[vte] app: Add tooltip with the regex compile error on the search entry

[Christian Persch <chpe src gnome org>]

commit c2a0b3e8bf1c1bfe8709565c3a1d6b099dec7464
Author: Christian Persch <chpe gnome org>
Date:   Sat Dec 26 12:27:22 2015 +0100

    app: Add tooltip with the regex compile error on the search entry
    
    When compiling the regex fails, set the error message as tooltip
    on the search entry; when it succeeds, clear the tooltip.

 src/app.vala    |    3 +++
 src/vteregex.cc |    4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/app.vala b/src/app.vala
index e06d884..0dcb3b9 100644
--- a/src/app.vala
+++ b/src/app.vala
@@ -156,17 +156,20 @@ class SearchPopover : Gtk.Popover
         }
 
         regex_pattern = pattern;
+        search_entry.set_tooltip_text(null);
       } catch (Error e) {
 #if WITH_PCRE2
         regex = null;
 #endif
         gregex = null;
+        search_entry.set_tooltip_text(e.message);
       }
     } else {
 #if WITH_PCRE2
       regex = null;
 #endif
       gregex = null;
+      search_entry.set_tooltip_text(null);
     }
 
 #if WITH_PCRE2
diff --git a/src/vteregex.cc b/src/vteregex.cc
index 4b56b37..16dc0fa 100644
--- a/src/vteregex.cc
+++ b/src/vteregex.cc
@@ -191,9 +191,9 @@ vte_regex_new(const char *pattern,
                                &errcode, &erroffset,
                                NULL);
 
-        if (code == 0) {
+        if (code == nullptr) {
                 set_gerror_from_pcre_error(errcode, error);
-                g_prefix_error(error, "Failed to compile pattern to regex at %" G_GSIZE_FORMAT ":",
+                g_prefix_error(error, "Failed to compile pattern to regex at offset %" G_GSIZE_FORMAT ":",
                                erroffset);
                 return NULL;
         }