QPen/QBrush: de-inline compare helper functions

These functions expose implementation details of their respective
class, so, seeing as the classes are pimpl'ed and their op==s are
out-of-line, too, these functions ought to be out-of-line, too.

De-inline them, by calling a private out-of-line helper function. This
way, they can remain unexported and "real" hidden friends (= with an
inline definition).

As drive-by:

- in QBrush/QColor: check the properties in the order of cheapness
  (style(), color(), transform()), and don't copy QTransform just to
  check isIdentity() (access the member directly).

- in QPen/QColor: avoid the QBrush copy (access the member
  directly). This also retroactively endorses the noexcept on this
  function.

- in QPen/PenStyle: amend the comment that says it's allocating with a
  `// ### optimize`

Amends f0186862e16128343705abd0de5994e8ca05a909.

Found in API-review.

Pick-to: 6.9
Change-Id: Ibfd43b1f2200ef030d6739dad1bf026cc190606b
Reviewed-by: Tatiana Borisova <tatiana.borisova@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/painting/qbrush.cpp

@@ -974,6 +974,33 @@ bool QBrush::operator==(const QBrush &b) const
     }
 }
 
+/*!
+    \internal
+*/
+bool QBrush::doCompareEqualColor(QColor rhs) const noexcept
+{
+    return style() == Qt::SolidPattern && color() == rhs && d->transform.isIdentity();
+}
+
+/*!
+    \internal
+*/
+bool QBrush::doCompareEqualStyle(Qt::BrushStyle rhs) const 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 style() == Qt::NoBrush;
+    default:
+        return style() == rhs && color() == QColor(0, 0, 0);
+    }
+}
+
 #ifndef QT_NO_DEBUG_STREAM
 /*!
   \internal

src/gui/painting/qbrush.h

@@ -86,28 +86,18 @@ private:
     friend class QPainter;
     friend bool Q_GUI_EXPORT qHasPixmapTexture(const QBrush& brush);
 
+    bool doCompareEqualColor(QColor rhs) const noexcept;
     friend bool comparesEqual(const QBrush &lhs, QColor rhs) noexcept
     {
-        return lhs.color() == rhs && lhs.style() == Qt::SolidPattern
-            && lhs.transform().isIdentity();
+        return lhs.doCompareEqualColor(rhs);
     }
     Q_DECLARE_EQUALITY_COMPARABLE(QBrush, QColor)
     Q_DECLARE_EQUALITY_COMPARABLE(QBrush, Qt::GlobalColor)
 
+    bool doCompareEqualStyle(Qt::BrushStyle rhs) const noexcept;
     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);
-        }
+        return lhs.doCompareEqualStyle(rhs);
     }
     Q_DECLARE_EQUALITY_COMPARABLE(QBrush, Qt::BrushStyle)
 

src/gui/painting/qpen.cpp

@@ -856,6 +856,23 @@ bool QPen::operator==(const QPen &p) const
             && p.d->cosmetic == d->cosmetic);
 }
 
+/*!
+    \internal
+*/
+bool QPen::doCompareEqualColor(QColor rhs) const noexcept
+{
+    return d->brush == rhs && isSolidDefaultLine();
+}
+
+/*!
+    \internal
+*/
+bool QPen::doCompareEqualStyle(Qt::PenStyle rhs) const
+{
+    if (rhs == Qt::NoPen)
+        return style() == Qt::NoPen;
+    return *this == QPen(rhs); // ### optimize (allocates)
+}
 
 /*!
     \fn bool QPen::isDetached()

src/gui/painting/qpen.h

@@ -91,17 +91,17 @@ private:
 
     bool isSolidDefaultLine() const noexcept;
 
+    bool doCompareEqualColor(QColor rhs) const noexcept;
     friend bool comparesEqual(const QPen &lhs, QColor rhs) noexcept
     {
-        return lhs.brush() == rhs && lhs.isSolidDefaultLine();
+        return lhs.doCompareEqualColor(rhs);
     }
     Q_DECLARE_EQUALITY_COMPARABLE(QPen, QColor)
 
+    bool doCompareEqualStyle(Qt::PenStyle rhs) const;
     friend bool comparesEqual(const QPen &lhs, Qt::PenStyle rhs)
     {
-        if (rhs == Qt::NoPen)
-            return lhs.style() == Qt::NoPen;
-        return lhs == QPen(rhs); // allocates
+        return lhs.doCompareEqualStyle(rhs);
     }
     Q_DECLARE_EQUALITY_COMPARABLE_NON_NOEXCEPT(QPen, Qt::PenStyle)