
+        import argparse
+        argparse.ArgumentParser().parse_args()
+
     def quit(self) -> None:
         """Close the pipeline"""
 
@@ -119,8 +123,8 @@ def start_transmission(self) -> None:
     def main(cls, self) -> NoReturn:
         """Program entry point"""
 
-        import argparse, qubesdb, os
-        argparse.ArgumentParser().parse_args()
+        import qubesdb, os
+        self.parse_args()
 
         try:
             target_domain = qubesdb.QubesDB().read('/name').decode('ascii', 'strict')