linux-capture: Watch for VisibilityNotify events

Some window managers like i3 don't issue Expose events when switching
between workspaces, but send VisibilityNotify events. This causes the
stream to freeze even when the workspace is switched back.

Related issue: #863

plugins/linux-capture/xcompcap-helper.cpp

@@ -267,6 +267,9 @@ namespace XCompcap
 			if (ev.type == Expose)
 				changedWindows.insert(ev.xexpose.window);
 
+			if (ev.type == VisibilityNotify)
+				changedWindows.insert(ev.xvisibility.window);
+
 			if (ev.type == DestroyNotify)
 				changedWindows.insert(ev.xdestroywindow.event);
 		}

plugins/linux-capture/xcompcap-main.cpp

@@ -318,7 +318,10 @@ void XCompcapMain::updateSettings(obs_data_t *settings)
 	}
 
 	if (p->win)
-		XSelectInput(xdisp, p->win, StructureNotifyMask | ExposureMask);
+		XSelectInput(xdisp, p->win,
+			StructureNotifyMask
+			| ExposureMask
+			| VisibilityChangeMask);
 	XSync(xdisp, 0);
 
 	XWindowAttributes attr;