Add resolution settings to QCV attachment

To set resolution for use by the QVC, set the feature
device-qvc-resolution in the backend for QVC; the feature should
contain a space-delimited list of key=value pairs, where
key is the device id (see features for attach with mic to compare)
and value is the resolution string (e.g. 640x320x30)

Author: marmarta

qui/devices/backend.py

@@ -38,6 +38,7 @@
 
 FEATURE_HIDE_CHILDREN = "device-hide-children"
 FEATURE_ATTACH_WITH_MIC = "device-attach-with-mic"
+FEATURE_RESOLUTION = "device-qvc-resolution"  # dev_id=resolution, space delimited
 
 
 class VM:
@@ -163,6 +164,7 @@ def __init__(self, dev: qubesadmin.devices.DeviceInfo, gtk_app: Gtk.Application)
 
         self._data: Dict = getattr(dev, "data", {})
         self._device_id = getattr(dev, "device_id", "*")
+        self.options = {}
         self.parent = str(getattr(dev, "parent_device", None) or "")
         self.attachments: Set[VM] = set()
         self.assignments: Set[VM] = set()
@@ -185,6 +187,20 @@ def __init__(self, dev: qubesadmin.devices.DeviceInfo, gtk_app: Gtk.Application)
         self.show_children: bool = True
         self.hide_this_device: bool = False
 
+        if self.device_class == "webcam" and self._backend_domain:
+            resolution_feature = self._backend_domain.vm_object.features.get(
+                FEATURE_RESOLUTION, ""
+            )
+            if resolution_feature:
+                for w in resolution_feature.split(" "):
+                    try:
+                        k, v = w.split("=")
+                        if k == self.id_string:
+                            self.options["format"] = v
+                    except ValueError:
+                        # malformed options, ignore them
+                        pass
+
     def __str__(self):
         return self._dev_name
 
@@ -285,6 +301,7 @@ def attach_to_vm(self, vm: VM, with_aux_devices: bool = True):
                 port_id=self._ident,
                 devclass=self.device_class,
                 device_id=self._device_id,
+                options=self.options,
             )
             vm.vm_object.devices[self.device_class].attach(assignment)
             self.gtk_app.emit_notification(

qui/devices/device_widget.py

@@ -173,6 +173,13 @@ def __init__(self, app_name, qapp, dispatcher):
         self.dispatcher.add_handler(
             "domain-feature-delete:internal", self.update_internal_feature
         )
+        self.dispatcher.add_handler(
+            "domain-feature-set:" + backend.FEATURE_RESOLUTION, self.update_resolution
+        )
+        self.dispatcher.add_handler(
+            "domain-feature-delete:" + backend.FEATURE_RESOLUTION,
+            self.update_resolution,
+        )
 
         for feature in [backend.FEATURE_HIDE_CHILDREN, backend.FEATURE_ATTACH_WITH_MIC]:
 
@@ -445,6 +452,29 @@ def update_single_feature(self, _vm, _event, feature, value=None, oldvalue=None)
                     self.parent_ports_to_hide.append(dev.port)
                     self.hide_child_devices(dev.port, False)
 
+    def update_resolution(self, vm, _event, feature, value=None, oldvalue=None):
+        # pylint: disable=unused-argument
+        res_dict = {}
+        if value:
+            for word in value.split(" "):
+                try:
+                    k, v = word.split("=")
+                    res_dict[k] = v
+                except ValueError:
+                    # the feature is malformed, ignore it
+                    res_dict = {}
+
+        for device in self.devices.values():
+            if (
+                device.device_class == "webcam"
+                and device.backend_domain.name == vm.name
+            ):
+                resolution = res_dict.get(device.id_string, None)
+                if resolution:
+                    device.options["format"] = resolution
+                elif "format" in device.options:
+                    del device.options["format"]
+
     def vm_unpaused(self, vm, _event, **_kwargs):
         wrapped_vm = backend.VM(vm)
         try: