Shoehorn AccentColor into QPalette and keep existing 64bit resolve mask

It is necessary to add an AccentColor role to QPalette.
QPalette currently has 21 color roles and 3 color groups, which
require 63 bits to resolve. The resolve mask is implemented with a
qint64, which doesn't provide spare bits for another color role.

The color role NoRole is used as a default value, marking that a role
has not (yet) been defined. The enum value does not represent a valid
brush, even though it can theoretically be stored in QPalette's shared
data.

This patch adds the enum value AccentColor to QPalette::ColorRole,
increasing the available color roles to 22.
To keep the resolve mask at 63 bits, AccentColor is mapped to NoRole
in static constexpr bitPosition.

As the enum range would exceed 64 bits without this tweak, 3 additional
bits are substracted in the respective static assertion.

With NoRole having no bit in the resolve mask, the following adaptions
have been implemented:
- QPalette::resolve() is adapted to explicitly ignore NoRole.
- QPalette::isBrushSet() always returns false for NoRole.
- tst_QPalette::setAllPossibleBrushes() to verify the latter
- operator== ignores NoRole (documentation updated)

AccentColor is added in tst_QPalette::roleValues and enum documentation
is adapted.

In QPalette's default constructor, the AccentColor brush is defaulting
to the Highlight brush, it this is available. Otherwise it is made 30%
darker or lighter than the Base brush, depending on dark/light mode
heuristics.

QPalette's data stram functions have been extended from QDataStream
Version Qt_6_6. If earlier versions are de-serialised, the AccentColor
defaults to Highlight. An autotest function dataStream() has been added
to tst_QPalette.

The QDataStream Version Qt_6_6 has been bumped to 21.
tst_QDataStream has been adapted to the new version and the new
color Role.

Change-Id: I98bbf9de95fb83bda921e9614a0db3a3c0ebdf75
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/corelib/serialization/qdatastream.h b/src/corelib/serialization/qdatastream.h
index 0942c3ed1d..9e35328de4 100644
--- a/src/corelib/serialization/qdatastream.h
+++ b/src/corelib/serialization/qdatastream.h
@@ -68,7 +68,7 @@ public:
         Qt_6_3 = Qt_6_0,
         Qt_6_4 = Qt_6_0,
         Qt_6_5 = Qt_6_0,
-        Qt_6_6 = Qt_6_0,
+        Qt_6_6 = 21,
         Qt_DefaultCompiledVersion = Qt_6_6
 #if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
 #error Add the datastream version for this Qt version and update Qt_DefaultCompiledVersion