helper: Show confirmation overlay before displaying any media.

zulipterminal/helper.py

@@ -5,7 +5,7 @@
 import sys
 import time
 from collections import OrderedDict, defaultdict
-from functools import wraps
+from functools import partial, wraps
 from itertools import chain, combinations
 from re import ASCII, match
 from tempfile import gettempdir
@@ -17,6 +17,7 @@
 
 import lxml.html
 import requests
+import urwid
 from mypy_extensions import TypedDict
 
 
@@ -677,4 +678,7 @@ def open_media(controller: Any, media_link: str, message_id: int) -> None:
         'darwin': 'open',
     }
     command = image_viewers[sys.platform]
-    subprocess.run([command, img_path])
+    callback = partial(subprocess.run, [command, img_path])
+    question = urwid.Text("Your requested media has been downloaded."
+                          " Do you want to view it?")
+    controller.show_confirmation_overlay(question, callback)