[PINENTRY PATCH] gnome3: Test if Gcr System Prompter is available at startup.

[Daniel Kahn Gillmor]

* gnome3/pinentry-gnome3.c (gcr_system_prompt_available): new function
  tests whether it is possible to create a GcrSystemPrompt; (main):
  use gcr_system_prompt_available() to decide whether to fall back to
  curses or not.

Debian-bug-id: 842015
Signed-off-by: Daniel Kahn Gillmor <dkg at fifthhorseman.net>
---
 gnome3/pinentry-gnome3.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/gnome3/pinentry-gnome3.c b/gnome3/pinentry-gnome3.c
index d6d7d16..37c7a44 100644
--- a/gnome3/pinentry-gnome3.c
+++ b/gnome3/pinentry-gnome3.c
@@ -258,6 +258,39 @@ gnome3_cmd_handler (pinentry_t pe)
 
 pinentry_cmd_handler_t pinentry_cmd_handler = gnome3_cmd_handler;
 
+
+/* test whether we can create a system prompt or not.  This briefly
+   does create a system prompt, which blocks other tools from making
+   the same concurrent request, so we just create it to test if it is
+   available, and quickly close it.
+*/
+int gcr_system_prompt_available ()
+{
+  GcrSystemPrompt *prompt;
+  GError *error = NULL;
+  int ret = 0;
+  
+  prompt = gcr_system_prompt_open (0, NULL, &error);
+  if (prompt)
+    {
+      ret = 1;
+      if (!gcr_system_prompt_close (prompt, NULL, &error))
+          fprintf (stderr, "failed to close test Gcr System Prompt (%d): %s\n",
+                   error ? error->code : -1, error ? error->message : "<no GError>");
+      g_clear_object (&prompt);
+    }
+  else
+      /* This one particular failure is OK; we're clearly capable of
+         making a system prompt, even though someone else has the
+         system prompter right now: */
+    if (error && error->code == GCR_SYSTEM_PROMPT_IN_PROGRESS)
+      ret = 1;
+
+  if (error)
+    g_error_free (error);
+  return ret;
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -270,6 +303,12 @@ main (int argc, char *argv[])
                " falling back to curses\n");
       pinentry_cmd_handler = curses_cmd_handler;
     }
+  else if (!gcr_system_prompt_available ())
+    {
+      fprintf (stderr, "No Gcr System Prompter available,"
+               " falling back to curses\n");
+      pinentry_cmd_handler = curses_cmd_handler;
+    }      
 #endif
 
   pinentry_parse_opts (argc, argv);
-- 
2.10.1