QBrush, QPen: Provide explicit comparison for types we compare with

Instead of implicitly creating a QPen or a QBrush from a color or style
just to be able to compare the result with the left-hand side pen or
brush, provide comparesEqual friends that can take a shortcut, avoiding
the allocation that comes with the implicit construction of the types.

operator==(Brush, BrushStyle) needs some extra handling, as we will
create a NoBrush brush if the style alone is not enough anyway.

Change-Id: I06e3d585160ad4fb5d12a46baf8c6a0aaaeeb0b0
Reviewed-by: Christian Ehrlicher <[email protected]>

5 files changed, 68 insertions, 3 deletions

diff --git a/src/gui/painting/qbrush.h b/src/gui/painting/qbrush.h
index ca8112ff31f..b5958f853c3 100644
--- a/src/gui/painting/qbrush.h
+++ b/src/gui/painting/qbrush.h
@@ -82,6 +82,32 @@ private:
     friend struct QSpanData;
     friend class QPainter;
     friend bool Q_GUI_EXPORT qHasPixmapTexture(const QBrush& brush);
+
+    friend bool comparesEqual(const QBrush &lhs, QColor rhs) noexcept
+    {
+        return lhs.color() == rhs && lhs.style() == Qt::SolidPattern
+            && lhs.transform().isIdentity();
+    }
+    Q_DECLARE_EQUALITY_COMPARABLE(QBrush, QColor)
+    Q_DECLARE_EQUALITY_COMPARABLE(QBrush, Qt::GlobalColor)
+
+    friend bool comparesEqual(const QBrush &lhs, Qt::BrushStyle rhs) noexcept
+    {
+        switch (rhs) {
+        case Qt::NoBrush:
+        case Qt::TexturePattern:
+        case Qt::LinearGradientPattern:
+        case Qt::RadialGradientPattern:
+        case Qt::ConicalGradientPattern:
+            // A brush constructed only from one of those styles will end up
+            // using NoBrush (see qbrush_check_type)
+            return lhs.style() == Qt::NoBrush;
+        default:
+            return lhs.style() == rhs && lhs.color() == QColor(0, 0, 0);
+        }
+    }
+    Q_DECLARE_EQUALITY_COMPARABLE(QBrush, Qt::BrushStyle)
+
     void detach(Qt::BrushStyle newStyle);
     void init(const QColor &color, Qt::BrushStyle bs);
     DataPtr d;
diff --git a/src/gui/painting/qpen.cpp b/src/gui/painting/qpen.cpp
index fc151763aac..89dbdc0d3df 100644
--- a/src/gui/painting/qpen.cpp
+++ b/src/gui/painting/qpen.cpp
@@ -199,8 +199,8 @@ QPenPrivate::QPenPrivate(const QBrush &_brush, qreal _width, Qt::PenStyle penSty
     joinStyle = _joinStyle;
 }
 
-static const Qt::PenCapStyle qpen_default_cap = Qt::SquareCap;
-static const Qt::PenJoinStyle qpen_default_join = Qt::BevelJoin;
+static constexpr Qt::PenCapStyle qpen_default_cap = Qt::SquareCap;
+static constexpr Qt::PenJoinStyle qpen_default_join = Qt::BevelJoin;
 
 class QPenDataHolder
 {
@@ -769,7 +769,16 @@ void QPen::setCosmetic(bool cosmetic)
     d->cosmetic = cosmetic;
 }
 
-
+/*!
+    \internal
+*/
+bool QPen::isSolidDefaultLine() const noexcept
+{
+    return d->style == Qt::SolidLine && d->width == 1
+        && d->capStyle == qpen_default_cap && d->joinStyle == qpen_default_join
+        && qFuzzyCompare(d->dashOffset, 0) && qFuzzyCompare(d->miterLimit, 2)
+        && d->cosmetic == false;
+}
 
 /*!
     \fn bool QPen::operator!=(const QPen &pen) const
diff --git a/src/gui/painting/qpen.h b/src/gui/painting/qpen.h
index 3367b96c358..abd5d914628 100644
--- a/src/gui/painting/qpen.h
+++ b/src/gui/painting/qpen.h
@@ -86,6 +86,22 @@ private:
     friend Q_GUI_EXPORT QDataStream &operator>>(QDataStream &, QPen &);
     friend Q_GUI_EXPORT QDataStream &operator<<(QDataStream &, const QPen &);
 
+    bool isSolidDefaultLine() const noexcept;
+
+    friend bool comparesEqual(const QPen &lhs, QColor rhs) noexcept
+    {
+        return lhs.brush() == rhs && lhs.isSolidDefaultLine();
+    }
+    Q_DECLARE_EQUALITY_COMPARABLE(QPen, QColor)
+
+    friend bool comparesEqual(const QPen &lhs, Qt::PenStyle rhs)
+    {
+        if (rhs == Qt::NoPen)
+            return lhs.style() == Qt::NoPen;
+        return lhs == QPen(rhs); // allocates
+    }
+    Q_DECLARE_EQUALITY_COMPARABLE_NON_NOEXCEPT(QPen, Qt::PenStyle)
+
 public:
     using DataPtr = QExplicitlySharedDataPointer<QPenPrivate>;
 
diff --git a/tests/auto/gui/painting/qbrush/tst_qbrush.cpp b/tests/auto/gui/painting/qbrush/tst_qbrush.cpp
index 678c8d9b326..c56fcc8216d 100644
--- a/tests/auto/gui/painting/qbrush/tst_qbrush.cpp
+++ b/tests/auto/gui/painting/qbrush/tst_qbrush.cpp
@@ -90,6 +90,16 @@ void tst_QBrush::operator_eq_eq()
     QFETCH(QBrush, brush2);
     QFETCH(bool, isEqual);
     QCOMPARE(brush1 == brush2, isEqual);
+
+    // exercise operator== overloads
+    QCOMPARE(QBrush(brush1.color()), brush1.color());
+    QCOMPARE(QBrush(brush1.style()), brush1.style());
+    QCOMPARE(QBrush(Qt::black), Qt::black);
+
+    // exercise operator== overloads with implicit construction
+    const QGradient warmFlame = QGradient::WarmFlame;
+    QCOMPARE(QBrush(warmFlame), warmFlame);
+    QCOMPARE(QBrush(QImage()), QImage());
 }
 
 void tst_QBrush::stream_data()
diff --git a/tests/auto/gui/painting/qpen/tst_qpen.cpp b/tests/auto/gui/painting/qpen/tst_qpen.cpp
index b3ff1c76f9e..c9d43663d5c 100644
--- a/tests/auto/gui/painting/qpen/tst_qpen.cpp
+++ b/tests/auto/gui/painting/qpen/tst_qpen.cpp
@@ -155,6 +155,10 @@ void tst_QPen::operator_eq_eq()
     QFETCH(QPen, pen2);
     QFETCH(bool, isEqual);
     QCOMPARE(pen1 == pen2, isEqual);
+
+    // exercise operator== overloads
+    QCOMPARE(QPen(pen1.style()), pen1.style());
+    QCOMPARE(QPen(pen1.color()), pen1.color());
 }