Qt: Add and use qUtf8Printable.

Qt 5.4 introduced qUtf8Printable, a convenience macro for converting
QString to a UTF-8 const char *. Add a compatibility definition and
start using it.

Change-Id: I3cf88611b1ed1a34082cb2ba82394954e2e6c461
Reviewed-on: https://code.wireshark.org/review/24828
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/docbook/wsdg_src/WSDG_chapter_userinterface.asciidoc b/docbook/wsdg_src/WSDG_chapter_userinterface.asciidoc
index fd906a3ada..ce2a070a63 100644
--- a/docbook/wsdg_src/WSDG_chapter_userinterface.asciidoc
+++ b/docbook/wsdg_src/WSDG_chapter_userinterface.asciidoc
@@ -163,12 +163,19 @@ it's not strictly required:
 
 ===== Strings
 
-If you're using GLib string functions or plain old C character array idioms in
-Qt-only code you're probably doing something wrong. QStrings are generally
-*much* safer and easier to use. They also make translations easier.
+Wireshark's C code and GLib use UTF-8 encoded character arrays. Qt
+(specifically QString) uses UTF-16. You can convert a `char *` to a
+`QString` using simple assignment. You can convert a `QString` to a
+`const char *` using `qUtf8Printable`.
+
+If you're using GLib string functions or plain old C character array
+idioms in Qt-only code you're probably doing something wrong,
+particularly if you're manually allocating and releasing memory.
+QStrings are generally *much* safer and easier to use. They also make
+translations easier.
 
 If you need to pass strings between Qt and GLib you can use a number
-of convenience routines which  are defined in 'ui/qt/qt_ui_utils.h'.
+of convenience routines which are defined in 'ui/qt/qt_ui_utils.h'.
 
 If you're calling a function that returns wmem-allocated memory it might make
 more sense to add a wrapper function to 'qt_ui_utils' than to call wmem_free in