xcb: Wrap xcb callings in macros

... to improve readability and reliability.

This change introduces macros Q_XCB_REPLY and Q_XCB_REPLY_UNCHECKED
that allow to replace couples of xcb cookie/reply callings by
a single "calling" of a macro. The macros wrap the reply in
std::unique_ptr thus preventing the need to free it manually.

The following C++11 features are used:
  - variadic macros
  - std::unique_ptr
  - auto type deduction

Change-Id: Icf9b93353404a39bf5f4a4562b9234db18cac696
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index 7f0d5cf2cc..c298c08322 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -56,6 +56,8 @@
 #include <QtCore/QLoggingCategory>
 #include <QtCore/private/qglobal_p.h>
 
+#include <memory>
+
 // This is needed to make Qt compile together with XKB. xkb.h is using a variable
 // which is called 'explicit', this is a reserved keyword in c++
 #if QT_CONFIG(xkb)
@@ -731,6 +733,20 @@ private:
     QXcbConnection *m_connection;
 };
 
+#define Q_XCB_REPLY_CONNECTION_ARG(connection, ...) connection
+
+#define Q_XCB_REPLY(call, ...) \
+    std::unique_ptr<call##_reply_t, decltype(std::free) *>( \
+        call##_reply(Q_XCB_REPLY_CONNECTION_ARG(__VA_ARGS__), call(__VA_ARGS__), nullptr), \
+        std::free \
+    )
+
+#define Q_XCB_REPLY_UNCHECKED(call, ...) \
+    std::unique_ptr<call##_reply_t, decltype(std::free) *>( \
+        call##_reply(Q_XCB_REPLY_CONNECTION_ARG(__VA_ARGS__), call##_unchecked(__VA_ARGS__), nullptr), \
+        std::free \
+    )
+
 #ifdef Q_XCB_DEBUG
 template <typename cookie_t>
 cookie_t q_xcb_call_template(const cookie_t &cookie, QXcbConnection *connection, const char *file,