Optimize the QPalette::resolve from the other palette

If all the palette's colors are resolved, nothing needs to be done in
QPalette::resolve(const QPalette &other).

Change-Id: I1573cfa5b5cd1e7eb15f3242aff6ab92e9f8c84b
Reviewed-by: Qt CI Bot <[email protected]>
Reviewed-by: Volker Hilsheimer <[email protected]>

2 files changed, 22 insertions, 0 deletions

diff --git a/src/gui/kernel/qpalette.cpp b/src/gui/kernel/qpalette.cpp
index 22ba5f3bcd3..5a0bad91599 100644
--- a/src/gui/kernel/qpalette.cpp
+++ b/src/gui/kernel/qpalette.cpp
@@ -921,6 +921,17 @@ qint64 QPalette::cacheKey() const
     return (((qint64) d->ser_no) << 32) | ((qint64) (d->detach_no));
 }
 
+static constexpr QPalette::ResolveMask allResolveMask()
+{
+    QPalette::ResolveMask mask = {0};
+    for (int role = 0; role < int(QPalette::NColorRoles); ++role) {
+        for (int grp = 0; grp < int(QPalette::NColorGroups); ++grp) {
+            mask |= (QPalette::ResolveMask(1) << bitPosition(QPalette::ColorGroup(grp), QPalette::ColorRole(role)));
+        }
+    }
+    return mask;
+}
+
 /*!
     Returns a new QPalette that is a union of this instance and \a other.
     Color roles set in this instance take precedence.
@@ -934,6 +945,9 @@ QPalette QPalette::resolve(const QPalette &other) const
         return o;
     }
 
+    if (d->resolveMask == allResolveMask())
+        return *this;
+
     QPalette palette(*this);
     palette.detach();
 
diff --git a/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp b/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
index 9ef313f36db..5baec3c180c 100644
--- a/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
+++ b/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
@@ -122,6 +122,14 @@ void tst_QPalette::resolve()
 
     QVERIFY(p2ResolvedTo1 != p1);
     QVERIFY(p2ResolvedTo1 != p2);
+
+    QPalette p3;
+    // ensure the resolve mask is full
+    for (int r = 0; r < QPalette::NColorRoles; ++r)
+        p3.setBrush(QPalette::All, QPalette::ColorRole(r), Qt::red);
+
+    QPalette p3ResolvedToP1 = p3.resolve(p1);
+    QVERIFY(p3ResolvedToP1.isCopyOf(p3));
 }