virt-manager: reset vgamem for video when changing device type

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1169295

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

tests/xmlparse-xml/change-videos-out.xml

@@ -30,7 +30,7 @@
       <model type="vmvga" heads="5"/>
     </video>
     <video>
-      <model type="qxl" ram="100"/>
+      <model type="qxl" vgamem="8192" ram="100"/>
     </video>
   </devices>
 </domain>

tests/xmlparse.py

@@ -628,6 +628,7 @@ class XMLParseTest(unittest.TestCase):
         check = self._make_checker(dev3)
         check("model", "cirrus", "cirrus", "qxl")
         check("ram", None, 100)
+        check("vgamem", None, 8192)
 
         self._alter_compare(guest.get_xml_config(), outfile)
 

virtManager/domain.py

@@ -860,6 +860,7 @@ class vmmDomain(vmmLibvirtObject):
             editdev.vram = None
             editdev.heads = None
             editdev.ram = None
+            editdev.vgamem = None
 
         return self._redefine_device(change, devobj, use_live_device)
 

virtinst/devicevideo.py

@@ -35,14 +35,14 @@ class VirtualVideoDevice(VirtualDevice):
             return model.upper()
         return model.capitalize()
 
-
-    _XML_PROP_ORDER = ["model", "vram", "heads"]
+    _XML_PROP_ORDER = ["model", "vram", "heads", "vgamem"]
     model = XMLProperty("./model/@type",
                         default_cb=lambda s: "cirrus",
                         default_name=MODEL_DEFAULT)
     vram = XMLProperty("./model/@vram", is_int=True)
     ram = XMLProperty("./model/@ram", is_int=True)
     heads = XMLProperty("./model/@heads", is_int=True)
+    vgamem = XMLProperty("./model/@vgamem", is_int=True)
 
 
 VirtualVideoDevice.register_type()