From d1486e2982df9373a7e5816609eff066cac6eb52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@qt.io>
Date: Wed, 4 Sep 2019 12:50:37 +0200
Subject: Simplify QColorSpacePrivate initialization

QColorVector and QColorMatrix are default-constructed following the
Qt philosophy of types always being well-defined. The corner-case where
we need uninitialized versions of these types for performance reasons
is handled explicitly.

Change-Id: I629334d1ffc63563ec9fd1298c623946e0799d1d
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
---
 src/gui/painting/qcolortransform.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

(limited to 'src/gui/painting/qcolortransform.cpp')

diff --git a/src/gui/painting/qcolortransform.cpp b/src/gui/painting/qcolortransform.cpp
index 53fd1dfbaa..10ccefed74 100644
--- a/src/gui/painting/qcolortransform.cpp
+++ b/src/gui/painting/qcolortransform.cpp
@@ -612,6 +612,15 @@ static void storeOpaque(QRgba64 *dst, const QRgba64 *src, const QColorVector *bu
 
 static constexpr qsizetype WorkBlockSize = 256;
 
+template <typename T, int Count = 1>
+class QUninitialized
+{
+public:
+    operator T*() { return reinterpret_cast<T *>(this); }
+private:
+    alignas(T) char data[sizeof(T) * Count];
+};
+
 template<typename T>
 void QColorTransformPrivate::apply(T *dst, const T *src, qsizetype count, TransformFlags flags) const
 {
@@ -623,7 +632,8 @@ void QColorTransformPrivate::apply(T *dst, const T *src, qsizetype count, Transf
 
     bool doApplyMatrix = (colorMatrix != QColorMatrix::identity());
 
-    QColorVector buffer[WorkBlockSize];
+    QUninitialized<QColorVector, WorkBlockSize> buffer;
+
     qsizetype i = 0;
     while (i < count) {
         const qsizetype len = qMin(count - i, WorkBlockSize);
-- 
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