QColorTrcLut: hold in shared_ptr

... instead of raw pointers or QSharedPointer.

Raw pointers are, of course, a no-no in modern code. In particular,
when the result is then held in shared_ptr or QSharedPointer,
make_shared or QSharedPointer::create() should be used to reduce
number of memory allocations.

Since this is private API, we're free to use std::shared_ptr, which
does only half the atomic operations on copies, compared to
QSharedPointer, so is more efficient.

For either make_shared or QSharedPointer::create(), we need to work
around the private ctor, which we do by inheriting a member-function
local class from QColorTrcLut and make_shared'ing that. As a
member-function-local class, it has access to the otherwise private
parts of QColorTrcLut, including its default constructor. As a public
subclass, shared_ptr has no problem performing the derived-to-base
pointer adjustment in the return statement. This way, we can use
make_shared even though our target's class' ctor is private.

Change-Id: Icb11249b54cd5e544e692f6a0bf1f9dda1710454
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 4 insertions, 8 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 101b33f94a..e6bc471ec7 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -4156,10 +4156,8 @@ void QGuiApplicationPrivate::notifyDragStarted(const QDrag *drag)
 const QColorTrcLut *QGuiApplicationPrivate::colorProfileForA8Text()
 {
 #ifdef Q_OS_WIN
-    if (!m_a8ColorProfile){
-        QColorTrcLut *cs = QColorTrcLut::fromGamma(2.31); // This is a hard-coded thing for Windows text rendering
-        m_a8ColorProfile.reset(cs);
-    }
+    if (!m_a8ColorProfile)
+        m_a8ColorProfile = QColorTrcLut::fromGamma(2.31); // This is a hard-coded thing for Windows text rendering
     return m_a8ColorProfile.get();
 #else
     return colorProfileForA32Text();
@@ -4168,10 +4166,8 @@ const QColorTrcLut *QGuiApplicationPrivate::colorProfileForA8Text()
 
 const QColorTrcLut *QGuiApplicationPrivate::colorProfileForA32Text()
 {
-    if (!m_a32ColorProfile) {
-        QColorTrcLut *cs = QColorTrcLut::fromGamma(fontSmoothingGamma);
-        m_a32ColorProfile.reset(cs);
-    }
+    if (!m_a32ColorProfile)
+        m_a32ColorProfile = QColorTrcLut::fromGamma(fontSmoothingGamma);
     return m_a32ColorProfile.get();
 }